James G. Snedecor

Studies on the chick glycogen body: Effects of hormones and normal glycogen turnover ☆

Abstract The administration to chicks of hormones which decidedly affected blood glucose, liver glycogen, and muscle glycogen was shown to have no effect, except in two cases, upon the glycogen content of the glycogen body. Corticosterone in one experiment and epinephrine in one experiment out of five increased glycogen-body glycogen. The hormones used included regular insulin, glucagon-free insulin, glucagon, epinephrine, cortisone, hydrocortisone, corticosterone, and mammalian growth hormone. Chicks fasting for as long as 5 days after hatching failed to show significant changes in glycogen-body glycogen concentration. Glycogen body weight and total glycogen increased gradually with age during an 11-week period. Glycogen concentration reached a peak (32%) at 3 weeks, gradually declined to the hatching level (25%) at about one month, then continued to fall and reached 21% by the eleventh week. Week-old chicks were killed 3, 8, 18, or 48 hours after injection with 50 μc of glucose C 14 , and the level of isotope in the glucogen-body glycogen was determined. The glycogen was digested with β-amylase to separately determine the activities of the peripheral tiers (maltose) and inner core (limit dextrin) of the glycogen. The specific activity of glycogen-body glycogen as per cent of the injected specific activity was insignificant at 3 hours and 0.015%, 0.040% and 0.016% at 8, 18, and 48 hours respectively, indicating an incorporation and release of the glucose C 14 during the 48 hour period. The replacement of glucosyl units was greater in the maltose fraction of the glycogen than in the limit dextrin. These changes are interpreted as an indication that although the glycogen concentration remained constant, glycogenesis and glycogenolysis occurred.

Liver hypertrophy, liver glycogen accumulation, and organ-weight changes in radiothyroidectomized and goitrogen-treated chicks

Abstract The effectiveness of radiothyroidectomy and of the feeding of thiouracil, propylthiouracil, and methimazole in producing hypothyroid changes in young cockerels was studied. Changes in glycogen content and relative size of the liver are emphasized as sensitive indicators of severe hypothyroidism. Changes in body, comb, testes, thyroid, and bursa weights are also considered. It was concluded that: (1) 0.1, 0.15, and 0.2% thiouracil (TU) are equally effective in producing hypothyroid changes up to age 3 weeks. (2) An equimolar amount of propylthiouracil (PTU) is slightly more effective than 0.2% TU up to age 30 days. (3) Radiothyroidectomy (RT x ) and 0.2% PTU are equally effective to age 5 weeks, but PTU has a greater depressive effect on body weight because of its probably disagreeable taste and consequent effect upon food intake. (4) An amount of methimazole at 0.1% was as effective as 0.2% or 0.3% TU to age 5 weeks, but 0.05% and 0.025% methimazole were relatively ineffective except in thyroid weight changes. (5) Amounts of iodinated casein one-third to one-fourth the amount equivalent to normal thyroid hormone secretion when added to TU diets allowed normal growth in most organs measured, and normal liver glycogen, but the thyroid hypertrophied. Further reduction of iodinated casein to one-fifteenth to one-twentieth the normal thyroid hormone equivalent resulted in moderate liver hypertrophy and above normal glycogen deposition. (6) The twice daily injection of PTU produced liver changes characteristic of TU feeding. (7) The effects of TU on liver change persisted from between 27 and 50 hours after the withdrawal of TU from the feed. (8) Onset of liver changes after initiation of TU feeding required 2–4 days depending on age, and occurred earlier than changes in thyroid weight. (9) Interruption of a TU feeding regime by an overnight fast, although lowering liver glycogen markedly, did not obviate the TU effect during refeeding. (10) Withdrawal of normalizing exogenous thyroxin from RT x chicks resulted in liver hypertrophy and increased glycogen accumulation within 48 hours. Comparative responses of liver in rat and chick are discussed.

Comparison of subnormal multiple doses of l-thyroxine and l-triiodothyronine in propylthiouracil-fed and radiothyroidectomized chicks (Gallus domesticus)☆

1. 1. The physiological potencies of l-thyroxine (l-T4) and l-triiodothyroxine (l-T3) are equal in propylthiouracil (PTU)-fed radiothyroidectomized (RT) chicks. 2. 2. Propylthiouracil does not seem to interfere in the peripheral activity of T4 or T3 in the chick. 3. 3. Liver hypertrophy and liver glycogen accumulation are distinct criteria of hypothyroidism in the chick and are restored to near normal levels by small daily doses of T4 or T3. 4. 4. The thyroid enlargement subsequent to the feeding of PTU is further increase by the administration of multiple subnormal doses of T4 or T3. 5. 5. The poor growth rate of PTU-fed and RT chicks compared to control chicks is due to decreased food intake. The apparent digestibility of protein, fat, and energy, as well as the efficiecy of food utilization are affected equally by T4 or T3 in PTU-fed or radiothyroidectomized chicks.

Effect of radiothyroidectomy in chicks with emphasis on glycogen body and liver

White Rock chicks injected with 1.5 mc I131/100 gm at 5 or 9 days and autopsied from 8 to 43 days later were considered severely hypothyroid by several criteria. Glycogen-body weight was reduced in one experiment but not in another. Glycogen concentration in the glycogen body was not affected. Liver weights of radiothyroidectomized birds were the same as the control, but on a per cent body weight basis the livers were significantly enlarged. Values for liver glycogen in the radiothyroidectomized birds were high and remained high in chicks fasted 18 hours. Radiothyroidectomy had little effect on blood glucose or muscle glycogen. Weights of testes, combs, and spleens were definitely decreased in the hypothyroid birds, whereas the adrenal weights were similar to the controls despite the marked body weight differences.

Interaction of thyroid hormone and androgen on body weight, comb, and liver in cockerels

Comparisons of the effects of thiouracil treatment, surgical thyroidectomy, and radiothyroidectomy on body and organ weights of White Leghorn chicks were made to determine the most effective method of producing hypothyroidism. Radiothyroidectomy was deemed most effective and in a second experiment radiothyroidectomy, castration, and replacement of thyroid hormone and/or androgen were utilized in setting up the following groups of male chicks: (1) Control, (2) Castrates, (3) Thyroidectomized, (4) Thyroidectomized castrates, (5) both procedures plus partial thyroid hormone replacement, (6) both procedures plus exogenous methyl testosterone, (7) both procedures plus androgen and thyroid. Castration was done when the birds were about 1-week-old. Radiothyroidectomies were done on Day 11. Hormones were mixed with feed. Comb size and body weight were measured weekly, and daily food consumption was measured throughout. The experiment was terminated when the birds were 5 weeks old, and the following conclusions were drawn from the measurements made: (1) Castration had no effect on body weight in the presence or absence of thyroid hormone, whereas thyroid lack decidedly reduced body weight gain. (2) Exogenous androgen reduced food intake and body growth in Group 6, but not when endogenous or exogenous thyroid was present. (3) Both androgen and thyroid hormone are involved in comb growth, but either alone resulted in more growth than occurred in the thyroidectomized castrates. (4) Some androgen is produced by the significantly smaller testes of the thyroidectomized chick. (5) Lack of thyroid hormone (Groups 3, 4, and 6) resulted in larger relative liver weights and greatly increased liver glycogen. (6) Subnormal exogenous thyroid hormone (Group 5) gave less than normal body and comb growth, but allowed normal liver size and glycogen content to be maintained. (7) Thyroid weight was significantly reduced by castration. (8) The highest comb water content was in those groups having both thyroid and androgen. (9) Adrenal weight was unaffected by any of the treatments.

Some effects of single doses of triiodothyronine and thyroxine in hypothyroid chicks

Abstract Three-week-old propylthiouracil chicks were given a single injection of 1, 10, or 100 μg of T 3 and, in another experiment, T 4 . Liver weight and liver glycogen were determined at 24, 36, 48, 60, 72, and 96 hours and were found to be lowered maximally at 24 hours at all dose levels. The 10 and 100 μg doses of both hormones were almost equally effective until after 48 hours; thereafter the 100 μg dose showed more prolonged effectiveness. The 1 μg dose of both T 3 and T 4 was somewhat less effective at 24 hours and much less effective after 48 hours compared to the higher doses. For 100 μg, neither liver weight nor glycogen had again reached the hypothyroid level at 72 hours, but T 4 seemed to have somewhat more prolonged effects than T 3 . Serum cholesterol was lowered maximally at 60 hours by both hormones. Thyroid weight was reduced by the higher doses at 48 hours, but not earlier, and the weight reduction persisted through the 96th hour for the 100 μg level of T 4 . In a third experiment, T 3 and T 4 were compared at the 10 μg dose level. Liver weight was reduced by both hormones at 18, 24, and 36 hours but not at 12 hours. Glycogen was markedly reduced by both hormones from 12 through 36 hours; the T 3 effect was greater at 12 hours but less at 24 and 36 hours. At 18 hours after injection, T 3 and T 4 were equally effective.

Influence of age on the development of hypothyroidism by propylthiouracil feeding in the chick (Gallus domesticus)

Abstract 1. 1. Propylthiouracil (0·15 per cent) was fed in mash to chicks aged 16 and 37 days for a period of 27 days and then were taken off propylthiouracil (PTU). 2. 2. Body weight, liver weight, liver glycogen, thyroid weight, plasma cholesterol and serum glutamic pyruvic transaminase (SGPT) were determined at various time intervals after initiation of PTU feeding and then when taken off PTU. 3. 3. On initiation of PTU feeding the hypothyroid changes mostly occurred earlier and were more severe in the younger chicks than in the older ones. 4. 4. Reverse changes (i.e. towards normal values) after taking chicks off PTU were faster in the older birds compared to the younger ones. 5. 5. Irrespective of the age at the start of PTU feeding, it took one week before normal growth rate was resumed after taking chicks off PTU. 6. 6. Results of these studies suggest that younger birds show more severe symptoms to the hypothyroid effect of PTU. However, given enough time after taking chicks off PTU, except for body weight, all the biochemical changes of hypothyroidism disappear, at least under the conditions of present study.