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ANIMAL RESPONSE TO LIGHT

by John M. Ott, taken from his book, Health and Light

All of my research, plus external information that came to me from many sources seemed to indicate, more and more, that animals respond to the intensity, periodicity and wavelength distribution of light in much the same way that plants do. Certainly there was sufficient additional evidence to warrant submitting another grant application to the National Institutes of Health. Several doctors prominent in research work wrote letters of recommendation to Dr. James Shannon, Director of The Public Health Service of The National Institutes of Health, resulting in his taking a personal interest in our effort and offering some guidelines to follow in submitting the next grant application. Six of the doctors, including several members of our Board of Directors, agreed to act as collaborators and actively participate in the project. They all helped in preparing the forms for the application.

The six doctors included Robert Alexander, M.D., Chief Pathologist, Presbyterian St. Luke's Hospital, Chicago; Samuel Lee Gabby, M.D., Senior Member of the staff and member of the research committee, Sherman Hospital, Elgin, Illinois; Elliot B. Hague, ophthalmologist and Chairman of the New York Academy of Sciences Conference on "Photo-Neuro-Endocrine Effects in Circadian Systems with Particular Reference to the Eye;" living H. Leopold, M.D., ophthalmologist, Director of Wills Eye Hospital, Philadelphia: Frank J. Orland, D.D.S., Director of the Walter G. Zoller Memorial Dental Clinic, of the University of Chicago, where we had previously assisted with an experiment that showed a relationship between the amount of tooth decay and the type of light environment that laboratory animals were kept under (mentioned in Annals of Dentistry, Vol. XXVII, No. 1, March 1968, Page II), and Edward F. Scanlon, M.D., member of the staff and Head of the Tumor Research Committee of the Evan-ston Hospital in Evanston, Illinois.

Meanwhile, I was invited to speak before the Sarasota County Medical Society and show the time-lapse pictures. Shortly thereafter, Dr. Thomas G. Dickinson, who had originally put me in touch with the Wills Eye Hospital, held a special meeting at his home and invited other doctors who had indicated their interest in our light experiments. One of the doctors was Roscoe Spencer, M.D., who had recently retired as Medical Director of the United States Public Health Service, where he had been in charge of cancer research. He wrote a strong letter of recommendation to the new Director of the National Cancer Institute, Dr. Kenneth M. Endicott, urging that favorable consideration be given to our currently pending grant application. A month later a letter advised us that the National Advisory General Medical Sciences Council did not recommend approval of our application. Upon our request for specific reasons, we were informed as follows:

Chalk up one more disappointment and a big one this time. It was a real letdown to have to stop thinking about plans for an expanded research program and to get down to the realities of making the most of our existing limited facilities and finances.

Despite this handicap, we began to study the effect of different colored light environments on mice. It had been necessary to start quite a breeding colony of rabbits for the pigment epithelial cell experiment. There just wasn't any available space to accommodate the larger rabbit cages, so the only solution was to push aside some of the time-lapse projects involving plants to make way for the rabbit cages. I soon found that the results we were obtaining in breeding rabbits in the ultraviolet transmitting plastic greenhouse were so far superior to the average results obtained in artificially-lighted animal breeding rooms that the delay of the time-lapse sequences involving plant studies was more than offset.

I began thinking about the results of adding a little long wavelength or black light ultraviolet to the ordinary incandescent light source of the microscope and it seemed to me to be quite significant, especially when coupled with the exceptionally satisfactory results obtained in the breeding of rabbits in the ultraviolet transmitting greenhouse. This prompted me to build additional space where laboratory animals could be exposed to natural sunlight conditions through different types of glass and plastic materials that would allow various amounts of natural ultraviolet to penetrate. The additional space also contained a compartment with a simple air curtain that would allow the natural sunlight to penetrate unfiltered in any way. The opening was screened to keep insects out and the air was circulated from the center of the animal room through the various compartments and out the air curtain, in a way that would keep the cold weather out during winter.

The improved results in breeding not only the rabbits in the ultraviolet transmitting greenhouse as compared to the standard artificially-lighted breeding room, but also the differences noted in breeding both mice and rats under the air curtain as compared to the various colored light compartments were almost unbelievable. In breeding laboratory animals it is standard procedure to remove the male from the cage before the litter is born because of his tendency toward cannibalism. However, the male rats in cages exposed to sunlight through ultraviolet transmitting plastic, quartz glass or air curtain were observed to help care for the litter, especially when the female was removed from the cage. Furthermore, the adult male rats appeared decidedly more docile and friendly when handled, whereas those kept under fluorescent light seemed more irritable and developed a tendency to bite.

Although these results were interesting, the numbers of experimental animals did not approach statistical significance. However, later experiments involving larger numbers of animals did begin to show significantly different responses when kept under different colors or wavelengths of light.

In a group of 536 mice born under the air curtain, ultraviolet transmitting plastic or quartz glass, all except 15 survived to maturity. This represented a survival ratio of 97 per cent. Under various types of fluorescent light 88 per cent of 679 mice survived to maturity. Approximately 94 per cent survived to maturity under cool white, warm white and daylight white lamps, but the percentage of survival noticeably declined under the different, deeper-colored lights. The lowest survival rate of 61 percent occurred in the mice exposed to pink fluorescent light.

The animals being kept outdoors under natural sunlight corning through ordinary window glass, ultraviolet transmitting plastic, quartz glass and the air curtain, also showed significantly different responses. The tails of both male and female C₃H mice became spotted and would develop sores under 12 hours daily exposure for three months to pink fluorescent light. At this stage of development, when some of the mice were transferred back to the air curtain, the tails would again appear normal after thirty days. If, however, the mice were left under the pink fluorescent for six months, the tails would appear gangrenous and, bit by bit, slough off until some of the more severe conditions resulted in complete necrosis of the tail. A careful examination of this tail condition revealed no evidence of the presence of any bacteria or fungi.

A subsequent showing of the mice pictures brought the following letter from Phyllis A. Stephenson, M.D., who is now a member of our own Medical and Scientific Advisory Board.

We were trying to find some of the answers ourselves.Three months exposure of the same C₃H strain of mouse during the daylight hours to a new purple, plant growth fluorescent tube would result in the animals losing much of their fur, and after six months under the purple light they would lose almost all of their fur and appear to be in a relatively unhealthy-looking condition. Autopsies performed on some of the animals indicated a normal, healthy condition of the heart tissue in all those from the air curtain compartment, whereas all those from the pink fluorescent light showed an excessive condition of calcium deposits known as calcific myocarditis. The tails of the mice under the pink fluorescent light and the fur of the mice under the purple light were of course exposed directly to the lights. The abnormal responses may therefore have been due to the direct exposure of the tails and the fur to the light, or possibly these results could have been due to the light entering the eyes and stimulating the retinal or oculo-endocrine system which may control the body chemistry. However, the heart tissue is not directly exposed to the light and these results must therefore be mediated in some indirect way, possibly through the eyes and pathway to the endocrine system.

In a simple preliminary experiment, the cholesterol level in the blood of mice kept under dark blue fluorescent light was found to be higher than in the blood of mice under red light. Many of the male mice under blue light became obese; this tendency was not noticed in the females.

These inconclusive observations are mentioned only to suggest the extent to which light might possibly be a variable in such research studies, and again, they emphasize the need for positive scientific control of all light sources used in the laboratory. Consideration might also be given to establishing some standard color for walls, ceiling and floors. In the October 25, 1963, issue of Science, the effects of isolation stress on white rats was reported. A marked difference in the toxicity of isoproterenol between community-caged rats and isolated rats provided a criterion for following the development of isolation stress. According to this group of investigators, the reversibility of isolation stress was also established, the reversal being attributed to the effects of short term versus long term isolation. Short term isolation stress was defined as one to ten days and long term from ten to thirty days. My particular interest in this article centered on the reported condition of caudal dermatitis, or scaly tail, which also followed a reversibility pattern attributed to the short term versus long term isolation stress. Although this condition was not nearly as serious as the condition of the tails of our mice under the pink fluorescent light, the similar reversibility patterns were definitely of interest. Of course the condition of complete necrosis of the tail could not be reversed, but during the early stages of development it seemed quite definite that the reversibility was attributable to the mice being transferred from the pink fluorescent to the full natural sunlight received through the air curtain.

My interview with the principal investigator in charge of the isolation stress study, and all of his co-workers, revealed that coincidentally, at the precise time between that designated as short term and long term isolation stress, the lighting environment of the two groups of animals was drastically changed. All the cages containing the isolated animals were on one large rack at one end of the animal room, with the cage doors directly facing the windows. The colony groups of animals were on another similar rack in a dark area and with the cage doors facing away from the windows. During the interview, it was learned that one of the laboratory assistants had moved the racks when mop-ping the floor and had inadvertently switched their locations. Needless to say, this emphasizes the need for having laboratory light sources under scientific control.

Continuing with our experiments with the C₃H strain of mouse, which is so highly susceptible to spontaneous tumor development, our purpose was to carry out further experiments to determine the length of time required for such tumor development in the animals kept under different light environments. This part of the experiments did, I believe, reveal possibly the most significant data of all of our experimental work. The C₃H strain of mice kept under pink fluorescent light developed spontaneous tumors and died, on the average, in 7 1/2 months. The animals under different types of light with an increasingly wider spectrum showed a progression in life span up to 16 1/10 months. Over 2,000 mice were used in this experiment.

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It is interesting to note that the most extreme adverse conditions regarding not only tumor development but also necrosis of the tails, calcium deposits in the heart tissues, smaller numbers in litters, and difficult behavioral problems, all were caused by pink light.

The question then arises that if these responses are due to the absence of the shorter wavelengths and the influence of the longer wavelengths, why then are some of these responses not most severe under red light—as in the case of the chloroplasts in the cells of Elodea grass? The answer to this is not clear, but consideration might be given to the fact that many nocturnal animals do not see red light because these wavelengths are beyond the range to which their visual receptor mechanism is responsive. Many zoos are now using red light in rooms where nocturnal animals are located, and the animals seem to think it is nighttime and are accordingly more active and interesting to watch. When ordinary lights are turned on the animals usually curl up and go to sleep.

The indication that some nocturnal animals cannot see red light, and the suggestion that other nocturnal animals can "see in the dark" because their eyes are sensitive to infrared is somewhat contradictory.

However, the range of wavelengths to which the visual receptors of nocturnal animals respond may vary with different species. Likewise, the usual receptors may not respond to the precise same range of the longer wave lengths that activate the oculo-endocrine system, which seems to be definitely so with the ultraviolet.

The results of the spontaneous tumor development experiment under different types of lights were indeed quite startling, and several doctors interested in cancer research who had assisted in setting up the proper controls for our experiments agreed that this experiment should certainly be repeated, and several agreed to do so at the various hospital or research laboratories with which they were associated.

Dr. Samuel L. Gabby, who had conducted the expert -ment with the mice in his basement, offered to keep some outside as well if we could make him some sort of portable enclosure with an ultraviolet transmitting cover. We did, and he obtained virtually the same results as shown in the tumor development chart.

I was also asked to show the films and speak at one of the research seminars at The Evanston Hospital, north of Chicago, where Dr. Edward F. Scanlon, one of our trustees, was head of the Tumor Research Committee and had been named as principal investigator in our last N.I.H. grant application. Immediately following my presentation. Dr. Scanlon advised that work was actually in progress in injecting hamsters with several different tumor transplants in connection with their studies of the effectiveness of various anti-tumor drugs. He suggested that they would postpone the injection of the drugs for the time being if I would take half of the animals, selected at random, and keep them in the air curtain compartment in our laboratory animal quarters where they would be subjected to natural daylight. The other half would remain in their regular laboratory quarters under cool white fluorescent tubes. This plan was agreed on.

Dr. Scanlon and several members of his staff periodically visited our laboratory as the project proceeded. The results of this experiment showed that the animals that had received a very fast acting tumor transplant showed little difference in the life span from those under the air curtain and those that remained in the regular animal laboratory facilities at the hospital under cool white fluorescent tubes. However, those animals that received a slower acting type tumor transplant did show a significant difference. The animals remaining under the cool white fluorescent tubes showed an average life span of 29 days, whereas those kept under the air curtain averaged 43 days.

With the unanimous approval of the entire research committee of the hospital. Dr. Scanlon wrote a report, together with a request for a small research grant to carry on further studies, and submitted this to the Illinois branch of the American Cancer Society. The Illinois branch in turn forwarded the report and request on to the American Cancer Society headquarters in New York City, and in due course the following reply was received from the Illinois office:

The power and authority of such a distinguishedscientific committee is awe inspiring. There is no recourse. Their word is final. Their combined knowledge and wisdom is supreme. But how can anyone be so certain as to what cannot cause cancer until it is known what does? To say that considering light as a variable would only further confuse the issue is difficult to reconcile with the basic concepts of research.

Being turned down again was discouraging, to say the least, but none of the reasons yet given by any reviewing committee has offered any convincing evidence that light energy might not be a missing link. In fact, all of the reasons given opposing the suggested light hypothesis indicated to me a great need for additional and determined pursuit of the subject.