Perianna Kumaresan

Effect of Pinealectomy and Melatonin on Feed Consumption and Thyroid Hormone Secretion Rate.

Summary The effect of pinealectomy upon feed consumption and thyroid hormone secretion rate was studied in Sprague-Dawley-Rolfsmeyer female rats. Feed consumption was increased 5.77% in association with an increase of 11.8% in TSR. In a second group of 16 rats, daily injection of 40 μg/day of melatonin depressed feed consumption 12.0%, whereas injection of 20 μg/day of melatonin into young rats depressed TSR 16%.

Effect of Litter Size Upon Milk Yield and Litter Weight Gains in Rats

Summary A study is reported concerning the influence of litter size in rats on the estimated milk yields and litter weight gains on days 14 to 20, and on the DNA of the mammary glands on day 20. On day 14 of lactation, the mean milk yield increased from 5.6 g with 2 to 16.4 g with 12 in the litter. The milk yield in most groups increased until the 18th day, then decreased on day 20. The milk available/pup on day 14 was 2.8 g for the 2-pup litters and declined gradually to 1.4 g for the 12-pup litters. The litter weight on day 14 was 68.3 g for litters of 2 and increased gradually to 287.1 g for litters of 12. The gain per pup was greatest for litters of 2 and then declined with increasing litter number. At the 20th day, the DNA for litters of 2 was 8.9 mg/100 g bw and increased gradually with increasing litter size to 13.6 mg for litters of 12. The RNA also increased with increasing litter size up to 10.

Effect of Alloxan on Feed Consumption in Rats.

Summary A group of 25 mature female Sprague-Dawley-Rolfsmeyer rats weighing a mean of 223 g consumed a mean of 5.88 g/100 g bw of Purina Lab Chow daily during a 2-week control period. When alloxan was injected intraperitoneally at a level of 15 mg/100 g bw to induce chronic diabetes, feed consumption declined to a level 67% below the control period, then began to increase. Eight rats died during the first week following treatment. The 17 surviving rats increased feed consumption 36% during the 7th to 12th days and 56% during the 13th to 18th days. These data show that induction of chronic diabetes by alloxan increases feed consumption by over 50%.

Effect of alloxan on feed consumption and on replacement therapy with graded levels of insulin in rats.

Summary Alloxan diabetes was induced in a group of 18 female Sprague-Dawley-Rolfsmeyer rats weighing a mean of 237 g. Prior to treatment they consumed a mean of 13.07 g/day and 5.18 g/100 g BW. Following treatment they consumed a mean of 22.13 g/day and 9.46 g/100 g BW of Purina Lab. Chow daily during a 10-day period, an increase of 69%/day and 83%/100 g BW. Graded levels of insulin (1 to 4 u) were administered during 6-day periods. On 2 u/day, feed consumption decreased 9% (non-significant), on 3 u 20% (significant) and at 4 u a highly significant decrease of 23%/100 g BW was observed. At the 3 and 4 u level, 2 and 5 rats died.

Effect of advancing age on thyroid hormone secretion rate of male and female rats.

Summary The thyroid hormone secretion rate (TSR) of the same group of 36 male rats was estimated at 30 days and at 30-day intervals to 120 days. They declined from a mean of 1.40 μg/100 g bw to 1.03 μg at 120 days or 26%. A group of 118 male rats at 30 days of age had a mean TSR of 1.34 μg 100 g bw with a range from 0.75 μg to 2 μg /100 g bw. The TSR of a group of 29 females at 30 days of age was 1.47 μg/100 g bw and gradually declined to 0.87 μg at 240 days of age or 41%. It was shown that the TSR of both male and female rats decline with age but the rate of decline may vary in different groups of animals.

Effect of Graded Levels of Lactogenic Hormone upon Mammary Gland Growth and Lactation in Rats.

Summary Lactogenic hormone was administered subcutaneously at 1, 2 or 3 mg to lactating rats each day during days 7 to 19. Milk yields were obtained after a 10-hour isolation period of dam from pups on days 14, 16, 18 and 20 of lactation. One mg of lactogenic hormone significantly increased yield on days 18 and 20; 2 mg on days 16, 18 and 20; and 3 mg on days 14, 16, 18 and 20. Maximum stimulation occurred on day 20 with 2 mg and 3 mg of hormone, with 88 and 82% increase over controls, respectively. Determination of deoxyribo- and ribo-nucleic acids of mammary glands from lac-tators sacrificed on day 20 revealed no significant increase in DNA but significant increases in RNA after hormone treatment. The data strongly suggest that maximal levels of litter weight size and mammary gland size are limiting in ability to estimate milk secretion potential, while milk yields and RNA values reflect secretory status beyond these limits. Lactogenic hormone at 2 or 3 mg per day stimulates increased lactation more than any other single hormone treatment attempted to date.

Effect of Graded Levels of Insulin on Feed Consumption in Normal Female Rats.

Summary In a group of 24 normal mature female rats weighing 240 g, the mean daily food consumed was 13.3 g and 5.6 g/100 g body weight (bw). During a period of 78 days body weight increased 30 g. Feed consumption/day increased slightly during this period but it was related to increasing bw as shown by a lack of an increase/100 g bw. Mean daily feed intake was determined also in a group of 30 female rats weighing a mean of 242 g. Feed intake was 13.7 g/day and 5.7 g/100 g bw. During 78 days they gained 53 g. As the insulin level was increased daily feed consumption increased up to 20.2 g/day or a 48% increase and 6.9 g/100 g bw, an increase of 21%. This indicates that insulin increased feed intake in excess of the feed required for the gain in weight. All rats survived insulin at 3 unit level. As the insulin was increased further, an increasing number of rats failed to survive and at the 6 unit level only 10 rats survived.

Effect of pregnancy on feed consumption and mammary gland growth in rats.

Summary Normal voluntary food intake of 18 rats was determined prior to and during pregnancy. Before conception the rats weighing 229 g consumed a mean of 13.88 g/day. During days 1–6 of pregnancy, the rats weighing 262 g consumed 16.80 g/day, an increase of 21%. During days 7–13 body weight increased to 279 g and food consumption to 18.47 g/day, an increase of 33%, and during days 14–20 body weight increased to 318 g and food consumption to 21.07 g/day, an increase of 52%. Between days 1 and 20 of pregnancy, food consumption increased a highly significant 70%. During pregnancy the dams increased 104 g; of this 60 g was due to fetal growth and 44 g to an increased weight of the dams. The control group increased only 6 g during 20 days.

Effect of Insulin upon Thyroxine Secretion Rate of Female Rats.

Summary A group of 47 virgin female rats had a mean TSR of 0.99 ± 0.03 μg/100 g bw/day. The 23 rats treated with 3 units of insulin for 10 days prior to and during the period of estimation had a mean TSR of 1.22 ± 0.06 μg/100 g bw/day, significant increase of 20% over the previous TSR of the same animals. In a second group (II), insulin was injected for 10 days, then withdrawn during the 8 to 14 days required to determine TSR. In this group, the increased TSR observed in Group I was maintained.

EFFECT OF GRADED LEVELS OF INSULIN ON LACTATION IN THE RAT.

Summary The daily subcutaneous injection of 3 units of protamine zinc insulin into Sprague-Dawley-Rolfsmeyer lactating rats from day 7 to 19 stimulated highly significant increases in milk yield in comparison with the control group. On day 14 milk yield was increased 38%, on day 16, 25%, on day 18, 26%, and on day 20, 79%. The increase in mean litter weight in comparison with the controls was not significant. The mammary glands as measured by DNA were not significantly increased on day 20 by insulin.