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Biomedical subjects

C H Knight

Publications and source records attributed to C H Knight.

79 records · Page 5Linked to original sources
PubMed1982

Effects of fasting during mid pregnancy or early lactation on mammary development and milk yield in mice.

Mice were fasted during pregnancy or early lactation and the effects on mammary development and milk yield studied on d 13 and d 18 of pregnancy and on d 7 of lactation. Fasting during pregnancy reduced body weight and mammary weight on d 13 of pregnancy but not on d 18. Mammary concentrations and total contents of DNA and RNA ([DNA], [RNA], DNAt, RNAt) were increased or unchanged on d 13 but significantly decreased on d 18. Fasting had no effect on fetal number or weight at either stage of pregnancy. Fasting on d 1 of lactation reduced mammary weight, DNAt and RNAt (but not [DNA] or [RNA]) and the incorporation of tritiated thymidine into DNA or d 2 of lactation. Mammary gland weight and composition on d 7 of lactation were not significantly affected by fasting for 24 h on d 1 of lactation or for 40 h on d 11-13 of pregnancy, except that DNAt was decreased slightly by the latter treatment. Milk yield (litter weight gain) was depressed markedly during fasting on d 1 of lactation, but thereafter recovered so that it was the same as controls between d 3 and 13 of lactation; after d 13 it fell once more. A 40 h fast on d 11-13 of pregnancy had no effect on milk yield. Thus, although normal mammary development was inhibited by starvation, the gland was subsequently able to compensate so that milk yield was not reduced.

Animals↗
PubMed1982

Mammary development in mice: effects of hemihysterectomy in pregnancy and of litter size post partum.

1. Mice were hemihysterectomized on day 8 of pregnancy to reduce the number of feto-placental units.2. Fetal mortality was not affected by hemihysterectomy; mean single-pup weight at birth was increased when compared with sham-operated controls.3. Pregnant sham-operated and hemihysterectomized animals were killed on days 13 and 18 of gestation, and their mammary glands were analysed for total DNA (DNA(t)) and RNA (RNA(t)). Both were significantly lower in the hemihysterectomized group on day 18, but not on day 13.4 Milk yield was assessed, by daily weighing of the litter, in groups of sham-operated and hemihysterectomized lactating animals suckling nine pups each. There was no difference in yield between the two groups.5. One group of sham-operated mice suckling nine pups, one of hemihysterectomized mice suckling nine pups and one of hemihysterectomized mice suckling four pups were killed on day 5 of lactation for mammary gland analysis. There was no significant difference in mammary weight or DNA(t) between the sham-operated and hemihysterectomized animals suckling nine pups, although RNA(t) was still reduced in the latter. Mammary weight, DNA(t) and RNA(t) were all significantly lower in the hemihysterectomized group suckling four pups than in either of the other two groups.6. It is concluded that the less well developed mammary glands of mice which give birth to small litters are capable of compensatory growth during the first few days of lactation if a sufficiently strong suckling stimulus is given.7. It is suggested that control of mammary development by the fetus during gestation and by the suckling young during early lactation are both mechanisms designed to ensure that milk yield is appropriate to the needs of the young.

Animals↗
PubMed1979

Adaptive hyperplasia and compensatory growth in the salt glands of ducks and geese.

1. The incorporation of [3H]thymidine into salt-gland DNA has been studied in vivo and in vitro during adaptation of birds to salt water. 2. No increase in [3H]thymidine incorporation in vivo was apparent in birds on salt water for 0.25 and 1 day compared with those on fresh water. However, by 2 days there was a marked increase. At 7 and 14 days, incorporation was again low but by these later stages the DNA content of the glands was significantly increased. 3. Increased incorporation of [3H]thymidine was also evident in salt-gland slices incubated in vitro from birds on salt water for 2 or 4 days, but not for 14 days, compared with those on fresh water. 4. It is concluded that hyperplasia, as well as the hypertrophy demonstrated previously, occurs as part of the over-all adaptive response of the salt glands during the continual ingestion of salt water, but that the time course of the two processes is different. 5. In geese with one salt gland removed, no indication of compensatory growth of the remaining gland was evident in birds kept on fresh water for 24 days. In such birds on salt water for 14 days, some compensatory growth occurred but, as judged by measurements of DNA, RNA and protein, this could be ascribed to hypertrophy.

Adaptation, Physiological↗
PubMedDate not supplied

Biopsy of the bovine mammary gland.

A technique is described for biopsy of the bovine udder, employing sedation and local anaesthesia. Tissue samples of approximately 5 g were obtained by electrocautery from two quarters of the udder of a cow laterally recumbent. Care was taken to ensure complete haemostasis which was achieved by electrocoagulation and ligation. Postoperative recovery was rapid, and loss of yield was no greater in biopsied glands than in control glands of the same cow. Yield from all quarters returned to preoperative levels within 48 h.

Anesthesia, Local↗