CYAN EXHIBIT 1030
`
`MAY 1979 Vol. 18/5
`
`Investigative Ophthalmology
`& Visual Science
`
`A Journal of Clinical and Basic Research
`
`
`Articles
`
`Structural and biochemical changes in
`vitamin A—deficient rat retinas
`
`Louvenia Carter-Dawson, Toichiro Kuwabara, Paul]. O’Brien, and John G. Bieri*
`
`The levels of rhodopsin and opsi n were investigated in relation to the maintenance of retinal
`structure in retinas of vitamin A—deficient rats reared in low levels of cyclic illumination (1.5 to
`2 foot-candles). Rhodopsin levels decreased in the deficient retinas to approximately 20% of
`control at 9 weeks, and this level was retained through 39 weeks on the deficient diet. Opsin
`levels decreased at a slower rate but reached about 20% of control levels at 32 weeks. Despite
`the decrease in rhodopsin levels, obvious deterioration of disc structure was not observed
`until 16 weeks of deficiency, when opsin levels had already decreased to 60% to 70% of control.
`The structural disruption of photoreceptor outer segments was localized initially in discs
`of the distal
`third. Rod cell degeneration preceded cone cell degeneration in vitamin
`A—deficient retinas. Most of the rods and cones persisted in the posterior retina at 23 weeks on
`the deficient diet; however, by 40 weeks, only 11% of the rod nuclei remained. In contrast,
`about 63% of the cone nuclei were present at 40 weeks of deficiency. The photoreceptor cells
`were affected by the deficiency to a greater extent in the inferior hemisphere than in the
`superior hemisphere of the eye.
`
`Key words: vitamin A deficiency, photoreceptor degeneration, rat, rhodopsin,
`opsin, rods, cones
`
`Vitamin A deficiency has been shown to
`produce biochemical, morphological,
`and
`physiological changes in the retina. In rat ret—
`inas,
`the first sign of the deficiency, night
`
`
`
`From the Laboratory of Vision Research, National Eye
`Institute, and *National Institute of Arthritis, Metal)-
`olism and Digestive Diseases, National Institutes of
`Health, Bethesda, Md.
`Submitted for publication June 12, 1978.
`Reprint
`requests: Louvenia Carter-Dawson, Ph.D.,
`Building 6, Room 201, National Institutes of Health,
`Bethesda, Md. 20014.
`
`blindness, was determined by the rise in
`threshold for eliciting the electroretinogram
`(ERG). This rise in threshold was directly re-
`lated to a decrease in the level of rhodopsin
`detected by 4 to 5 weeks on the dietary reg-
`imen. "4 By 10 months, no response could be
`elicited from retinas of the deficient rats."2
`Structural deterioration of outer and inner
`
`segments occurred" 5‘3 as well as degenera-
`tion of photoreceptor nuclei."3’ 7’ 9
`Several studies have shown the presence of
`cone photoreceptors in the rat retina.”—l3
`Cone photoreceptor cells are affected to a
`
`437
`
`

`

`438 Carter-Dawson et (ll.
`
`Invest. Ophthalmol. Visual Sci.
`May 1979
`
`lesser extentin some experimental lesionsw’ ‘4
`and some genetic disorders in several spe-
`cies.‘5"8 The present study was designed to
`compare the rate of rod and cone degenera-
`tion and the ultrastructural deterioration of
`
`outer segments associated with decreasing
`levels of rhodopsin and opsin in vitamin
`A-deficient rat retinas.
`
`Materials and methods
`
`Animals. In order to accelerate the depletion of
`retinol from the experimental animals, pregnant
`female Sprague-Dawley rats were fed a vitamin
`A—deficient diet (basal diet*) 7 days prior to deliv-
`ery and throughout lactation. This procedure re~
`sults in ofl‘spring with normal blood levels of ret—
`inol, but with reduced liver stores and thus an
`earlier onset of tissue depletion (Bieri, unpub-
`lished observations). The male offspring were
`weaned at 21 days of age and divided into three
`groups:
`(1) basal diet,
`(2) basal diet plus retinyl
`palmitate (4 mg/kg diet) at 21 days of age, and (3)
`basal diet plus retinoic acid at 35 days ofage. The
`supplement in group 3 was delayed for 2 weeks
`after weaning to prevent the known sparing of tis-
`sue retinol by retinoic acid.“ All rats were main-
`tained at a temperature of about 24° C with 12 hr
`cyclic illumination of 1.5 to 2 foot-candles.
`Rhoclopsin and opsin measurements. Rats were
`dark-adapted overnight, and the eyes were enu-
`cleated under ether anesthesia in dim red light.
`After rinsing in physiological saline, the lens and
`vitreous were removed through a slit in the cor—
`nea. To prevent loss of retinal tissue in dissection,
`the whole eye cup from a given rat was homoge-
`nized in 1 ml of phosphate buffer (66 mM, pH
`7.1).
`rhodopsin measurement, 10 pd of the
`For
`nonionic detergent Emulphogene BC 720 (Gen-
`eral Aniline and Film) was added to each sample
`and allowed to stand for 1 hr at room temperature.
`However,
`for opsin measurements, both control
`and deficient retina homogenates were bleached
`for 10 min with 60 foot-candles of white light, and
`0.1 pmol of 9-cis-retinal was added to each
`homogenate in the dark.22 Each sample with reti-
`nal was incubated for 5 hr at room temperature
`
`*Percentage composition: vitamin-free casein, 20; DL-
`methionine, 0.3; cellulose, 5.0; corn oil, 5.0; AIN-76
`mineral mix,l9 3.5; vitamin mix-3 without retinol,20 2.0;
`sucrose, 64.2. DL-a-Tocopheryl acetate was added at
`20 mg/kg.
`
`before another 0.1 mnol 9-cis-retinal was added.
`These mixtures were incubated at 4° C overnight.
`On the following day, the samples were warmed to
`room temperature for 30 min and incubated with
`10 (11 of Emulphogene for 1 hr. All samples were
`centrifuged at 25,000 X g for 15 min to clarify the
`rhodopsin or isorhodopsin extracts. To each sam-
`ple, 0.1 ml of hydroxylamine (0.1M, pH 7.2) was
`added. A Beckman Acta II spectrophotometer was
`used to scan the absorption spectra of the extracts
`before and after exposure to white light of about 60
`foot-candles for 10 min. With the procedure de-
`scribed above for extraction of rat rhodopsin, the
`absorption peak was 493 nm as previously de—
`scribed. 23 The changes in absorbance at 493 or 485
`nm after bleaching was taken as a measure of
`rhodopsin or isorhodopsin (i.e., opsin) content, re-
`spectively. Results were expressed as percentage
`of control values. Opsin was determined by the
`above bleaching and regeneration procedure to
`provide a control, to ensure that regeneration ac-
`tually could occur and to compensate for variation
`in the degree of regeneration from one experiment
`to the other.
`
`Histological procedures. The eyes were enu-
`cleated from some rats of each group between 4
`and 40 weeks. All eyes were fixed by immersion in
`4% glutaraldehyde in 0.15M Na-K phosphate buf-
`fer at room temperature for about 80 min. Portions
`of the posterior eye cup,
`including the retina,
`were excised from the inferior hemisphere within
`2 mm of the optic nerve head. In the peripheral
`region of the same hemisphere, segments approx-
`imately 2 mm in length were excised. These seg—
`ments were postfixed with 1% osmium in the
`Na—K phosphate buH‘er for 30 min at room tem—
`perature and 30 to 45 min at 4° C. The tissue was
`processed for embedding in Epon. For light ini-
`croscopy, sections were cut at 1 to 1.5 pm and
`stained with a solution of 1% toluidine blue in 1%
`tetraborate buffer. Ultrathin sections, stained with
`uranyl acetate and lead citrate, were examined
`with an electron microscope.
`Counts of rod and cone nuclei were made in the
`
`posterior and peripheral retina of the inferior
`hemisphere. Rod and cone nuclei were distin-
`guished by their nuclear morphology. Cone nuclei
`contain multiple small clumps of heterochromatin,
`and rod nuclei contain a large central clump. ‘0' “‘ ”
`In the posterior and peripheral regions, seven
`consecutive segments 90 pm in length were exam-
`ined in each of four sections. Counts were made
`
`within 2 mm of the optic nerve head in the
`posterior retina and beginning 180 pan from the
`ora serrata moving posteriorly in the peripheral
`
`

`

`Volu me 18
`Number 5
`
`Vitamin A—(leficie-nt rat retinas
`
`439
`
`
`
`
`
`
`Weigh!ingrams
`
`0
`
`2
`
`4
`
`6
`
`8
`
`IO
`
`12
`
`14
`
`o—c Basal diet 4‘ vetinyl pulmitale
`o—o Basal diet 0 retinoic add
`I—- Basal diet
`
`22
`
`24
`
`26
`
`2E
`
`30
`
`32
`
`,1
`
`20
`IO
`6
`Week: an die!
`
`Fig. 1. Weight of rats on basal diet, basal diet + retinoic acid, and basal diet + retinyl
`palmitate. Each point represents the mean weight of 4 to 8 animals.
`
`retina. The numbers of rod and cone nuclei were
`
`first 2 weeks of the diet. Around the third
`
`recorded in each region, and the mean, standard
`error of the mean, and percentage of remaining
`rod and cone nuclei were calculated.
`To compare the elTects of the deficiency on the
`four quadrants of retina, eyes from two rats sup-
`plemented with retinoic acid were examined at 36
`weeks on the diet. The left eyes were bisected
`through the optic nerve along the vertical merid-
`ian and the right eyes along the horizontal merid-
`ian after fixation in glutaraldehyde. Portions of the
`cornea were removed to indicate inferior and nasal
`hemispheres. The half hemispheres were post-
`fixed and embedded in Epon as described above.
`Sections were cut to include the cornea; thus, in a
`given section,
`temporal and nasal regions or in-
`ferior and superior regions were present. Seven
`consecutive segments, 90 am in length, were ex—
`amined in each of four sections beginning 180 pm
`from the era serrata moving posteriorly. The
`number of photoreceptor cells was recorded for
`each region, and the mean and standard error of
`the mean were calculated.
`
`Results
`
`three groups
`in all
`Animals. Animals
`gained weight at about the same rate for the
`
`week, rats in the group receiving only the
`basal diet weighed approximately 20 gm less
`than those supplemented with retinoic acid
`or retinyl palmitate. Rats fed only the basal
`diet also showed porphyrin around their
`eyes. By 4 weeks, many animals lost weight
`(Fig. I), became lethargic, and showed hind
`limb weakness. All rats in this group were
`sacrificed by the fifth week. Rats in the other
`two groups continued to gain weight. Those
`supplemented with retinoic acid did not gain
`as much as the ones supplemented with ret-
`inyl palmitate (control group) beginning at 8
`weeks on the diet through the period stud—
`ied. These differences in weight were not
`statistically significant (mean i- S.D.: plus
`retinoic acid 481 t 47 gm; plus retinyl pal-
`mitate, 521 i 53; p > 0.2). Rats maintained
`with retinoic acid appeared as healthy as
`those supplemented with retinyl palmitate.
`Rhodopsin and opsin levels. The amount of
`rhodopsin in the retinas of vitamin A-
`deficient rats (plus retinoic acid) was below
`control levels as early as 2 weeks on the diet
`
`

`

`440 Carter-Dawson et al.
`
`Invest. Ophthalmol. Visual Sci.
`May 1979
`
`
`
`.
`
`Pusan!olccnlvol
`
`‘
`
`o—o Rhodopsin
`r—u Opsin
`
`
`
`o
`
`2
`
`4 e-é ioiziti61'82'02'2'1'42'62'3503'2543'63840
`Wulu on diet
`
`Fig. 2. Rhodopsin and opsin levels in vitamin A—deficient retinas expressed as percent of
`control. The curves are drawn to show the general trend of rhodopsin and opsin levels.
`
`(Fig. 2). The level of rhodopsin was about
`70% of the normal value at 2 weeks. Over the
`
`the percentage of rho-
`following 8 weeks,
`dopsin decreased to approximately 20% of
`control values. (Analyses were made only on
`eyes from rats supplemented with retinoic
`acid, since those on the basal diet were sac-
`rificed by 5 weeks. Hereafter, rats referred to
`as deficient were fed the basal diet plus ret-
`inoic acid.) The amount of rhodopsin in the
`retinas of the deficient rats remained rela-
`tively constant between 10 and 39 weeks on
`the diet. Opsin levels remained high in the
`retina during the early stages of vitamin A
`deficiency. After 8 weeks on the deficient
`diet, the retinas contained 85% of the control
`value ofopsin (Fig. 2). By 28 weeks, the level
`of opsin was around 40% of control. The per-
`centage of opsin dropped to 19% of control
`levels by 32 weeks of deficiency.
`Histology. Retinas of rats in all groups ap—
`peared normal through 5 weeks on their re-
`spective diets. By 7 weeks,
`the distal
`two
`thirds of the outer segments in the posterior
`retina of rats supplemented with retinoic acid
`stained less intensely with toluidine blue, but
`no other morphological changes were seen.
`
`However, around 16 weeks on this diet, the
`outer segments began to show morphological
`abnormalities. Some discs were distended
`
`and disrupted into small vesicles ranging
`from 0.19 to 0.35 pan in diameter. This ab-
`normal structure was confined largely to the
`distal third of the outer segment. The length
`of these outer segments in the posterior ret-
`ina of rats receiving retinoic acid was compa-
`rable to controls (mean i S.E.M.: plus ret-
`inoic acid, 21 i 0.4 pm; control, 20 i- 0.3;
`n = 10 outer segments).
`At 23 weeks,
`the structure of outer seg-
`ments in the posterior region of deficient rat
`retinas appeared more disorganized (Fig. 3).
`Many discs in the distal third of the outer
`segments were distended or dispersed into
`vesicles approximately 0.1 to 0.3 am in di—
`ameter. Some outer segment discs were ori-
`ented parallel
`to the long axis. Numerous
`densely stained, membranous vesicles, 0.2 to
`0.4 pm in diameter, presumably portions of
`disc membranes, were present in the pig—
`ment epithelium and between pigment epi-
`thelial cell processes. In contrast, discs in the
`outer segments of refinas from rats sup-
`plemented with retinyl palmitate (control
`
`

`

`Valium.- [8
`Number 5
`
`Vitamin A—deficient rut retinas
`
`441
`
`
`
`Fig. 3. Posterior retina of vitamin A—deficient nit maintained on the diet 23 weeks. The discs
`in the distal portion of many outer segments are disrupted into small vesicles. Some small
`vesicles are present between and in pigment epithelial processes (arrow). Processes of the
`pigment epithelium (pep) have lost their normal contact with outer segments.
`
`group) were intact (Fig. 4). The outer seg~
`ments were also shorter by 5 um at 28 weeks
`in the posterior retina (mean i S.E.M.-. de-
`ficient,
`l4 1' 0.3 pm; control,
`19 t 0.1;
`n = 10 outer segments).
`The intimate contact between the pigment
`
`epithelial cells and outer segments was lost
`in light-adapted deficient rat retinas (Fig. 3).
`Also, the lipid droplets in the pigment epi-
`thelium of the deficient retinas were quite
`homogeneous
`in density, except
`for
`an
`electron-dense cortical region (Fig. 5). Most
`
`

`

`442 Carter-Dawson et (:1.
`
`insert. Ophllmlmul. Visual Sci.
`May 1979
`
`
`
`Fig. 4. Outer segment tips in the posterior region of the control retina maintain contact with
`pigment epithelial processes (pep). The outer segment discs also maintain their normal struc-
`ture (28 weeks on diet).
`
`of the lipid droplets were located near the
`base of the pigment epithelial cells. The
`density and size of these droplets varied from
`cell to cell. The distribution and density of
`other organelles in the pigment epithelial
`cells appeared normal. In contrast, the pig-
`ment epithelial processes of the control
`animals were closely apposed to the outer
`segments. and the lipid droplets were less
`homogeneous in density. Several concentric
`rings were seen in the lipid droplets, which
`varied in electron density. In the center of
`these droplets electron-lucent spots were
`often seen (Fig. 6). The distribution and
`number of lipid droplets 1.5 pm in diameter
`and larger were similar in the control and
`deficient epithelial cells.
`Degeneration of both rod and cone nuclei
`
`was seen in the posterior retina of vitamin
`A—deficient rats. Most of the rod nuclei per.
`sister] through 23 weeks of deficiency (Table
`I). By 28 weeks on the diet about 59% re-
`mained. Twelve weeks later, at 40 weeks,
`only about 11% of the rod nuclei survived.
`Less than 13 rods/90 pan length persisted in
`the posterior retina of deficient rats at 40
`weeks (Table I). Some cone nuclei also de-
`generated as early as rods. However,
`the
`percentage of surviving cone nuclei was
`greater than that of rod nuclei at 28 weeks.
`By 40 weeks of deficiency, approximately
`62% of the cone nuclei persisted in the
`posterior retina, whereas only about 11% of
`the rod nuclei remained (Table 1, Figs. 7
`and 8).
`Rod and cone nuclei survived longer in the
`
`

`

`Volume 18
`Number 5
`
`Vitamin A-deficient mt retinas
`
`443
`
`
`
`Fig. 5. Typical lipid droplet in the pigment epithelium of a vitamin A—deficient retina.
`Fig. 6. Lipid droplet in pigment epithelium ofcontrol retina. Electron-lucent spots are promi-
`nent in the internal structure.
`
`Table 1. Rod and cone nuclei" in sections of retinas from control and vitamin A—deficient rats
`
`l D
`
`eficient l
`
`94.5 t 2 I
`1.5 t 0.1
`85.6
`93.8
`
`65.0 .+_ 2 6
`1.4 t 0.3
`58.9
`87.3
`
`12.5 + 0.5
`1.0 : 0.1
`11.3
`62.5
`
`Conn-01,1
`28 wk
`
`110.4 I 0.5
`1.6 = 0.2
`
`96.
`
`8
`2
`
`
`
`Weeks on diet:
`
`Posterior retina:
`Hod nuclei
`Cone nuclei
`% rod nuclei renmining
`% cone nuclei remaining
`Peripheral retina;
`Hod nuclei
`Cone nuclei
`96 rod nuclei remaining
`95 cone nuclei remaining
`
`60.0
`[.0
`
`It'4’
`
`1.0
`0.2
`
`54.4 t 1.1
`1.0 t 0.2
`90.7
`100
`
`53.2: 11
`1.0 1 0.2
`88.7
`100
`
`17.5 1 1.0
`0.7 t 0.2
`29
`70
`
`‘ Mean 3 S. EM. per 90 Jun length of retina: count: based on 28.90 urn lengths. 7 consecutive lengths in each 01"! sections.
`lCun'trol. lrasal that + letlnyl palmitate.
`l Deficient. basal diet + retinoic acid.
`
`peripheral retina than in the posterior retina.
`At 28 weeks of deficiency, about 59% of the
`rod nuclei persisted in the posterior retina,
`but approximately 89% remained in the pe-
`ripheral retina. By 40 weeks, about 11% and
`29% survived in the posterior and peripheral
`retinas, respectively (Table 1). Cone nuclei of
`the deficient retinas also survived longer in
`the peripheral retina than in the posterior
`retina. The number of cone nuclei was not
`
`affected in the peripheral retina at 23 or 28
`weeks, but some cone nuclei had degener-
`ated in the posterior retina (Table I).
`
`All hemispheres of the retina in vitamin
`A~deficient rats were not affected to the
`same extent. At 36 weeks on the deficient
`
`diet (plus retinoic acid) peripheral temporal
`and nasal retinas contained 20.3 1' 2.2 and
`
`25.5 1 3.2 photoreceptor cells/90 um re-
`spectively (mean i S.E.M.; p > 0.2). In the
`periphery, 32.1 I 0.9 photoreceptor cells/90
`you were seen in the superior hemisphere,
`but only 18.2 i 1.9 were seen in the inferior
`hemisphere (mean : S.E.M.: control, su-
`perior
`hemisphere
`61.1 i 1.6;
`inferior
`hemisphere 61.1 i 2.0; p <01). Photore-
`
`

`

`444 Carter-Dawson et at.
`
`Invest. Ophthalmol. Visual Sci.
`Mnll [979
`
`
`
`Fig. 7. Outer nuclear layer of a 10-month control retina. Cone nuclei (arrows) are present
`among many rod nuclei.
`Fig. 8. One to two rows ofphotoreceptor nuclei remain in deficient retinas, as well as remnants
`ofiuuer and outer segments. Cone nuclei are distinguished by their nuclear chromatin pattern
`(arrow).
`
`ceptor cells were affected to a greater extent
`in the inferior half of the eye.
`
`Discussion
`
`We observed dilterences in the rate of loss
`
`of rhodopsin, opsin, and photoreceptor nu-
`clei at various stages of vitamin A deficiency.
`Rhodopsin levels decreased 1 to 5 weeks ear-
`lier than reported previously.""" 7 Although
`rhodopsin levels decreased below 30% of
`normal at 8 weeks, opsin levels were 85% of
`normal. At 8 weeks ot'deficiency the amount
`of opsin found in the present study was
`greater than reported previously by 24%.
`Even at 32 weeks ofdeficiency 20% ofnormal
`rhodopsin and 19% of regenerable opsin
`persisted. Perhaps the difi'erences observed
`between our results and those of previous
`studies are a result of a difference in rat
`
`strain, type of diet. or level of illumination.
`Structural deterioration of photoreceptor
`Outer segments initiated at their distal tips
`and progressed proximally in vitamin A—
`deficient
`retinas. Why degeneration pro-
`ceeded in this fashion is unclear, but at least
`two possibilities can be invoked to explain
`the observed pattern. First, the available vi-
`tamin A may be bound preferentially to
`newly synthesized membranes at the base of
`the outer segment, and in the absence ol'ret-
`inol, opsin may undergo denaturation, result-
`ing in structural deterioration. Second, disc
`synthesis may be slowed“; thus discs which
`
`are normally shed remain attached for longer
`periods and then deteriorate as a function of
`their age.
`The pigment epithelium of the vitamin
`A—deficient rats remained structually normal
`except for the ultrastmcture of the lipid drop-
`lets. Many of the lipid droplets in the
`deficient pigment epithelium were quite
`homogeneous in structure. However,
`those
`in the control pigment epithelium were less
`homogeneous and ofien contained electron-
`lucent spots. These droplets were similar in
`structure to those described by Robison and
`Kuwabara’5 in the pigment epithelium of
`mice receiving injections of vitamin A. Al-
`though these lipid droplets do show various
`forms of electron density,“ the preponder-
`ance of the more homogeneous type ob-
`served in the deficient pigment epithelium
`suggests a (liEerence in composition. This dif-
`ference may be related to low levels or ab-
`sence of stored vitamin A or its metabolites.
`
`The most striking change seen in the vi-
`tamin A—deficient retinas was the differential
`
`rate of rod and cone cell degeneration. Ap-
`proximately 12% of the rod nuclei had cle-
`generatcd in the posterior
`retina by 23
`weeks, whereas only abOut 6% of the cones
`were lost. By 40 weeks, 89% ol'd'ie rod nuclei
`had degenerated but only 37% of the cone
`nuclei. Rod cells may degenerate faster than
`cones because of metabolic differences.
`
`Rod photoreceptor cells were affected
`
`

`

`Volume 18
`Nu mber 5
`
`Vitamin A—deficient rat retinas
`
`445
`
`more than cones in human patients with ab—
`normally low serum levels of vitamin AZ6
`Patients with abetalipoproteinemia have low
`serum levels of vitamin A. Electrophysiologi-
`cal studies showed a reduction in amplitude
`of the ERC, but a small signal could be iso-
`lated exclusively from cones. By 6 hr after
`administration of vitamin A, the amplitude of
`the ERG for cones was increased, but that of
`rods increased only after 24 hr. Histopatho-
`logical examination of the retina from a pa-
`tient with abetalipoproteinemia revealed com-
`plete degeneration of the photoreceptor cells
`except in the macula and the area between
`the macula and temporal margin of the disc.
`Cones were seen in both regions, and a small
`number of rods were seen in the tempo-
`ral margin of the discs.27 The rods appear to
`be affected to a greater extent than cones.
`Whether or not these changes are due pri—
`marily to the low levels of vitamin A in these
`patients is unknown.
`Regional differences were seen in the rate
`of photoreceptor cell degeneration in the
`present study. The percentage of photore-
`ceptor cells remaining in the posterior retina
`was lower than that seen in the peripheral
`retina at 28 weeks of deficiency and persisted
`through 40 weeks. Thus a central-peripheral
`gradient of photoreceptor cell degeneration
`exists. This central-peripheral gradient of de—
`generation has been observed in other retinal
`lesions.‘8' 23
`
`Another regional ditference in degenera-
`tion was seen in retinal hemispheres. More
`photoreceptor cells were seen in the periph-
`ery of the superior hemisphere than in the
`periphery of the inferior hemisphere. Photo-
`receptor cells degenerated faster in the in-
`ferior region of the eye.
`The photoreceptor cells in the inferior re—
`gion of the retina are affected to a greater
`extent in some experimental and genetic le-
`sions. Iodoacetate poisoning produces more
`damage to photoreceptor cells in the inferior
`hemisphere of cats and rabbits.28 Sector ret-
`initis pigmentosa in man frequently pro—
`duces more damage in the inferior nasal half
`of the eye.29 Photoreceptor cells in the in-
`ferior hemisphere of black-eyed Royal Col-
`
`lege of Surgeons (RCS) rats and dark-reared
`pink-eyed RCS are more severely affected.23
`However, the peripheral retinas of pink-eyed
`RCS rats reared in cyclic light, 20 to 35 foot-
`candles, show uniform degeneration in the
`superior and inferior hemispheres.23 Light
`appears to accelerate the rate of degeneration
`in the superior region of the eye in the pink-
`eyed RCS rats.
`It is unclear whether the rate of photore-
`ceptor cell degeneration in the superior
`hemisphere was affected by illumination in
`the present study. The rats used in our study
`were reared in dim cyclic light (maximum of
`1.5 to 2 foot-candles). Perhaps this level of
`illumination can produce the same effects in
`the superior hemisphere of vitamin A—
`deficient retinas as darkness does in the
`
`retinas of pink-eyed RCS rats. It is also a
`possibility that regional differences in retinal
`hemispheres occur in vitamin A—deficient
`retinas independently of the lighting condi-
`tion. Additional studies are needed to deter-
`
`mine whether regional degeneration is me-
`diated by light.
`We thank Ms. Teresa Tolliver and Mr. William
`Mills for technical assistance. Special
`thanks are ex-
`tended to Mr. Leonard L. Dawson for preparing the
`graphs.
`
`REFERENCES
`
`1. Dowling, ].E., and Wald, 0.: Vitamin A deficiency
`and night blindness, Proc. Natl. Acad. Sci. U. S. A.
`44:648, 1958.
`2. Dowling, ].E., and Wald, C.: The biological func-
`tion ofvitamin A acid, Proc. Natl. Acad. Sci. U. S. A.
`46587, 1960.
`].N., Pitt, C.A., and
`3. Lewin, D.R., Thompson,
`Howell, ].M.: Blindness resulting from vitamin A
`deficiency in albino and pigmented guinea pigs and
`rats, Int. J. Vitam. Res. 40:270, 1970.
`4. Noell, W.K., Delmelle, M.C., and Albrecht, R.:
`Vitamin A deficiency effect on retina: dependence of
`light, Science 172:72, 1971.
`5. Tansley, K.: Factors affecting the development and
`regeneration of visual purple in the mammalian ret-
`ina, Proc. R. Soc. B 114:79, 1933.
`6. Johnson, M.L.: The effects of vitamin A deficiency
`upon the retina ofthe rat, J. Exp. Zool. 81:67, 1939.
`7. Dowling, ].E., and Gibbons, 1.11.: The effect of vi—
`tamin A deficiency on the fine structure of the ret-
`ina. In Smelser, 0., editor: The Structure of the
`Eye, New York,
`1961, Academic Press,
`Inc.,
`1). 85-99.
`
`

`

`446 Carter-Dawson at a].
`
`Invest. Ophthalmol. Visual Sci.
`May 1979
`
`Hayes, K.C.: Retinal degeneration in monkeys in-
`duced by deficiencies of vitamin E or A,
`INVEST.
`OPHTHALMOL. 13:499, 1974.
`Ramalingaswami, V., Leach, E.H., and Srirama-
`chari, 5.: Ocular structure in vitamin A deficiency in
`the monkey, Q. ]. Exp. Physio]. 40:337, 1955.
`Walls, C.L.: The visual cells of the white rat, J.
`Comp. Psychol. 18:363, 1934.
`Soko], 5.: Cortical and retinal spectral sensitivity of
`the hooded rat, Vision Res. 10:253, 1970.
`Green, D.C.: Scotopic and photopic components of
`the rat electroretinogmm, J. Physio]. 228:781, 1973.
`Cicerone, C.: Cones survive rods in the light-
`damaged eye of the albino rat, Science 194:1183,
`1976.
`LaVai], M.M.: Survival of some photoreceptor cells
`in albino rats following long-term exposure to con-
`tinuous light, INVEST. OPIITHALMOL. 15:64, 1976.
`Parry, H.B.: Degenerations of the dog retina.
`II.
`Generalized progressive atrophy of hereditary ori-
`gin, Br. J. Ophthalmol. 37:487, 1953.
`Aguirre, C.D., and Rubin, L.F.: Progressive retinal
`atrophy (rod dysplasia) in the Norwegian elkhound,
`J. Am. Vet. Med. Assoc. 158:208, 1971.
`Aguirre, C. D., and Rubin, L.F.: Rod—cone dysplasia
`(progressive retinal atrophy) in Irish Setters, J. Am.
`Vet. Med. ASSOC. 166:157, 1975.
`Carter-Dawson, L.D., LaVai], M.M., and Sidman,
`R.L.: Differential effect of the rd mutation on rods
`and cones in the mouse retina,
`INVEST. OPHTHAL-
`MOL. VISUAL SCI. 17:489, 1978.
`Report of the American Institute of Nutrition Ad
`Hoc Committee on Standards for Nutritional Stud-
`ies, J. Nutr. 7:1340, 1977.
`
`10.
`
`11.
`
`12.
`
`13.
`
`14.
`
`15.
`
`16.
`
`17.
`
`18.
`
`19.
`
`20.
`
`21.
`
`22.
`
`23.
`
`24.
`
`25.
`
`26.
`
`27.
`
`29.
`
`Bieri, ].C., and Priva], E.L.: Effect ofdeficiencies of
`a-tocopherol, retino] and zinc on the lipid composi-
`tion of rat testes, J. Nutr. 89:55, 1966.
`Krishnamurthy, 5., Bieri, ].C., and Andrews, E.L.:
`Metabolism and biological activity of vitamin A acid
`in the chick, J. Nutr. 79:503, 1963.
`O’Brien, P.]., and Muellenberg, C.C.: The biosyn-
`thesis of rhodopsin in vitro, Exp. Eye Res. 18:241,
`1974.
`LaVail, M.M., and Battelle, B.A.; Influence of eye
`pigmentation and light deprivation on inherited ret-
`ina] dystrophy in the rat, Exp. Eye Res. 21:167,
`.1975.
`Herron, W.K., ]r., and Riege], B.W.: Production
`rate and removal of rod outer segment material in
`vitamin A deficiency,
`INVEST. Ol’l-lTl-IALMOL. 13:46,
`1974.
`Robison, W.C., 11"., and Kuwabara, T.: Vitamin A
`storage and peroxisomes in retinal pigment epithe-
`lium and liver,
`INVEST. OPllTl-lALa-IOL. VISUAL SCI.
`1611110, 1977.
`Coums, P., Carr, RE, and Gunkel, R.D.: Retiuitis
`pigmentosa in abeta]ipoproteinemia: effects of vi-
`tamin A, INVEST.OPHTHALMOL. 10:784, 1971.
`Von Sallmann, L., Gelderman, AH, and Laster,
`L.; Ocular histopathologic changes in a case of
`A-Beta-Lipoproteinemia, Doc. Ophthalmol. 26:451,
`1969.
`Noel], W. K. : The impairment ofvisua] cell structure
`by iodoacetate, J. Cell Comp. Physiol. 40:25, 1952.
`Krill, A.E., Archer, D., and Martin, D.: Sector ret-
`initis pigmentosa, Am. J. Ophthalmol. 69:977, 1970.
`
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