Three groups of goldfish were fed diets containing 25% fat. The diets for the three groups differed in the degree of unsaturation of these fats. Pilchard oil (iodine value 181.7), herring oil (iodine value 128.4), and lard (iodine value 66.2) were the fats used. Heat tolerance of the fish was then tested by holding them at a constant high temperature and observing the time of death. Variations in the ability of the groups to withstand high temperature were correlated with differences in the degree of unsaturation of their extracted fats. The iodine value of the herring oil diet was very close to that of the fats of the goldfish prior to feeding and no change in the value for fish fed on this diet was observed. Each of the other two diets changed the degree of unsaturation of the goldfish fats by approximately 54% of the maximum theoretical change. These changes modified the heat resistance of the fish. The degree of modification of heat tolerance, however, cannot be strictly correlated with the degree of change of unsaturation of fats and it is concluded that factors associated with differences in melting point rather than melting point of the fat itself are probably involved in heat resistance.

The gastro-intestinal endocrine structures have been considered to be independent of other endocrine glands and not interrelated with them in activity (Grossman, 1950). Because of the very definite atrophy of the pancreas that occurs after hypophysectomy, and the known relationship between certain intestinal hormones and pancreatic function, it was felt that the influence of the pituitary gland on the levels of those intestinal hormones which affect pancreatic secretion should be investigated. Both the secretin and pancreozymin mechanisms were considered. Since secretin could be studied morereadily, it was decided that this should be examined first. Experiments were therefore undertaken to determine the effect of hypophysectomy on the level of secretin in the intestine of the rat. MATERIALS AND METHODSIn the experiments to be reported, intestinal extracts were prepared by a slight modification of the method of Luckhardt, Barlow & Weaver (1926).Wistar and Sprague-Dawley rats were the test animals. Immediately after sacrifice by decapitation, the entire small intestine from the pylorus to the ileocolic sphincter was removed and washed through with cold water. One end of the gut was then clamped and filled with 0-15 N-HCI, and the other end clamped. The acid was allowed to remain in contact with the mucosa for 20 min, afterwhich itwas drained out into a beaker and the gut refilledwith fresh 0-15N-HCI. After afurther 20 min, the second extract was drained into the first. The intestine was then washed through with a few millilitres of the acid, and the washings added to the extract.The total solution was heated quickly to 850 C and brought to a pH of 5-3-6 with 1.0 N-NaOH. This precipitated the protein matter which was filtered off under suction. The filtrate was acidified with HCI to a pH of about 2 and evaporated down to 5 or 6 ml. in an evaporating dish over a low flame. The temperature of the solution was not allowed to rise above 855 C. The residue was placed in a small flask, frozen quickly and kept frozen until required. Before use, the crude secretin solution was thawed, neutralized to a pH of 6-2 and made up to a volume of 10 ml. by the addition of distilled water. Such solutions were found to be active in doses as small as 0-5 ml.In most of the experiments, in order to have enough material with which to work, two rats were used for each test solution.Acetone-dried extract of hog mucosa, prepared as outlined by Burn & Holton (1948) served as the standard for these tests. The activities of the unknown solutions were compared with the

Recently we demonstrated that vagotomy resulted in decreased secretin but increased pancreozymin content of small intestine of the rat ( 1 ) . Routine observations on stomachs revealed a substantial increase in weight of this organ in the vagotomized as compared to control animals. The present study was undertaken to confirm and extend this finding.Methods. Female rats of Wistar strain were paired according to weight. A subdiaphragmatic bilateral vagectomy was performed on 1 member of each pair, a mock operation on the other. Vagotomized and control animals were maintained in individual cages on a paired feeding regimen for 7-63 days. Animals were fasted 12 hours before sacrifice. The rats were sacrificed in pairs, stomachs and intestines removed, and wet weight, dry weight, and weight of fat free residue of tissues determined. Weight of food residue was also noted. In 1 2 cases glandular and non-glandular stomachs were separated and weight measurements made for the 2 portions.Results. Mean values for measurements are given in Table I.Discussion. The results show that following vagotomy a marked increase in stomach tissue weight and a less dramatic reduction in intestinal tissue weight occurred. Changes in fat and water content, which in stomachs seem to have occurred in the glandular rather than muscular portion, are too small to account for changes in weight.I t is possible that mechanical distension due to retained food in some manner caused hypertrophy of the storxachs. However, in 2 vagotomized animals there was no evidence of food retention, yet the stomachs were enlarged. I t is obvious from the data that the observed weight changes in stomachs of vagotomized rats are not due to edema or fat deposition. Nitrogen determinations made on some of the fat free residues indicate that increase TABLE I. Effect of Vngotoiiiy oii Weight and Coiiipositioii of Stoniachs :rnd Sinall Iiitestiiics of Rats.

Crude HCl extracts were made from the intestines of vagotomized albino rats and their paired fed controls. Using a simple cross-over design requiring two rabbits for each assay, the extracts were compared for secretin and pancreozymin activity. Significant differences in both the volume and amylase activity of the pancreatic juice secreted in response to 5-ml injections of the extracts were observed. It was concluded that vagotomy led to a reduction in the secretin activity, but an increase in the pancreozymin activity of the intestines.

The finding of Dorchester & Haist (1952a) that hypophysectomy led to a reduction in the secretin content of the intestine of the rat, demonstrated that the pituitary gland influenced the activity of endocrine structures concerned with the elaboration of secretin. The results of the present investigation indicate that an important part of this influence is exerted by the anterior portion of the gland. This conclusion is based on the finding that crude extracts of the anterior pituitary and relatively highly purified growth hormone and ACTH preparations from the anterior portion of the gland prevented the lowering of intestinal secretin in the hypophysectomized animals. A preliminary report of part of this work has appeared in Federation Proceedings (Dorchester & Haist, 1952c). MATERIALS AND METHODSThe methods for the extraction of rat secretin and its assay have been described previously (Dorchester & Haist, 1952a, b). Hypophysectomized and intact Wistar and Sprague-Dawley rats were the test animals. Rats were paired according to weight, one member of each pair serving as the test animal, the other as the control. In the experiments using hypophysectomized rats, each control animal received the same amount of food as the corresponding test rat. Control and test rats were sacrificed at the same times. In one series of experiments on hypophysectomized animals the test rats received desiccated thyroid gland in the food. In another, the test rats were injected with a crude saline extract of the anterior-pituitary gland. In a third series, rats were injected daily with growth-hormone preparations, and in a fourth, ACTH was administered. Further experiments were undertaken in which anterior-pituitary extract, growth-hormone preparations and ACTH were injected into intact rats.