effects of repeated microwave irradiations to the albino rabbit eye

Effects of repeated microwave irradiationsto the albino rabbit eye

S. E. Hindi," Maj MC, USA, B. Appleton,* Col MC, USA,B. S. Fine,** and P. V. K. Brown***

Albino rabbits were exposed to repeated microwave irradiations once daily for a month.Clinical examination was carried out for a period up to one year. No changes occurredbelow 300 rriW./cm.2, At and above this level posterior subcapsular iridescence and posteriorcortical cataracts were produced. The histologic findings in posterior subcapsular iridescenceare presented. It appears that the nonprogressive posterior cortical cataracts are a result ofthe temperature levels generated by the microwaves in the immediate retrolental area.

Key words: microwave, rabbit, cataract.

From the "Department of Ophthalmology, WalterReed General Hospital, * "Ophthalmic PathologyDivision, Armed Forces Institute of Pathology,and ,""" Department of Microwave Research,Walter Reed Army Institute of Research, Wash-ington, D. C.

Supported in part by Research Grant No. FD-00686 from the Food and Drug Administration,Department of Health, Education and Welfare(Dr. Fine).

In conducting the research described in this report,the investigators adhered to the "Guide forLaboratory Animal Facilities and Care," aspromulgated by the Committee on the Guidefor Laboratory Animal Facilities and Care ofthe Institute of Laboratory Animal Resources,National Academy of Sciences-National ResearchCouncil.

The opinions or assertions contained herein arethe private views of the authors and are not tobe construed as official or as reflecting the viewsof the Department of the Army or the De-partment of Defense.

Reprint requests: Maj. S. E. Hirsch, MC, Ophthal-mic Pathology Division, Armed Forces Instituteof Pathology, Washington, D. C.

s./ince the late 1940's and early 1950'smuch concern for the ocular effects ofmicrowave irradiation has been present.With the introduction of multiple-frequen-cy, high-energy microwave-generatingequipment, continued interest and contro-versy have precipitated renewed investiga-tions into the potential problems of acci-dental injury. The cataractogenic propertiesof microwave irradiations are controversial.Our previous report' on the effects ofsingle exposures to irradiations of increas-ing power density given to albino rabbits,with follow-up for periods of 1 year duringwhich development of cataracts was notobserved, served as the basis for the presentexperiment.

Materials and methods

Adult New Zealand albino rabbits of approxi-mately similar size and weight were used forthis experiment. All eyes were examined withthe ophthalmoscope and slit lamp, fully dilated,prior to irradiation in order to detect any pre-

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316 Hirsch et al. est. Ovhthalmot. Visual Sci.April 1977

Table I. Exposures

Fig. 1. Slit lamp photograph showing upper andlower halves of posterior cortical cataract. (FromYanoff, M., and Fine, B. S.: Ocular Pathology.A Text and Atlas, Hagerstown, Md., 1975, Harper& Row, Publishers.)

Fig. 2. Gross photograph of posterior corticalcataract seen in Fig. 1. The photograph is takenfrom behind after the eye was opened. (FromYanoff, M., and Fine, B. S.: Ocular Pathology.A Text and Atlas, Hagerstown, Md., 1975, Harper& Row, Publishers.)

existing comeal or lenticular abnormalities. Allmaterials and methods, equipment, and exposuretechniques were identical with those describedin our previously published report.1 The fre-quency of irradiation was 3,000 MHz.

Exposures were given to the left eye of eachanimal for a 15 minute period each consecutiveday for a total of 30 days (for those whichsurvived the 30 day period). The power densitiesof irradiation used were 50, 100, 200, 300, 400,and 500 mW./cm.2.

Clinical examination by slit lamp was carriedout daily for the first 30 days and intermittentlythereafter for up to 1 year.

Powerdensity

ImW./cm2)for 15'

exposure

50100200300400500

Originalanimals

55555

10

A nimalssurviving

30 exposures

544413

Averageexposuresreceived

by animalthai died

222318g4

Table II. Responses

Power density(mWJcm2)

for 15' exposure

50100200300

400

500

Acute changes

NoneNoneNoneAll developed

iritis

Chronic changes

NoneNoneNonePSI al avg.

17'/2daysPSI at avg. 10 days;

opacities at avg.15 days

PSI at avg. 5 days;vacuoles at avg.8 days; opacitiesat avg. 10 days

Selected animals were sacrificed for histologicstudy by both light and electron microscopy.

Results

The exposures and responses of the ani-mals are listed in Tables I and II, re-spectively.

As the power density increased, fewer ofthe animals survived the 30 day irradiation.The reasons for the deaths were not de-termined.

Below 300 mW./cm.2 no ocular changeswere detected. At 300 mW./cm.2 andabove, all eyes reacted with congestion ofthe limbal vessels, pupillary constriction,and evidence of iritis. Posterior subcapsulariridescence (PSI) developed at an averageof 17 Vz days after irradiation at the 300mW./cm.2 level. At 400 mW./cm.2 the PSIappeared at an average of 5 days, vacu-oles in the posterior cortex of the lens atan average of 8 days, and posterior corticalcataractous changes at an average of 10days.


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Effects of microwave irradiations 317

Fig. 3. Electron micrograph showing transition from relatively normal cortical lens cells(above right) to the disrupted, globular lens cells characteristic of cataractous change4 (lowerleft). (xl5,400.)

The lenticular opacities progressed butwere limited to the posterior cortex (Figs.1 to 3) during the following year ofobservation. No other ocular changes werenoted by our methods of examination.

Discussion

It is clear from these results that pro-duction of lenticular changes is dependenton the power density of the exposure. Nochanges were produced below 300 mW./cm.2 for 15 minutes/day for 30 days. Pos-terior subcapsular changes and subsequentposterior cortical opacities appeared withall power levels above 300 mW./cm.2 for15 minutes/day and much earlier at higherpower levels. It is of interest that histo-logic examination (light and electron micro-scopic) of PS I (Figs. 4 and 5) revealeda vacuolar separation from the posteriorcapsule of the most posterior cortical lenscells. Similar changes were noted near theposterior pole of the lens. The iridescence,or play of colors, therefore may be due to

Fig. 4. Slit-lamp photograph showing posteriorsubcapsular iridescence (PSI).

the thin layer of optical variations producedby this thin film of vacuoles.

Temperature measurements by Kramarand associates- have shown that maximumtemperature elevations occur in the retro-lental area adjacent to the posterior surfaceof the lens, suggesting that the changesoccurring in the adjacent deep lens cortexare the result of heat generated in theimmediate vicinity. Similar observationshave been made for the anterior lens sur-


318 Hirsch et al. Invest. Ophthalmol. Visual Sci.April 1977

Fig. 5. Inset shows zone of vacuolation between posteriormost cortical cells and posteriorlens capsule (the latter not well reproduced here). (Paraphenylenediamine; x300; AFIP Neg.No. 73-2201.) The large figure is an electron micrograph of the same material showing vacuo-lation between adjacent cortical cells (arrow) as well as between posteriormost corticalcells and posterior lens capsule (PC). (xl8,200.)

face with the use of intense incoherentwhite or infrared light.-'

Anterior subcapsular cortical lens opaci-ties can be produced where intense whitelight is absorbed by the pigment epitheliumof the iris and there converted to heat.Similar anterior lens opacities are extreme-ly difficult to produce in the albino, wherethe iris neuroepithelial layer is not pig-mented, or in the pigmented rabbit in theregions where the iris pigment epitheliumdoes not make contact with the lens.

It appears therefore that the cataractouschanges are dependent on the productionof local elevations of temperature sufficient

to injure the lens cortical cells, which be-cause of their relative inability to dissipatethe heat, undergo, first, reactive changes(intercellular vacuolation) and subsequent-ly necrotic changes (cataractous).

REFERENCES1. Appleton, B., Hirsch, S. E., and Brown, P.

V. K.: Investigation of single exposure micro-wave ocular effects at 3,000 MHz, Ann. N. Y.Acad. Sci. 247: 125, 1975.

2. Kramar, B., Emery, A. F., Guy, A. W., et al.:Theoretical and experimental studies of micro-wave induced cataracts in rabbits. In Proceed-ings of the IEEE-G-MTT International Micro-


Volume 16Number 4

Scrapie agent in hamsters 319

wave Symposium, Boulder, Colo., 1973, pp.265-267.

3. Langley, R. K., Mortimer, C. B., and McCul-loch, C : The experimental production of cata-racts by exposure to heat and light, Arch.Ophthalmol. 63: 473, 1960.

4. Yanoff, M., and Fine, B. S.: Ocular Pathology.A Text and Atlas, Hagerstown, Md., 1975,Harper & Row, Publishers, pp. 167, 372.

Ocular effects of scrapie agent in hamsters:preliminary observations

IV. Buyukmihci, R. F. Marsh, D. M. Albert, and K. Zelinski

Scrapie is caused by one of a group of so-called slow viruses responsible for the subacutespongiform encephalopathies. In the present study, young hamsters were inoculated intra-cerebrally with hamster-adapted scrapie agent. At termination, all inoculated animals showedsigns and central nervous system pathology compatihle with scrapie infection. The eyes ap-peared well developed grossly, but histologically the retina and optic nerve were abnormal-There were varying degrees of thinning of the retina, with the photoreceptor layer beingmost severely affected. Although the ganglion cell layer was not much different from thecontrols, the optic nerve appeared more cellular than that of the controls.

Key words: hamster, scrapie, retina, optic nerve, degeneration.

s,fcrapie is a transmissible disease ofsheep and goats caused by a viruslike agentand characterized by a nonfebrile, chronic

From the University of Tennessee, College ofVeterinary Medicine, Knoxville (Buyukmihci);University of Wisconsin, Department of Veteri-nary Science, Madison, (Marsh); and Massa-chusetts Eye and Ear Infirmary, Boston (Albertand Zelinski).

This project was supported in part by PublicHealth Service grant AI 11250-04 (Marsh).

Reprint requests: Ned Buyukmihci, V.M.D., Col-lege of Veterinary Medicine, University ofTennessee, Knoxville, Tenn. 37901.

course ending in complete debilitation anddeath. Clinical signs include behavioralchanges, generalized pruritus, impairmentof locomotion, and terminal anorexia.1

Scrapie has an incubation period of severalmonths to several years and thus is classi-fied as a slow virus disease. Four slow virusdiseases have such similarity that they havebeen further subdivided into a groupknown as the subacute spongiform en-cephalopathiesa with scrapie as the proto-type. The other diseases in this group in-clude kuru (a disease of New Guineanatives), transmissible mink encephalopa-thy (TME), and Creutzfeldt-Jakob disease


effects of repeated microwave irradiations to the albino rabbit eye

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