Curt P. Richter

On the phenomenon of sudden death in animals and man.

Summary A phenomenon of sudden death has been described that occurs in man, rats, and many other animals apparently as a result of hopelessness; this seems to involve overactivity primarily of the parasympathetic system. In this instance as in many others, the ideas of Walter Cannon opened up a new area of interesting, exciting research.

Graying of Hair Produced by Ingestion of Phenylthiocarbamide

Summary (1) After being placed on a stock diet and given phenylthiocarbamide solution as the sole source of fluid, with one exception 23 black or black hooded rats showed definite graying, some as early as 27 days and all within 58 days. (2) Approximately 83 days after the phenylthiocarbamide solution was replaced by tap water, five rats that had shown marked graying turned completely black again. (3) The experiments showed that graying may result from a positive factor in the diet, a poison, as well as from a deficiency of some factor.

Cataracts Produced in Rats by Yogurt

Rats kept on an exclusive diet of yogurt avidly ate the yogurt, grew at a normal rate, were normally active, mated, conceived, and gave birth to normal, healthy litters. However, all of the rats developed cataracts. Cataracts appeared in young rats 2 to 3 months, and in adult rats 4 to 6 months, after initiation of the yogurt diet. Cataracts first manifested themselves in small vacuoles at the periphery of the lens and then in small striae extending toward the center of the lens. These striae progressively became longer, more coarse, and numerous until they coalesced, finally forming a mature white lens. The high content of galactose in commercially available yogurt could account in full for appearance of cataracts in 100 percent of the experimental animals. The cataracts appear to be the same as those produced by diets with a high content of galactose.

Age and Species Variation in the Acute Toxicity of Alpha-Naphthyl Thiourea.

Summary Marked age variation in the susceptibility of wild Norway rats to acute poisoning with a-naphthyl thiourea has been found, with suckling rats about 7 times as rehistant as adults. This reGstance was found to decrease with increasing body weight, levelling off for adults at an LDSo between 6 and 8 mg/kg body weight. The difference found between adult males and females was within the limits of error and is therefore not considered significant. Adult animals of other species also varied Markedly in susceptibility to acute ANTU poisoning. Korway rats, dogs and mice were killed by amounts less than a hundred milligrams per kilogram. Alexandrine rats, guinea pigs, and cats required several hundred milligrams, while chickens and monkeys survived doses of several grams per kilogram body weight. Large amounts of pulmonary edema were found only in Norway rats, dogs, mice and cats.

Biological Factors Involved in Poisoning Rats with Alpha-Naphthyl Thiourea (ANTU).∗

Summary 1. Adult domestic Norway rats were found to accept ANTU when mixed with the stock diet in concentrations at least as high as 10%. In all concentrations from 0.1% to 10% inclusive the ANTU-poisoned food killed 100% of the rats, Lower concentrations of ANTU-poisoned food gave a 100% survival. 2. When fed sublethal concentrations of ANTU food from 0.05%) to 0.005% inclusive for 14 days, the rats developed a marked tolerance and refusal. Lower concentrations failed to produce either. 3. In some rats the tolerance disappeared at the end of 16 days and was almost imperceptible in all of the rats at the end of 30 days. 4. The refusal decreased after 16 days, though in some animals it was definitely present even at the end of 30 days.

Self-selection of diets

Summary The results of these studies have shown (1) that a close relationshipexists between appetite and dietary needs; (2) that animals make beneficial selections from purified substances, even better than from natural foods; (3) that we have a new tool for the investigation of a variety of nutritional problems (up to the present the results have been largely confirmatory of biochemical studies; in the future we hope with this method actually to be able to point the way to new relationships); and (4) that all of the dietary self-selection activities may be regarded as total organism responses by means of which the organism maintains a constant internal environment.

Decreased carbohydrate appetite of adrenalectomized rats.

Summary 1. Five rats were given access to a 3% solution of sodium chloride, tap water, dry dextrose, and the saltless stock diet in 4 separate containers. 2. After adrenalectomy the rats greatly increased their intake of sodium chloride, decreased their intake of dextrose, but continued to eat about the same amount of saltless stock diet as before. They showed a small increase in water intake. 3. Daily treatment with desoxycorticosterone decreased the intake of sodium chloride solution and tap water to the normal levels and increased the dextrose intake nearly to the normal level. 4. Thus it was shown that adrenalectomized rats have a definitely decreased appetite for dextrose, as well as an increased appetite for sodium chloride.

A study of taste and smell of heavy water (99.8%) in rats.

Summary Restricted to heavy water (99.8%), rats drank it freely for the first day, then they drank progressively less and died within 14 days. When given a choice between distilled water and heavy water (99.8%) rats avoided heavy water, partly by virtue of some deleterious effects of heavy water and partly by virtue of a faint smell of heavy water with which the untoward effects could be associated. Rats did not taste heavy water. Whether a higher viscosity of heavy water plays any part could not be determined. Apparently the low intensity of any untoward effects of heavy water and the faintness of its smell could explain the erratic variability of the reactions of rats to heavy water that put it in a different category from other substances tested so far.

Comparative Numbers of Fungiform and Foliate Papillae on Tongues of Domestic and Wild Norway Rats.

Summary 1. The number of fungiform and foliate papillae were counted on the tongues of 100 recently trapped wild Norway rats and of 20 wild Alexandrine rats, and compared with the number on the tongues of 103 domestic Norway rats. 2. The number of fungiform papillae on the tongues of the domestic Norway rats ranged from 114 to 221, with a mean of 178.3, while for the recently trapped wild Norway ancestors it ranged from 167 to 271, with a mean of 217.9, and for the Alexandrine rats it ranged from 147 to 231, with a mean of 191.5. The mean of the domestic Norway rat thus showed a 17% reduction from that of its wild ancestor. 3. The number of foliate papillae ranged from 8 to 16 for the domestic rats, with a mean of 11.98, and ranged from 7 to 20 for the wild Norways, with a mean of 11.46. The 2 strains thus showed essentially the same number of foliate papillae, but both showed fewer than are found in Alexandrine rats, in which the number of papillae ranged from 9 to 18, and had a mean of 13.5. 4. In general, both types of papillae were more uniform in size, structure and distribution in the wild than in the domestic strains.

Nutritive Value of Dextri-Maltose Determined by the Single-Food Choice Method

Summary 1. Twelve female rats kept on a diet in which dextri-maltose constituted the sole source of nourishment survived on the average 85 days. 2. These rats lived 48 days longer than rats of the same weight kept on a single food diet of dextrose or sucrose; and 11 days longer than rats kept on dextrose with access to the 0.02 per cent solution of thiamine hydrochloride. 3. Their food intake was higher and they lost weight at a slower rate than the dextrose and thiamine rats. Their activity, water intake and vaginal smears were essentially the same. 4. It was concluded that the dextri-maltose contains sufficient amounts of thiamine to utilize to its fullest the available carbohydrate.