THE MAINTENANCE OF LACTATION IN THE RAT AFTER HYPOPHYSIAL ANTERIOR LOBECTOMY DURING PREGNANCY

1961 ◽  
Vol 22 (4) ◽  
pp. 403-408 ◽  
Author(s):  
A. T. COWIE ◽  
J. S. TINDAL
Keyword(s):  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Anterior Lobe ◽  
Milk Secretion ◽  
Adrenocorticotrophic Hormone ◽  
Milk Ejection ◽  
Growth Indices ◽  
Partial Restoration ◽  
Hypophysectomized Rats ◽  
Milk Ejection Reflex

SUMMARY Experiments to determine the pituitary hormones necessary for the maintenance of lactation in the rat in the absence of either the anterior lobe of the pituitary or the entire pituitary are described. The anterior pituitary or the whole of the pituitary was removed on the 12th day of pregnancy and prolactin (25 i.u. twice daily) plus adrenocorticotrophic hormone (ACTH) (2 i.u./day) was given to the animals from parturition to the 10th day of lactation inclusive. The lactational performances of the two operated groups of rats, as judged by the litter-growth indices, were 53% (anterior lobectomy) and 43% (hypophysectomy) of normal. The milk-ejection reflex was completely restored in the anterior-lobectomized rats by the time of parturition, but the hypophysectomized rats required a further 2 days before milk ejection appeared to be normal. Our experiments confirm that prolactin and ACTH are two important factors in the maintenance of milk secretion in the rat. Since only partial restoration was achieved, however, it is clear that other factors, presumably of anterior-pituitary origin, are required for the full restoration of lactation.

The pituitary and the maintenance of milk secretion

1958 ◽  
Vol 149 (936) ◽  
pp. 330-336 ◽  
Keyword(s):  
Anterior Pituitary ◽  
Causal Factor ◽  
Complete Inhibition ◽  
Posterior Pituitary ◽  
Milk Secretion ◽  
Milk Ejection ◽  
Complete Cessation ◽  
Lack Of Information ◽  
Milk Ejection Reflex

Following the demonstration by Strieker & Grüter (1928) of the lactogenic effects of anterior-pituitary extracts, the importance of the role of the pituitary in maintaining lactation was further emphasized by observations that removal of the pituitary in the lactating animal resulted in a rapid and complete cessation of lactation (for references, see Folley 1952). For a time it was generally assumed that the loss of the anterior pituitary was the causal factor in the cessation of lactation, but when the role of the posterior pituitary in milk ejection was established it became obvious that interference with the milk-ejection reflex could well be the cause of the failure of lactation after hypophysectomy. It therefore seemed desirable to repeat some of the earlier studies on the effect of hypophysectomy on lactation, in order to determine whether the restoration of milk-ejection by the regular administration of oxytocin would affect the results and possibly allow us to distinguish a failure of milk ejection from a failure of milk secretion. In this connexion it may be noted that reports on the maintenance of lactation after hypophysectomy, by administering anterior-pituitary preparations, have been remarkably few, and this lack of information possibly reflects the unsuccessful outcome of attempts which may have failed because milk ejection was not restored. At Shinfield we have studied the effect of hypophysectomy in the lactating rat, both in the presence and absence of adequate oxytocin therapy, and have confirmed that hypophysectomy results in a rapid and complete inhibition of milk secretion (see Cowie 1957), and there seems to be no reason to doubt that this will also be true for other species.

NEUROHUMORAL CONTROL OF THE RELEASE OF ADRENOCORTICOTROPHIC HORMONE

1956 ◽  
Vol 13 (3) ◽  
pp. 229-234 ◽  
Author(s):  
L. MARTINI ◽  
A. de POLI
Keyword(s):  
Ascorbic Acid ◽  
Intraperitoneal Injection ◽  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Portal System ◽  
Posterior Pituitary ◽  
Adrenocorticotrophic Hormone ◽  
Hypophysectomized Rats ◽  
Neurohumoral Control ◽  
Hypophysial Portal

SUMMARY In normal rats intraperitoneal injection of posterior pituitary hormones produces a significant fall in the number of circulating eosinophils and in adrenal ascorbic acid. These effects do not occur in hypophysectomized animals. In hypophysectomized rats bearing hypophysial transplants in the anterior chamber of the eye, both intraperitoneal injection of posterior pituitary hormones and their local application to the eye containing the pituitary graft, also significantly reduce the number of eosinophils and the amount of ascorbic acid in the adrenals. These results are consistent with the hypothesis that the posterior pituitary hormones act as humoral transmitting agents which, released by the hypothalamus into the hypophysial portal system, can activate the anterior pituitary to discharge ACTH.

THE PREPARATION OF SHEEP GROWTH HORMONE

1963 ◽  
Vol 26 (2) ◽  
pp. 259-263 ◽  
Author(s):  
A. L. C. WALLACE ◽  
K. A. FERGUSON
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Deae Cellulose ◽  
Pituitary Hormones ◽  
Starch Gel Electrophoresis ◽  
Epiphysial Cartilage ◽  
Pituitary Glands ◽  
Hypophysectomized Rats ◽  
Starch Gel ◽  
Main Components

SUMMARY Growth hormone has been prepared from sheep pituitary glands by chromatography of a simple buffer extract on DEAE-cellulose. The preparation appears to be free of other anterior pituitary hormones but shows two main components when analysed by starch gel electrophoresis. These components appear similar to those present in standard preparations of ox growth hormone. Sheep growth hormone prepared by this method is not significantly less active than purified ox growth hormone when compared by the tibial-epiphysial cartilage response in hypophysectomized rats.

THE EFFECT OF ANAESTHESIA ON MILK YIELD AND MAINTENANCE OF LACTATION IN THE GOAT AND RAT

1965 ◽  
Vol 33 (3) ◽  
pp. 341-351 ◽  
Author(s):  
A. YOKOYAMA ◽  
K. ÔTA
Keyword(s):  
Control Period ◽  
Experimental Period ◽  
Pituitary Hormones ◽  
The Body ◽  
Final Conclusion ◽  
Milk Secretion ◽  
Milk Ejection ◽  
Once Daily ◽  
Litter Weight ◽  
Subnormal Level

SUMMARY The effect of anaesthesia on lactation was studied in the lactating goat and the lactating rat. Cyclopropane was used in the goat. All goats were milked once daily in the morning. The experimental and the control periods started on Monday and ended on Saturday; the control period was usually followed immediately by the experimental period. Average milk yields in eight experimental periods in three goats ranged from 91·4 to 108·3%, with a mean of 101·4±1·84% (s.e.) of those in the corresponding control periods. The increase in intramammary pressure, which occurred 30–40 sec. after the start of milking of the contralateral teat in the normal lactating goat, was not observed during milking under anaesthesia. Lactating rats were anaesthetized with sodium pentobarbitone. Six or eight pups were placed with the mother to suckle the teat for 2 hr. in the morning. This suckling regime was continued for 5 days. No increase in the body weight of litters was obtained when the litter suckled under anaesthesia. When oxytocin was injected into the anaesthetized mother, a gain in litter weight was observed during the experimental period, although it was smaller than in the controls. In conclusion, a species specificity in the importance of the milk ejection response for the removal of milk has been demonstrated. The fact that milk secretion continued normally in the goat milked under the anaesthesia suggests that the secretion of the pituitary hormones concerned with the maintenance of milk secretion continues in the absence of the milking stimulus. In the rat, although milk secretion was maintained at a subnormal level by oxytocin replacement under anaesthesia, it was not possible to draw a final conclusion as to whether the suckling stimulus is dispensable for the maintenance of milk secretion.

THE RETICULO—HYPOTHALAMIC PATHWAY CONTROLLING THE RELEASE OF OXYTOCIN IN THE EWE

1972 ◽  
Vol 53 (1) ◽  
pp. 71-83 ◽  
Author(s):  
Ph. RICHARD
Keyword(s):  
Medial Forebrain Bundle ◽  
Mesencephalic Reticular Formation ◽  
Milk Secretion ◽  
Milk Ejection ◽  
Small Areas ◽  
Specific Effects ◽  
The Central Nervous System ◽  
Milk Ejection Reflex ◽  
Electrical Activities ◽  
Vaginal Stimulation

SUMMARY The pathways of the milk-ejection reflex in the ewe have been described at the spinal and mesencephalic levels (Richard, 1970; Richard, Urban & Denamur, 1970). The present paper describes the pathways followed by impulses of mammary and vaginal origin between the mesencephalic reticular formation and the neurohypophysis. In the anaesthetized ewe the thalamus is not necessary for the transfer of impulses to the neurohypophysis as shown by studying the electrical activities evoked in the pituitary stalk by mammary or vaginal stimulation. These impulses follow a subthalamic pathway through the medial forebrain bundle. In conscious ewes small areas of coagulations in the pathways did not block the milk-ejection reflex during milking because the fibres are diffuse at all levels of the central nervous system. Larger lesions result in non-specific effects which interrupt milk secretion. Supra-diencephalic structures are not necessary for the milk-ejection reflex.

THE MAINTENANCE OF LACTATION IN THE GOAT AFTER HYPOPHYSECTOMY

1961 ◽  
Vol 23 (1) ◽  
pp. 79-96 ◽  
Author(s):  
A. T. COWIE ◽  
J. S. TINDAL
Keyword(s):  
Anterior Pituitary ◽  
Systemic Treatment ◽  
Pituitary Hormones ◽  
Relative Importance ◽  
Milk Secretion ◽  
Pituitary Extract ◽  
Systemic Injection ◽  
The Right ◽  
Daily Milk Yield ◽  
Daily Milk

SUMMARY Five adult goats were hypophysectomized during lactation; within 10 days their milk yields dropped to a fifth or less of the preoperative levels. The daily milk yield of one of these goats was increased from 10 to 288 ml. by giving daily injections of ox anterior-pituitary extract; the yield of a second goat was increased from 110 to 1315 ml. by daily injections of sheep anterior-pituitary extract. Treatment of the three other goats with purified anterior-pituitary hormones, corticoids, insulin and triiodo-l-thyronine increased their milk yields from 230, 10 and 45 ml./day to 1480, 1320 and 270 ml./day, respectively. Milk secretion was induced in the right udder-half of a sixth animal—which had been hypophysectomized in mid-pregnancy and had aborted—by the local injection of prolactin into the parenchyma of the right udder-half plus the systemic injection of somatotrophin; general lactation was subsequently induced and maintained by systemic treatment with prolactin, somatotrophin, adrenocorticotrophin, corticoids, insulin and triiodo-l-thyronine. The maximum daily yield of the animal was 625 ml. Prolactin and somatotrophin appear to be major components of the lactogenic and galactopoietic complexes in the goat, but further study is required to determine their relative importance and to confirm a preliminary observation that lactation may proceed in the hypophysectomized goat at least for a time by treatment with hormone combinations which include somatotrophin but not prolactin. A marked increase in water intake of one hypophysectomized goat appeared to be associated with the administration of somatotrophin. The possibility of species specificities existing in relation to prolactin are discussed.

PITUITARY GRAFTS AND MILK SECRETION IN HYPOPHYSECTOMIZED RATS

1960 ◽  
Vol 21 (1) ◽  
pp. 115-123 ◽  
Author(s):  
A. T. COWIE ◽  
J. S. TINDAL ◽  
G. K. BENSON
Keyword(s):  
Anterior Chamber ◽  
Antidiuretic Hormone ◽  
Milk Yield ◽  
Milk Secretion ◽  
Milk Ejection ◽  
Kidney Capsule ◽  
Pituitary Tissue ◽  
Hypophysectomized Rats

SUMMARY Lactating rats were implanted under the kidney capsule or in the anterior chamber of the eye with pituitary tissue obtained from their 7–8-day-old sucklings. These rats were again mated and were hypophysectomized on the 4th day of their second lactation. Injections of oxytocin were given thrice daily to induce milk ejection. In such rats the pituitary grafts under the kidney capsule gave a slight temporary maintenance of milk secretion. Substantial increases in the amount of milk and in the duration of milk secretion were obtained when the grafted animals were given daily injections of adrenocorticotrophin. The administration of antidiuretic hormone failed to increase significantly the milk yield of grafted animals. These observations are consistent with the view that such pituitary grafts secrete prolactin.

THE MAINTENANCE OF LACTATION IN THE RAT AFTER HYPOPHYSECTOMY

1957 ◽  
Vol 16 (2) ◽  
pp. 135-147 ◽  
Author(s):  
A. T. COWIE
Keyword(s):  
Growth Hormone ◽  
Replacement Therapy ◽  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Synergistic Action ◽  
Milk Secretion ◽  
Once Daily ◽  
Pituitary Tissue ◽  
Calorie Content ◽  
Rat Pituitary

SUMMARY Attempts to maintain lactation in rats, hypophysectomized on the 4th day of lactation, with extracts of ox and rat pituitary and various purified anterior-pituitary hormones (prolactin, growth hormone (GH), adrenocorticotrophin (ACTH)), singly and in various combinations, are described. Slight replacement effects were seen with pituitary extracts and with prolactin alone (25 i.u. twice daily). Higher milk yields (about 25% of normal) were obtained with a larger dose of prolactin (50 i.u. twice daily). ACTH and/or GH in combination with the lower dose of prolactin (25 i.u. twice daily) enhanced the replacement value of prolactin, but no such synergistic action was seen when they were combined with the higher dose (50 i.u. twice daily). Neither ACTH nor GH, when administered alone, had any replacement value, although a slight replacement was obtained when they were administered together. Intermedin alone failed to maintain lactation. In no case was complete maintenance of lactation achieved, although yields of almost half the normal were obtained in two rats receiving prolactin (25 i.u. twice daily) and ACTH (4 i.u. once daily). No evidence of gross changes in the calorie content of the milk during replacement therapy was obtained. The difficulties of assessing the degree of maintenance of milk secretion and the possible significance of fragments of anterior-pituitary tissue remaining after hypophysectomy are discussed.

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