James H. Shaw

Dental Caries in the Cotton Rat

An experimental animal which is readily susceptible to dental caries has long been recognized to be the prerequisite for research in the causes and control of dental caries. Shaw, Schweigert, Mclntire, Elvehjem and Phillips (1) have given evidence that the cotton rat (Sigmondon hispidus hispidus) is much more susceptible to dental caries than any other experimental animal previously reported. The evidence presented indicates the opening of a fertile field for dental research. The method of production and the description of the carious lesions in the cotton rat are to be reported here.

Pathological Studies of Acute Biotin Deficiency in the Rat.

Summary The pathology occurring in the thymus, testis, epididymis, skin and muscles of the acutely biotin-deficient rat is reported. No degeneration of the spinal cord or sciatic nerves was observed despite the very extreme spasticity which occurred in many of these acutely deficient animals.

A Call for Improved School Leadership

Evaluating the quality of ones work should not be limited to students and teachers; leaders also must be evaluated and encouraged to improve.

Dental Caries in the Cotton Rat. V. Influence of Strain Variation on the Caries Susceptibility.

Summary A difference in susceptibility of different strains of cotton rats to dental caries has been observed and shown to be statistically significant. Preliminary results from second generation offspring indicate that their susceptibility is similar to that of the parent stock.

Curative Effect of Pantothenic Acid on Adrenal Necrosis.

Summary Rats receiving only our basal ration J36 showed an hemorrhagic cortical necrosis of the adrenals after 4-6 weeks. This condition was prevented by calcium pantothenate. Choline did not prevent but rather aggravated the condition. Acid autoclaved liver extract prevented the condition, but its action may have been due to its pantothenic acid content.

Dental Caries in the Cotton Rat. IV. Inhibitory Effect of Fluorine Additions to the Ration.

Summary Some inhibition of caries resulted when 45, 90, or 135 p.p.m. of fluorine were ingested as supplements to a sucrose basal ration. Depigmentation of the incisors appeared when 45 or more p.p.m. of fluorine were incorporated in the diet while mottling of the third molars occurred when 225 or more p.p.m. were fed. The ingestion of 225 or 450 p.p.m. of fluorine caused a 90%. decrease in caries incidence. Thus the amount of fluorine necessary to inhibit caries to this degree was sufficiently high to cause mottling of the developing teeth. The inhibitory effect of dextrin upon caries development could not be explained on the basis of its fluorine content.

Studies on Manganese Deficiency in the Rat

Summary Pronounced manganese deficiency in the rat has been produced by use of rats weaned without access to manganese. This deficiency resulted in definitely impaired growth in the male and the female rat. In the manganese-deficient female rat estrous cycles were irregular or absent, and there was a marked delay in the opening of the vaginal orifice. A manganese deficiency in the male rat caused testicular degeneration and complete sterility due to lack of spermatozoa production. Both male and female manganese-deficient rats were unable to reproduce. No histological abnormalities were detected in the adrenal, kidney, pituitary, and thyroid of the manganese-deficient rat. The deficiency did not result in reduced ascorbic acid content of tissues, nor did ascorbic acid stimulate the growth of the manganese-deficient rat. Synthesis of ascorbic acid from mannose by rat liver and other tissues in vitro could not be obtained with or without added manganese. A reduced arginase concentration in the liver of the manganese-deficient rat was found. There were no essential differences in the activity of the intestinal dipeptidases studied.