Acid Content Of Mammary Glands Research Articles

Growth and Biochemical Changes in Mammary Glands of Ewes from 1 to 18 Months of Age

Growth and development of the mammary gland of ewe lambs was characterized by changes of various biochemical constituents. Mammary glands were removed from 49 ewe lambs ranging between 1 and 18 mo of age, weighed before and after trimming, and samples of the trimmed glands were fat extracted and dried. The dried fat-free tissues were weighed, ground, and analyzed for nucleic acids, nitrogen, sodium, potassium, and chloride contents. Fresh samples were used for glycogen determination. Trimmed weight of mammary glands increased rapidly after the 9th mo of age. The pattern was similar for nucleic acid content of mammary glands. Dry matter and fat contents of mammary glands increased up to the 9th mo, fat decreased thereafter, and dry matter remained constant. Protein content was low up to the 9th mo and increased there-after. Sodium and glycogen content in mammary glands increased, but potassium decreased linearly from 1 to 18 mo of age. Allometric growth of mammary tissue started at about 3 mo of age, before onset of puberty at 8 mo of age, but intense mammary metabolic activity started only after the ewe attained puberty.

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

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.

Potentiation of Effect of Prolactin by Adrenocorticotropic and Growth Hormones Upon Weight and Nucleic Acids Contents of Female Rat Mammary Gland

Effects of prolactin, adrenocorticotropic hormone, growth hormone, adrenalectomy, adrenalectomy and corticoids, and adrenalectomy plus prolactin or growth hormone upon the adult female rat mammary gland were investigated.Endogenous hormone effects were studied in rats bearing a transplantable pituitary mammotropic tumor which secretes large quantities of adrenocorticotropic hormone and prolactin. In 40 days the tumor produced a 380% weight increase and 460% increase in deoxyribonucleic acid content of mammary glands in intact rats in contrast to 95% and 297% increase in adrenalectomized rats (10 days after the rats were adrenalectomized). Inhibitory effects of adrenalectomy were prevented by administration of hydrocorticosterone but not by deoxycorticosterone. Administration of growth hormone elicited an increase in gland weight and deoxyribonucleic acid content (70% and 110%) in intact tumor bearing females but not in adrenalectomized animals (—50% and —10%).Prolactin produced mammogenic effects in normal adrenalectomized female rats. Adrenocorticotropic hormone or growth hormone administered separately did not produce any noticeable change in the mammary gland, but effects of prolactin on mammary gland weight and deoxyribonucleic acid content were greatly potentiated by simultaneous injections of adrenocorticotropic hormone and/or growth hormone.

Nucleic Acid Content of Mammary Glands of Virgin and Pregnant Gilts

Six Yorkshire×Hampshire crossbred gilts were slaughtered at second estrus, 25, 50, or 100 days of gestation. Mammary systems were removed immediately and dissected into glands free of skin, muscle, and fat. Growth of the mammary gland was assessed by measuring the weight of the lyophilized fat free tissue, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) contents. The data were analyzed as DNA or RNA concentration per mg of tissue and content per gland.Lyophilized fat free tissue in the mammary system increased 6.5 times during the first 100 days of pregnancy. Average DNA per gland increased 4.9 times during this same period, from 121 mg/gland to 580 mg/gland and RNA increased from 199mg to 1,178mg. Ribonucleic acid and DNA ratio also increased from 1.6 to 2.0 as gestation advanced to 100 days. The increases in lyophilized fat free tissue, DNA and RNA came in the last half of pregnancy and accounted for approximately 100% of the growth.

マウス乳腺の核酸とくにリボ核酸量におよぼす選抜近交の効果

マウス乳腺の核酸とくにリボ核酸量におよぼす選抜近交の効果

Mammary Development and Pituitary Prolactin Level of Heifers from Birth through Puberty and during the Estrous Cycle

Nucleic acid, hydroxyproline (collagen), and lipid content of mammary glands of Holstein heifers from birth to 12 months of age and on Days 0 (estrus), 2, 4, 7, 11, 18, and 20 of the estrous cycle were determined and their relationships to pituitary prolactin were studied. Deoxyribonucleic acid content of the mammary gland increased 1.6 times faster (P<0.01) than body weight between birth and two months of age. The comparable value increased (P<0.01) to 3.5 between five and nine months and then decreased to 1.5 from nine to twelve months of age. During the estrous cycle mammary deoxyribonucleic acid increased 118% (P<0.05) between Day 20 and the day of estrus but declined thereafter. All other mammary constituents measured followed similar patterns of change. Thus, mammary glands of heifers were stimulated to grow at an accelerated rate well in advance of first estrus and following the initiation of estrous cycles most growth occurred during estrus. Pituitary prolactin concentration increased 333% between birth and three months and was maximum at nine months, synchronizing with similar changes in mammary development. The greatest sustained levels of prolactin in the pituitary occurred within three days before ovulation, whereas minimal levels occurred around the time of ovulation.

Intensive nursing and lactational performance during extended lactation.

SummaryIntensive nursing (6 pups/6 intact abdominal-inguinal mammary glands, and replacing all 16-day-old litters every 4 days with 12-day-old foster litters) failed to prevent significant declines in mammary DNA, RNA, and litter weight gains between days 20 and 36 of lactation. But no comparable changes in lactic acid content of mammary glands were observed. Intense nursing maintained pituitary prolactin during extended lactation but ACTH decreased 67.6%. Thus, ACTH may be rate limiting to milk synthesis during extended lactation.

マウス乳腺の核酸とくにリボ核酸量に及ぼす選抜近交の効果

CFW系マウスの乳腺リボ核酸量で選抜を行なうに当り,選抜時期の選定のため泌乳10～16日令間の核酸含量の諸変化を検討した.その結果として,1) 全体的に日令内の分散が大きかつたため,諸測定値の日令間に有意差のないもめが多かつた.2) 総DNA,総RNAは泌乳10～16日の間に退下の傾向があり,RBA/DNAは上昇している.これから乳腺組織は全体としてはやや萎縮し始めたが,個々の乳腺細胞の乳汁分泌能力は増加しているものと考えられる.3) 総DNAと脱脂乾燥乳腺重の相関係数には有意性がなかつた.4) 各日令内の分散は12日令が最も小さい.5) RNA/DNAと子体重増加曲線が平行しており,RNA/DNAと子体重増間にはかなり高い相関(0.45)があつた.日令差を除いた偏相関でも0.41の偏相関係数がありずいれも統計的に有意であつた.RNA/DNAが泌乳能力を代表出来るものと考えられる.6) 従つて,泌乳能力を高めるためにはRNA総量,DNA総量,RNA/DNAが共通的に高いこと,また環境の影響が最も少ないと考えられることから選抜は12日令のRNA/DNA比の値をもつて行なうことが望ましいと考えられる.

NUCLEIC ACID CONTENT OF MAMMARY GLANDS OF LACTATING RATS SIMULTANEOUSLY PREGNANT.

SummaryConcurrent pregnancy significantly enhanced mammary DNA and RNA in rats lactating 18 days when compared with non-pregnant rats lactating 18 days, but the RNA/DNA ratio was not changed. Concurrent pregnancy in rats lactating 21, 24, and 28 days produced, respectively, no change, significant decrease, and no change in nucleic acid content when compared with lactating, non-pregnant rats. Within days 24 and 28 of lactation, nucleic acid content decreased markedly with advancing pregnancy.Standardization of gestation length showed that glands of rats with 7 or more fetuses contained highly significantly less DNA and RNA than glands of lactating, non-pregnant rats.

Nucleic acid content of mammary glands of rats lactating 41 and 61 days.

DNA content of mammary glands of rats lactating 41 or 61 days was not significantly different from that of glands of rats lactating 21 days (10.56 mg and 10.94 mg vs 11.03 mg). RNA content of mammary glands of rats lactating 41 or 61 days was highly significantly less than that of glands of rats lactating 21 days (49.76 mg and 44.83 mg vs 75.06 mg). Similarly, body weight gains of foster litters were less than those of original litters.

Nucleic acid content of mammary glands of pregnant rats.

Total DNA of rat mammary glands per 100 g of body weight increased from 2.77 mg to 7.89 mg during pregnancy, a 184.8% increase, and total DNA increased from 4.76 mg to 17.19 mg, a 261.1% increase. Total RNA increased from 3.06 mg to 15.44 mg during pregnancy and these increases paralleled those of total DNA. RNA/DNA ratio increased from 0.64 to 0.90 as gestation advanced.

Nucleic acid content of mammary glands of lactating rats.

Total mammary DNA per 100 g of body weight increased 9.8% from day 20 of pregnancy to day 1 of lactation and 25.9% from day 1 to day 4 of lactation. Ovariectomy on day of parturition had no influence on mammary hyperplasia during early lactation. On the basis of total DNA per 100 g of body weight maximum mammary development occurred on day 8 of lactation (11.51 mg) and 24.8% of mammary growth occurred during lactation. No significant decrease occurred in mammary DNA until after day 24 of lactation. With the onset of lactation total mammary RNA increased much more rapidly than did total mammary DNA. Maximum mammary RNA content was observed on day 21 of lactation (75.06 mg) after which it declined precipitously to day 28 of lactation (39.61 mg). Mammary gland RNA/DNA ratio increased rapidly when lactation was initiated (1.24), attained its maximum on day 21 of lactation (2.95) and then decreased to day 28 of lactation (1.96). It is suggested that RNA/DNA ratios, when plotted against stage of lactation, represent the normal lactation curve of the rat.