C. M. McCay

Nutritional Studies of the Webbing Clothes Moth Tineola bisselliella Hum

SINCE a complete knowledge of the nutritional requirements of an insect is an important tool in studying economic control, and since the peculiar feeding habits of the clothes moth r nder it an object of interest to the student of nutrition, it was considered worth while to undertake a detailed study of the effect of various food factors upon the life-cycle of the webbing clothes moth, Tineola bisselliella. Furthermore, such studies are of value from the point of view of evolution. Material which will contribute to the fund of information regarding the food requirements of representatives of the various phyla is sought by the general biologist and the comparative physiologist, as well as by students in the more specialized fields of economic entomology or nutrition. The general plan of the experiments undertaken has been a determination of the effect of various constituents of the diet on the duration of the life-cycle, in days. The lifecycle of an insect is defined as the time elapsing from the laying of the egg to the emergence of the adult insect. Such an expression of results rests on the assumption that an optimum diet allows development in a minimum of time. A similar technique has been used for Tribolium studies (Sweetman and Palmer, 1928) and for studies on the Mediterranean flour moth (Richardson, 1926). Physiological or nutritional studies upon cold-blooded animals must be rigidly controlled in regard to physical environment. The need for careful regulation of temperature, humidity, and consistency of the diet is particularly important where the animal lives surrounded by its food. Such animals have never had to adapt themselves to rapid changes in temperature and humidity. Attempts have been made in these experiments on clothes-moth larvae so to regulate other conditions that dietary constituents remain the only variables. Diets were brought to a finely divided condition by grinding through the 1/2-mm. screen of a Wiley mill or by pulverizing them in a ball mill. Diets of more than one constituent were mixed by grinding with a mortar and pestle. The diet to be tested was sampled into shell vials of 20X 40 or X 80 mm. Newly hatched larvae were then transferred to the vials by means of a camels-hair brush. All larvae were examined under a binocular after transfer, to eliminate any injured animals. Cotton plugs or very fine muslin squares were used to cover the vials and prevent the escape of the larvae. Thirty animals were used in most experiments. The number of larvae per vial varied from one to five, but three individuals per vial were finally selected as the most satisfactory number. The temperature was maintained at 250 C. in a thermostatically controlled incubator. The humidity was roughly controlled by the presence of a dish of water in the incubator. In certain of the experiments a relative humidity of 75 per cent (Griswold and Crowell, 1936) was maintained by keeping the vials in museum jars over a saturated solution of sodium chloride. The vials were examined weekly for five weeks, and thereafter were examined daily for adult moths. Records were kept of the date on which the eggs were laid and the date of emergence of the adult moths. 368 [PHYSIOLOGICAL ZO6iLOGY

Diet and aging.

Publisher Summary This chapter analyzes the role of diet in aging process. Any consideration of the nutrition of man during the later years of life must recognize that many interrelated factors create special problems in the nutrition of the aged. Some of the factors that tend to create malnutrition during the later years of life are the following: low incomes, poor facilities for food preparation, ignorance of nutritive values, mental deterioration, worry from insecurity, poor cooking facilities, living alone, physical handicaps and lack of exercise. Many special physical factors also contribute. Research with animals indicates how profoundly both the life span and the terminal diseases of old age are modified by such factors as growth rate during the earlier periods of life. In this chapter, mineral metabolism in old age is discussed. Effect of calcium and other inorganic elements on lifespan is analyzed. Effect of vitamin A on longevity is described. A discussion on water soluble vitamins, fats, vegetarian diets, and low-calorie diets is also presented.

Effect of Sulfamerazine and Exercise on Life Span of Rats and Hamsters

Rats and hamsters of both sexes were divided into exercise and non-exercise groups with and without small amounts of sulfamerazine in the diet. In every case rats on exercise lived longer than their controls. The females outlived the males while hamster males lived slightly longer than females. Sulfamerazine had a significantly beneficial effect on life span of rats and apparently increased that of male hamsters. All rats fed sulfamerazine attained higher maximum weights than their controls. There was no consistent change in bone densities.

NUTRITIONAL EXPERIMENTS ON LONGEVITY

Most scientific advances in the fields of biology and medicine have been made by a series of observations upon animals, with each study consuming only a few weeks or a few months of time. In surgical research one may remove the gall bladder or a kidney from an animal, watch it for a few weeks or months, and then undertake another study. During such brief periods the animal body is able to withstand tremendous insults both internally ind externally. The animal may have several diseases of bacterial origin and be something of a museum for the parasitologist. It may be fed a miserable diet but its body reserves protect it from death. It may live in dark, humid quarters but survive. It may even be poorly treated by the caretaker and live.in filth. For a few months a dog may survive under such conditions. But if one extended the study to cover a period of years the animal would perish. One would not know which of many variables produced premature death. In many fields, such as toxicology, the temptation is eternal to test high concentrations of a given chemical for brief periods in order to avoid the expense and tediousness of long-term studies with low levels of ingestion. At the end, however, the results are usually applied to human beings ingesting low levels of chemicals for long periods of time. Examples of such testing in recent years can be drawn in large numbers from studies upon fluorides in water supplies, from studies of the effects of spray residues upon plant foods and from tests of cancer-producing cheInicals used in foodstuffs. Thus, much of all the testing of fluorides for use in water supplies has been performed upon rats fed high concentrations of fluoride, such as 50 parts per million, for periods of one to two hundred days. From the results of such testing it is then concluded that it is safe to use 1 part per million of some fluoride such as silicofluoride in the water supply of some large city such as Washington, D.C. In order to make real progress in the study of chronic diseases in man, such as

Certain Physical and Chemical Characteristics of the Lake, Loch Leven, Rainbow, and Brook Trout

Abstract The changes in the weight of the organs and the body composition (proportions of moisture, proteins, fat, and ash) of four species of trout have been followed during normal growth and after retardation of growth by underfeeding. The eyes tend to continue growth when the fish are underfed. Retarding of growth results in loss of fat and protein accompanied by an increase in the ash content. Underfeeding also results in the loss of fat in trout livers, and in some instances this loss of fat is accompanied by an increase in the iodine number values.

PANEL DISCUSSION ON PROPER NUTRITION FOR THE OLDER AGE GROUP

Moderator: CLIVE M. MCCAY, PH.D., Professor of Nutrition, Cornell University, Ithaca, N.Y. Panelists: RICHARD H. FOLLIS, JR., M.D., V. A. Central Laboratory for Anatomical Pathology and Research, Armed Forces Institute of Pathology, Washington, D.C. NORMAN JOLLIFFE, M.D., Director, Bureau of Nutrition, Department of Health, New York, N. Y. WILLIAM B. KOUNTZ, M.D., Assistant Professor of Clinical Medicine, Washington University, St. Louis, Missouri. S. O. WAIFE, M.D., Editor-in-Chief, The American Journal of Clinical Nutrition, New York, N. Y.