RESUMPTION OF LACTATION BY SUCKLING IN LACTATING RATS AFTER REMOVAL OF LITTERS

1965 ◽  
Vol 33 (2) ◽  
pp. 185-194 ◽  
Author(s):  
K. ÔTA ◽  
A. YOKOYAMA
Keyword(s):  
Mammary Gland ◽  
Nucleic Acid ◽  
Acid Content ◽  
The Other ◽  
Tissue Structure ◽  
Nucleic Acid Content ◽  
Milk Secretion ◽  
Glandular Tissue ◽  
Other Hand ◽  
Short Period

SUMMARY Foster litters were given to lactating rats whose own litters had been removed 3, 5 or 9 days previously. Lactation was restored in all groups by this re-suckling procedure within a relatively short period. The restoration of lactation became more difficult as the interval between the removal of the original litters and the application of the foster litters increased. Changes in the nucleic acid content of the mammary gland after re-suckling were investigated in the rats whose litters were removed for 3 days before re-suckling. Both the DNAP content of the gland and its weight increased steadily in proportion to the length of the period of re-suckling, so that a fairly constant DNAP concentration was maintained in the tissue. The RNAP content and the RNAP:DNAP ratio, on the other hand, increased abruptly at about the time when milk secretion was initiated by re-suckling. The DNAP content continued to increase even after the onset of restored milk secretion. These results suggest that milk secretion after re-suckling began before full restoration of the tissue structure and that growth of the glandular tissue took place concurrently with milk secretion.

scholarly journals Effect of starvation and refeeding on polyamine concentrations and ornithine decarboxylase antizyme in mammary gland of lactating rats

1983 ◽  
Vol 212 (1) ◽  
pp. 149-153 ◽  
Author(s):  
M E Brosnan ◽  
R Farrell ◽  
H Wilansky ◽  
D H Williamson
Keyword(s):  
Mammary Gland ◽  
Nucleic Acid ◽  
Ornithine Decarboxylase ◽  
Acid Content ◽  
Marked Decrease ◽  
Mammary Glands ◽  
Nucleic Acid Content ◽  
Decarboxylase Activity ◽  
Ornithine Decarboxylase Activity ◽  
Polyamine Content

Starvation caused a marked increase in putrescine content in mammary gland of lactating rats, together with a marked decrease in activity of ornithine decarboxylase and appearance of measurable ornithine decarboxylase antizyme. 2. Refeeding for 5 h caused disappearance of free antizyme and ornithine decarboxylase activity returned to the value in fed animals. Putrescine concentration remained elevated. 3. There was no significant change in nucleic acid content of mammary gland from starved rats, but spermidine and spermine contents increased significantly. 4. Refeeding for 5 h returned the spermidine content of mammary glands to ‘fed’ values, and significantly decreased the content of spermine, although it did not reach control values. Thus changes in polyamine content of mammary gland in starved rats are clearly dissociated from changes in either RNA content or activities of polyamine-synthetic decarboxylases. 5. Starvation caused a fall in the content of spermidine in liver, with no change in spermine content. Refeeding for 5 h returned the spermidine content to ‘fed’ values.

CONTENU EN ACIDES NUCLÉIQUES DE SOUCHES DE TAPHYLOCOQUES PRÉSENTANT DES DIFFÉRENCES D'ANTIGÉNICITÉ ET DE VIRULENCE

1962 ◽  
Vol 8 (6) ◽  
pp. 905-913
Author(s):  
J. de Repentigny ◽  
S. Sonea ◽  
A. Frappier
Keyword(s):  
Nucleic Acid ◽  
Virulence Factors ◽  
Acid Content ◽  
Genetic Factors ◽  
The Other ◽  
Nucleic Acid Content

In this work, which is a first step in a study on the mechanism of virulence in staphylococci in relation to some of their genetic factors, two groups of strains were constituted. One group is made of haemolytic, coagulase-positive, and DNase-positive strains, which are virulent for mice by the intracerebral route, and the other group of non haemolytic, coagulase-negative, and DNase-negative strains, which are avirulent for mice. Results have shown that the pathogenic group of strains, containing virulence factors, has a lower nucleic acid content (% of dry cells) than the non-pathogenic group.The two groups of strains are less differentiated by their nucleic acid content than by their coagulase, haemolysin, and DNase activities. A closer correlation seems to exist between this nucleic acid content, and the virulence for mice, and also the number of precipitating antigens obtained with staphylococcal antitoxin.

EFFECT OF SUCKLING AND OF EXTEROCEPTIVE STIMULATION UPON PROLACTIN RELEASE IN THE RAT DURING LATE LACTATION

1972 ◽  
Vol 52 (1) ◽  
pp. 11-22 ◽  
Author(s):  
F. MENA ◽  
C. E. GROSVENOR
Keyword(s):  
Mammary Gland ◽  
Post Partum ◽  
Mammary Glands ◽  
The Other ◽  
Male Rats ◽  
Milk Secretion ◽  
Suckling Period ◽  
Prolactin Release ◽  
Other Hand ◽  
Rat Pituitary

SUMMARY The results of experiments in which the prolactin in the primiparous rat pituitary was bioassayed suggested that the failure of suckling to release prolactin after 8 h of non-suckling on day 21 post-partum was due to the fact that prolactin had been discharged from the pituitary during the 8-h non-suckling period, presumably by exteroceptive signals emanating from the general environment of the animal room. This was substantiated in other experiments in which prolactin release was assessed indirectly through its stimulatory effects upon milk secretion. In these experiments, the mammary glands of rats maintained continuously in the animal room filled faster on day 21 after complete emptying of the glands by exogenous oxytocin, than did either rats on day 14 post-partum maintained continuously in the animal room or rats isolated in a room without other rats on day 21 post-partum. The glands of the latter two groups of rats could be stimulated to fill faster provided prolactin was injected 4 h before the initial emptying of the glands. The exteroceptive stimuli in the animal room environment that stimulated the release of prolactin in the 21-day post-partum rat apparently emanated at least in part from other lactating rats and/or their litters, since faster mammary gland refilling occurred in isolated 21 day post-partum rats when they were exposed to the presence of lactating rats with their litters for 30 min halfway through the 8-h non-suckling period which preceded the initial emptying of the gland. Exposure to male rats, on the other hand, was totally ineffective. A release of prolactin occurred in response to animal room environmental stimuli in the day 14 primiparous rat provided 13–14 day old foster pups were inserted in place of the mother's own pups on day 7. Thus, the rapidly changing characteristics of the pups from 14 to 21 days of age in some manner is involved in the increasing responsiveness of the exteroceptive mechanism for prolactin release which occurs from day 14 to day 21 post-partum.

EFFECTS OF PROGESTERONE AND PROLACTIN ON THE SECRETORY ACTIVITY AND THE NUCLEIC ACID CONTENT OF THE MAMMARY GLAND OF PREGNANT RABBITS

1972 ◽  
Vol 70 (3) ◽  
pp. 603-618 ◽  
Author(s):  
R. Denamur ◽  
C. Delouis
Keyword(s):  
Mammary Gland ◽  
Nucleic Acid ◽  
Essential Role ◽  
Secretory Activity ◽  
Inhibitory Effect ◽  
Nucleic Acid Content ◽  
Mammary Cells ◽  
Milk Secretion ◽  
Qualitative Properties ◽  
Pregnant Rabbit

ABSTRACT Progesterone injected daily at different stages of pregnancy in the rabbit, reduces or temporarily blocks mammary secretion measured on the 24th day either by the incorporation of [14C] glucose into lactose or by the [12C] lactose content of mammary tissues. Progesterone does not affect the number of mammary cells, as determined by the DNA content of the mammary gland, while the quantity of RNA is only reduced if the hormone is injected from the beginning of pregnancy. These results suggest that progesterone has an inhibitory effect on secretory activity, which mainly takes place during the first two thirds of pregnancy. From day 19, twice daily administration of 12.5 IU of prolactin stimulates milk secretion and increases the content of nucleic acids measured on the 24th day. Progesterone (5 mg twice daily) does not prevent these lactogenic effects, nor does it modify the increase in uncleic acids caused by prolactin treatment. Despite the continued presence of progesterone, prolactin has the same qualitative properties in pregnant rabbits deprived of their gonads or pituitary as it has in intact rabbits. Hence prolactin plays an essential role in the mammogenesis and lactogenesis occurring during pregnancy in the rabbit. In addition, our studies show that ovarian secretions other than progesterone are effective under normal conditions of pregnancy, since the administration of progesterone in ovariectomized pregnant rabbit does not allow normal mammary growth despite the maintenance of pregnancy.

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