Mutations in the CRB1 gene cause Leber congenital amaurosis

OBJECTIVES

To test the hypothesis that mutations in the CRB1 gene cause Leber congenital amaurosis (LCA) and, if so, to describe the ocular phenotype of patients with LCA who harbor CRB1 sequence variations.

PATIENTS

One hundred ninety probands with a clinical diagnosis of LCA were selected from a cohort of 233 probands ascertained in 5 different countries. The remaining 43 probands (18%) were excluded because they harbored sequence variations in previously identified LCA genes.

METHODS

One hundred ninety unrelated individuals with LCA were screened for coding sequence mutations in the CRB1 gene with single-strand conformation polymorphism analysis followed by automated DNA sequencing.

RESULTS

Twenty-one of the 190 probands (9% of the total cohort of 233) and 2 (1.4%) of 140 controls harbored amino acid-altering sequence variations in the CRB1 gene (P =.003).

CONCLUSIONS

In our cohort of patients with LCA, coding sequence variations were observed in the CRB1 gene more frequently than in any of the other 5 known LCA-associated genes. Likely disease-causing sequence variations have now been identified in 64 (28%) of 233 subjects in this cohort.

CLINICAL RELEVANCE

Molecular diagnosis can confirm and clarify the diagnosis in an increasing fraction of patients with LCA. As genotype data accumulate, clinical phenotypes associated with specific mutations may be established. This will facilitate the counseling of patients regarding their visual prognosis and the likelihood of associated systemic anomalies.

Rod-mediated increment threshold functions in infants

PURPOSE

To obtain and analyze scotopic increment threshold functions to test the hypothesis that rod photoreceptor immaturity accounts for the elevation of infants' over controls' dark-adapted thresholds and elevation of parafoveal over peripheral thresholds in infants.

METHODS

Using a preferential looking method, thresholds for detection of 2(o), 50 msec, blue stimuli presented 10(o) (parafoveal) or 30(o) (peripheral) eccentric were measured in the dark and in the presence of steady red backgrounds. Ten 10-week-old infants and four control subjects (8-35 years) were tested. To evaluate pre- and postadaptation site determinants of threshold, a model of the increment threshold function was fit to the data, and the dark-adapted threshold (T(D)) and eigengrau (A(O)) were calculated. The values of T(D) and A(O) were compared between infants and controls and between parafoveal and peripheral eccentricities.

RESULTS

At both parafoveal and peripheral eccentricities, infants' values of T(D) and A(O) were significantly higher than those of controls. The locus of the coordinates (A(O), T(D)) differed significantly between parafoveal and peripheral eccentricities. In every infant, the parafoveal value of T(D) was higher (by 0.3-0.6 log unit) and A(O) lower (by 0.2-0.5 log unit) than the peripheral value, whereas controls had no difference in T(D) and A(O) at the two eccentricities.

CONCLUSIONS

The results indicate that both receptoral and postreceptoral immaturities have a role in the elevation of infants' over controls' thresholds. In infants, rod photoreceptor immaturity before the site of adaptation accounts for elevation of parafoveal over peripheral thresholds.

Rod and rod mediated function in patients with beta-thalassemia major

An electroretinographic (ERG) study was undertaken to test the hypothesis that scotopic retinal function is altered in transfused thalassemics on chronic Deferoxamine (DFO). ERG a- and b-wave responses and dark adapted visual thresholds were obtained from 11 patients with beta-thalassemia major, ages 7 to 38 (median 17) years. A quantitative model of the activation of phototransduction was fitted to the a-waves to estimate the gain of the transduction processes and the saturated amplitude of the rod photoresponse. From b-wave stimulus/response functions. the saturated b-wave amplitude and an index of b-wave sensitivity (log sigma ) were calculated. The patients' data were compared to those of normal subjects. The relations of the ERG parameters to age. average ferritin level, and duration of transfusion without DFO as well as other clinical parameters were examined. Longitudinal measures of b-wave responses and dark adapted visual thresholds. available for nine of the patients, were examined for significant change over time. For all patients both the gain and saturated amplitude of the rod response are normal. In two patients log sigma is below the 99% prediction interval for normal. One has low scotopic visual sensitivity. The duration of transfusion therapy unprotected by DFO chelation therapy was correlated with log a. These results suggest iron accumulation rather than DFO toxicity underlies scotopic dysfunction in older thalassemics. some of whom may have had extended periods of transfusion without the protection of chelation. Thus, monitoring of retinal function is recommended in such patients.

Misdirected vimentin messenger RNA alters cell morphology and motility

Localized messenger RNAs were first observed as embryonic determinants that altered development when mislocalized. In recent years localized mRNAs have been found for several cytoskeletal proteins, including actin, vimentin and several microtubule associated proteins. We sought to determine whether redirecting mRNA for a cytoskeletal protein to an inappropriate address would alter cellular phenotypes. To do so we generated vimentin mRNAs with a myc epitope tag and the (beta)-actin 3′ untranslated region (3′ UTR) as a localization signal. When misdirected vimentin mRNAs are expressed in either fibroblasts or SW13 cells, cells develop numerous, extremely long processes; these cells also move more slowly to enter a wound of the monolayer. In situ hybridization revealed that the misdirected mRNA was often localized in the processes, in contrast to endogenous vimentin mRNA. The processes usually contained actin distal to the transgenic vimentin and microtubules proximal to it. SW13 cells lacking vimentin produced fewer and shorter processes, suggesting a dominant negative effect that involves recruitment of endogenous vimentin. Control experiments that transfected in constructs expressing tagged, correctly localized vimentin, or (beta)-galactosidase that localized through the (beta)-actin 3′ UTR, indicate that neither the shape nor the motility changes are solely due to the level of vimentin expression in the cell. This is direct evidence that the site of expression for at least one cytoskeletal mRNA alters the phenotype of the cell in which it is expressed. Messenger RNA localization is proving to be as essential for the normal maintenance of somatic cell phenotypes as embryonic determinants are for embryogenesis.

The development of scotopic sensitivity

PURPOSE. Test the hypothesis that the developmental increases in rod photoreceptor sensitivity and rod-mediated visual sensitivity at 10 degrees, 20 degrees , and 30 degrees eccentric are concurrent. It is known that maturation of the parafoveal (10 degrees eccentric) rod outer segments and visual sensitivity is delayed compared to that at 30 degrees eccentric.

METHODS

Rod isolated electroretinographic (ERG) responses to full-field stimuli were obtained from dark-adapted subjects (n = 71), ranging in age from early infancy through middle age. Rod photoreceptor sensitivity was calculated by fitting a model of the activation of phototransduction to the a-wave response. Rod driven b-wave sensitivity was calculated from stimulus-response functions. A logistic growth model was used to summarize the developmental increases in sensitivity of the rod photoreceptors and the b-wave. Previously reported dark-adapted, rod-mediated visual sensitivities at 10 degrees , 20 degrees, and 30 degrees eccentric, obtained using preferential looking procedures, were reanalyzed using the logistic growth model.

RESULTS

The logistic growth model accounted for 57% to 85% of the variance of each sensitivity parameter with age in normal subjects. The shape of the growth curve and the age at which sensitivity reaches 50% of the adult value is similar (10.0-13.5 weeks) for the rods, the b-wave, and peripheral visual sensitivity, but is significantly older, 19.5 weeks, for rod-mediated parafoveal visual sensitivity.

CONCLUSIONS

Rod photoreceptor sensitivity and peripheral, rod-mediated visual sensitivity develop concurrently. A parsimonious explanation is that rod photoreceptor sensitivity determines dark-adapted, rod-mediated visual sensitivity during development.

Background adaptation in children with a history of mild retinopathy of prematurity

PURPOSE

In children with a history of mild retinopathy of prematurity (ROP), test the hypothesis that elevation of the parafoveal over peripheral dark-adapted threshold is due to photoreceptor rather than postreceptor dysfunction.

METHODS

A forced choice procedure was used to measure thresholds, for detection of 2 degrees diameter, 50 msec, blue stimuli presented 10 degrees (parafoveal) or 30 degrees (peripheral) eccentric in the dark and in the presence of steady red backgrounds (-4 to +2 log scot td). Four ROP and four control subjects were tested at both eccentricities. A model of the increment threshold function was fit to the data to calculate the eigengrau and dark-adapted threshold.

RESULTS

Both ROP subjects with elevated parafoveal thresholds also have elevated parafoveal eigengraus. On the other hand, parafoveal and peripheral eigengraus are equal in ROP subjects without parafoveal threshold elevation. Nevertheless, the dark-adapted thresholds of all ROP subjects are higher than those of any control subject at both sites.

CONCLUSIONS

The parafoveal threshold elevation is due to rod dysfunction. There is also evidence of peripheral rod photoreceptor involvement in the subjects with ROP.

Muscle-specific transcription factors in fibroblasts expressing the alpha-striated tropomyosin 3' untranslated region

The alpha-striated tropomyosin 3' untranslated region (TM UTR) promotes differentiation of fibroblasts into cells resembling skeletal muscle. To investigate the mechanism of this observation, RNA harvested from transfected primary fibroblasts was used for semiquantitative RT-PCR with primers specific for muscle transcription factors, showing that myoD and myogenin transcripts are detected in these cells, but that differentiation after TM UTR expression is independent of a detectable increase in these transcripts. Double immunofluorescent staining with antibodies to myoD family members and to titin confirms that muscle differentiation in TM UTR-transfected fibroblasts is independent of production of any transcription factor in this family. In contrast, the muscle transcription factor myocyte enhancer factor 2 (mef-2) is strongly expressed after transfection of fibroblasts with the TM UTR. The increase in mef-2 protein is due to an increase in the steady-state level of its mRNA, as shown by Northern analysis. The expression of p21 ordinarily observed in skeletal myogenesis before the expression of muscle-specific proteins is not seen in fibroblasts induced to differentiate by the TM UTR. These results demonstrate that post-transcriptional regulation of myoD family members is seen in fibroblasts, and that the TM UTR induces muscle differentiation independent of the myoD transcription factors and without expressing proteins characteristic of terminal withdrawal from the cell cycle. Finally, an increase in the steady-state level of mef-2 transcripts appears in the proximal pathway of myogenic activation in response to expression of the TM UTR. These results imply that fibroblasts can utilize an additional differentiation route upon TM UTR expression resulting in mature muscle other than that requiring myoD family members.

The course of maturation of rod-mediated visual thresholds in infants

PURPOSE

To measure the developmental course of infants' rod-mediated thresholds.

METHODS

Thresholds for detecting stimuli (2 degrees diameter, 50 msec duration) presented at 10 degrees (parafoveal site) or 30 degrees (peripheral site) from a central fixation target were estimated using a preferential-looking method. Nine infants were tested at both stimulus positions at ages 10, 18, and 26 weeks.

RESULTS

At 10 weeks, infants' thresholds at both sites were significantly higher than those of adults. The infants' average threshold at 10 degrees was 0.5 log unit higher than the infants' average threshold at 30 degrees. Adults' thresholds at the two sites were equal. Thresholds of all infants decreased with age until by age 26 weeks the parafoveal and peripheral thresholds were equal and were the same as those of adults. The rate of change of parafoveal thresholds was significantly faster than the rate of change of peripheral thresholds.

CONCLUSIONS

Although postreceptoral factors cannot be ruled out, the results suggest that developmental increases in rod outer segment length and rhodopsin density account for most of the threshold changes during infancy.

The rhodopsin content of human eyes

PURPOSE

To measure the total amount of rhodopsin in human eyes across the life span and to test the hypothesis that the rhodopsin content of infants' and the elderly's eyes is lower than at other ages.

METHODS

Rhodopsin was extracted from retinal and pigment epithelial fractions of 196 eyes of 102 donors, ages 27 weeks' gestation through 94 years, using quantitative procedures. To recover photopigment bleached by unavoidable light exposure, the fractions from 78 eyes were incubated with 9-cis retinal. The total photopigment (retinal plus pigment epithelial fractions) per eye was examined for significant changes with age, using the higher value from pairs of eyes.

RESULTS

The median rhodopsin content of the higher eye of adults is 6.45 nmoles (range, 3.33-10.84 nmoles) with 8 nmoles or more recovered from 28% of all adult eyes. The rhodopsin content of infants' eyes (< 12 months post-term) is significantly lower than that of older individuals and increases with age. After infancy, no change with age is found. For both infants and adults, 9-cis retinal significantly increases the amount of photopigment recovered without reducing the variance in the amount of photopigment recovered. The rhodopsin content is estimated to be 50% of the median adult amount early in infancy, approximately 5 weeks postterm (95% confidence interval, 0-10 weeks postterm).

CONCLUSIONS

A developmental increase in rhodopsin content occurs during infancy. Thereafter rhodopsin content remains constant. The amount of rhodopsin recovered from human eyes is quite variable. Bleaching alone cannot explain the variability.

Rod photoreceptor maturation does not vary with retinal eccentricity in mammalian retina

PURPOSE

Test the hypothesis that the development of mammalian rod outer segments (ROS) varies with retinal eccentricity.

METHODS

During the period of photoreceptor cell development, ROS lengths, opsin mRNA and (rhod)opsin were measured in central and peripheral retina of cows and pigmented rats. Published ROS length and/or rhodopsin data from albino rats, cows and monkeys were re-analyzed. Logistic growth curves were fitted to the newly obtained and published data. Within a species, growth in central and peripheral regions was compared.

RESULTS

The logistic growth curves fit all the data well and provide an excellent view of the developmental increases in ROS length, opsin mRNA and (rhod)opsin in each retinal region. Within a species, the growth curves for ROS length, opsin mRNA and (rhod)opsin concentration are superimposable. The age at which ROS length reaches 50% of its adult value is invariant with eccentricity. An exception to this pattern is the simian parafoveal ROS, which appears to have a delayed course of development.

CONCLUSIONS

The hypothesis is disproved. Unlike rod photoreceptor cell genesis, ROS development is invariant with retinal eccentricity. Primate parafoveal ROS appear to have a different pattern of development.

Rod photoreceptors in infant rats with a history of oxygen exposure

PURPOSE

To study in an infant rat model of retinopathy of prematurity, the rod photoreceptors, which are known to have attenuated photoresponses.

METHODS

Rhodopsin was extracted from whole retinas, the thickness of the rod outer segment (ROS) layer was measured, large phagosomes were counted, and the ROS ultrastructure was examined in the retinas of oxygen-exposed and control rats, ages 13 and 18 days. Rhodopsin absorbances in the ROS were measured by microspectrophotometry at age 20 days.

RESULTS

The rhodopsin content did not differ significantly between the oxygen-exposed and control rats at either 13 or 18 days. The thickness of the ROS layer was equal in 13-day-old oxygen-exposed and control rats; however, at 18 days, the ROS layer was significantly thinner in the oxygen-exposed rats than in the control rats. The number of phagosomes did not vary significantly among the oxygen-exposed and control groups. Opsin immunoreactivity was seen only in the ROS layer in oxygen-exposed and control rats. The ROS were disorganized in oxygen-exposed rats. The rhodopsin absorbances of the oxygen-exposed ROS were significantly more variable and higher than in the control rats.

CONCLUSIONS

Attenuation of the rod photoresponse parameters does not result simply from shortening of the outer segments and consequent low rhodopsin content. Rather, the structure of the outer segments is altered. A fault in the synthesis of the outer segments, rather than disposal of outer segment discs, is suspected.

Assembly of tropomyosin isoforms into the cytoskeleton of avian muscle cells

Tropomyosin (TM) is a component of microfilaments of most eukaryotic cells. In striated muscle, TM helps confer calcium sensitivity to the actin-myosin interaction. TM is a fibrillar, self-associating protein that binds to the extended actin filament system. We hypothesized that these structural features would permit TM to undergo assembly into the cytoskeleton during translation, or cotranslational assembly. Pulse-chase experiments with [35S]methionine and pulse experiments with [3H]puromycin followed by extraction and immunoprecipitation of TM were performed to examine the mechanism of assembly of TM into the cytoskeleton in cultured avian muscle cells. Pulse-chase experiments provide kinetic evidence for cotranslational assembly of TM in skeletal and cardiac muscle. Demonstration of a large majority of completed TM on purified skeletal muscle microfilaments after a short labeling period confirms that these kinetic data are not related to trapping of TM within the actin network of the cytoskeleton. Nascent TM peptides are demonstrated on the cytoskeleton of muscle cells after a short metabolic pulse followed by puromycin treatment to release nascent peptides from ribosomes or after labeling with [3H]puromycin. Nascent chain localization to the cytoskeleton independent of ribosomal attachment further confirms the high degree of cotranslational assembly of this protein. The extent of cotranslational assembly is similar before and after the formation of significant myofibril in myotubes, suggesting that cotranslational assembly of TM is active during contractile apparatus assembly in muscle differentiation. This is the first report where assembly mechanism has been predicted to be cotranslational based upon structural features of a cytoskeletal protein.

Mutations in the RPE65 gene in patients with autosomal recessive retinitis pigmentosa or leber congenital amaurosis

RPE65 is a protein of unknown function expressed specifically by the retinal pigment epithelium. We examined all 14 exons of this gene in 147 unrelated patients with autosomal recessive retinitis pigmentosa (RP), in 15 patients with isolate RP, and in 45 patients with Leber congenital amaurosis (LCA). Sequence anomalies that were likely to be pathogenic were found in two patients with recessive RP, in one patient with isolate RP recategorized as recessive, and in seven patients with LCA. Cosegregation analysis in each available family showed that all affected individuals were either homozygotes or compound heterozygotes and that all unaffected individuals were either heterozygote carriers or homozygous wild type. In one family, there was one instance of a new mutation not present in either parent of the affected individual. In another family, affected members with recessive RP in three branches (i.e., three distinct pairs of parents) were compound heterozygotes for the same two mutations or homozygous for one of them. Based on our results, mutations in the RPE65 gene appear to account for approximately 2% of cases of recessive RP and approximately 16% of cases of LCA.

Dark-adapted thresholds in children with histories of mild retinopathy of prematurity

PURPOSE

To test the hypothesis that rod-mediated visual thresholds at 10 degrees eccentricity are elevated in children with histories of mild retinopathy of prematurity (ROP).

METHODS

Dark-adapted thresholds for detection of 50 msec, 2 degrees diameter spots at a 10 degrees eccentric site, and at a peripheral reference site, 30 degrees eccentric, were measured in 20 children with a history of mild ROP and known courses of refractive development. Ten myopic control subjects also were tested. The thresholds of the ROP and control subjects were compared.

RESULTS

Six of the subjects with ROP had elevated thresholds at the 10 degrees site. High myopia had been present since age 18 months or younger in each of the six. The thresholds of all other subjects with ROP, whose courses of refractive development had been toward emmetropia, and the control subjects with myopia were normal. In subjects with ROP, the association of early, persistent high myopia and an elevated threshold at 10 degrees was significant (chi 2 = 20; P < 0.01). Among the subjects with ROP, refractive error and axial length were correlated.

CONCLUSIONS

ROP or factors causing ROP appear to alter rod-mediated retinal function. The association of abnormal rod-mediated sensitivity and refractive development suggests that rod-mediated retinal function is involved in the regulation of eye growth in children with a history of mild ROP.

Organization of protein and mRNA for titin and other myofibril components during myofibrillogenesis in cultured chicken skeletal muscle

Myofibril assembly requires the cell to join diverse components, correctly oriented to the rest of the cell. Titin, a huge elastic protein with a role in myogenesis, assembles during translation in vivo and may require spatially organized mRNA to allow assembly. By immunofluorescence, we examined titin and myosin protein organization early in skeletal muscle development in vitro; titin was the first organized, initially as spots, then as periodically spaced lines, and later as doublets. Titin mRNA organization during development was detected by fluorescent in situ hybridization. Only titin mRNA was seen in mononucleated myoblasts. Shortly after fusion, both titin protein and mRNA were diffuse. Titin mRNA remained diffuse when titin protein formed cables. Where titin protein formed linear arrays of spots, titin mRNA showed a colinear, continuous array. Titin mRNA remained in arrays colinear with young myofibrils until several slender myofibrils aligned laterally; then, titin mRNA formed periodic arrays. The titin probe encodes peptide sequence in the A band, where this region of titin mRNA is detected in the most organized cells. Nebulin undergoes a similar progression slightly later in development. This pattern, of narrowly spaced stripes, is too closely spaced to function in the soluble phase. Titin mRNA is the earliest mRNA to become so highly organized in muscle; it does so earlier and at a different location than do mRNAs for costamere proteins. These results, taken with earlier ones, suggest mRNA localization may be as key to somatic cell differentiation as it is to embryonic development.

Rhodopsin in immature rod outer segments

PURPOSE

To test the hypothesis that rhodopsin concentration is low in immature rat rod outer segments (ROS).

METHODS

Microspectrophotometry (MSP) was used to assess rhodopsin absorbances in localized regions of isolated ROS from dark-adapted 13-, 19-, and 34-day-old and adult rats. Photopigment was extracted from the retinas of paired eyes in dark-adapted and light-adapted rats. One retina of each pair was treated with 9-cis retinal before extraction of photopigment. Rhodopsin with native 11-cis retinal was extracted from the fellow retina.

RESULTS

By MSP, rhodopsin absorbance was low in the short ROS of 13-day-old rats. In 19-day-old rats with ROS lengths approximately equal to those of adults, absorbance was low at the tip, but at the base, it was equal to the high absorbance at both the tip and the base in adults. The 9-cis retinal did not add absorbance to the photopigment extracts of dark-adapted retinas at any age, but it did add absorbance to extracts of the light-adapted retinas at every age.

CONCLUSIONS

The MSP results show that the accumulation of rhodopsin in developing rat rods depends on increasing concentrations in localized regions. No evidence of apo-opsin is found in immature rat rods. Thus, in immature ROS regions, the low rhodopsin absorbances suggest that the amount of opsin is also low. Greater disk-to-disk spacing in immature ROS regions than in mature regions could account for these findings.

Vision in Leber congenital amaurosis

OBJECTIVE

To determine if vision changed with age in infants and children with Leber congenital amaurosis.

PATIENTS

Grating acuity and dark-adapted visual thresholds were tested in 36 patients with Leber congenital amaurosis. Longitudinal assessments were obtained for 24 patients and analyzed for significant changes over time. Visual acuity and threshold and the courses of visual acuity and threshold were examined for significant associations with hyperopia, fundus appearance, and complicated vs uncomplicated status.

RESULTS

Measurable grating acuities ranged from 0.16 to 6 cycles per degree (median, 1.27 cycles per degree or about 20/500), and dark-adapted visual thresholds were elevated 1.0 to 5.6 log units (median, 2.33 log units). Eighteen patients never had demonstrable grating acuity, and 12 had no light perception. Among those with serial tests, visual acuity improved or remained stable in 10 patients and declined in 4. Dark-adapted visual thresholds were stable in those with improving or stable visual acuities but worsened in 5 patients, including the 4 whose visual acuity worsened. No significant associations of visual acuity, dark-adapted visual threshold, the course of visual acuity, or the course of dark-adapted visual threshold with hyperopia, fundus appearance, or complicated vs uncomplicated status were found.

CONCLUSIONS

Visual capabilities varied widely. Vision was stable in the majority by longitudinal measures but increased in a few and deteriorated in others. Neither ocular characteristics nor complicated vs uncomplicated status predicted visual function. Thus, if vision and its course are to be known in a patient with Leber congenital amaurosis, it must be tested.

Photoreceptor function in infants and children with a history of mild retinopathy of prematurity

Five infants and children with a history of mild retinopathy of prematurity (ROP) were tested for postulated alterations in rod photoreceptor function. The photoreceptor responses were derived from the electroretinographic alpha waves. Postreceptoral components, the beta wave and the oscillatory potentials, were also examined. The saturated amplitude and sensitivity of the rod photoreceptor responses were low, except for the sensitivity in one patient. The beta-wave sensitivity was low, but saturated amplitudes were within the 95% prediction interval for normal. The amplitudes of the oscillatory-potential responses were also attenuated. The results indicate that retinal dysfunction may be present in patients with a history of mild ROP long after the ROP has completely resolved. Additionally, the data suggest that the photoreceptors are the primary site of retinal dysfunction in mild ROP.

Effect of prior oxygen exposure on the electroretinographic responses of infant rats

PURPOSE

To study electroretinographic responses of infant rats with a history of exposure to high-ambient oxygen.

METHODS

Electroretinographic responses to a range of full-field stimuli were recorded from 13-day-old (n = 8) and 18-day-old (n = 10) rats with a history of intermittent exposure to 80% oxygen and age-matched controls. The a-waves were fitted with a model of rod cell sensitivity and saturated response amplitude. The amplitudes and implicit times of the b-wave and oscillatory wavelets were examined as a function of stimulus energy. Response parameters in oxygen-exposed rats were compared to those in controls.

RESULTS

The amplitude of the saturated rod response was reduced in oxygen-exposed 13-day-old but not 18-day-old rats. The sensitivity of the rod response was reduced in both 13- and 18-day-old oxygen-exposed rats. The saturated amplitude and sensitivity of the b-wave did not differ significantly between oxygen-exposed and control rats age 13 days, but both amplitude and sensitivity were significantly decreased in 18-day-old oxygen-exposed rats. Oscillatory potentials, which could be investigated only in 18-day-old rats, showed significant attenuation of OP3 but not OP4 amplitudes in the oxygen-exposed rats. The sensitivity of OP2 did not differ significantly between oxygen-exposed and control rats. The avascular area in the oxygen-exposed rats was not correlated with any of the rod cell, b-wave, or oscillatory potential response parameters.

CONCLUSION

The function of the rod photoreceptors, as well as the inner retina, is altered in infant rats with a history of oxygen exposure.