Pair Of Mammary Glands Research Articles

Intranipple injection with methylene blue for tracing axillary sentinel lymph nodes in rats: A preliminary feasibility study

Background and purpose: Investigate the feasibility of intranipple injection (INN) of methylene blue dye (MB) for tracing the axillary sentinel lymph node (SLN) in rats, to provide different injection methods for finding SLN injection tracers and offer an experimental basis for specific localization of SLN. Methods: Eleven Sprague-Dawley female rats with body masses of 150-400g. Ten rats were randomly selected to use the third pair of mammary glands as the tracer injection site, and the left side was injected with MB (0.05 mL, 1% concentration) by intracutaneous injection of areola (IAA), while the right side was injected with MB(0.05 mL, 1% concentration) by INN. After 5 minutes, the rats were dislocated and dissected, and the blue-stained SLNs were found and recorded, The effectiveness evaluation was based on the number and rate of detection of SLNs as indicators, and the differences between the indicators of the two injection methods of IAA and INN were compared and analyzed. The safety evaluation was based on whether the nipple showed blood flow disorders and necrosis after MB injection by INN in the remaining 1 rat as the criteria. The data were stored and analyzed using Microsoft Excel and SPSS 25.0 statistical software. Νon-normally distributed measurement data were expressed as M (Q1, Q3) and compared by rank sum test, and count data were expressed as cases or percentages and compared by 2 test. p < 0.05 was considered a statistically significant difference. Results: (i)100% (10/10) detection rate of SLNs by applying MB to both INN and IAA modalities;(ii) median number of SLNs detection was 2.0 (1.0,2.0) vs. 1.5 (1.0,2.0) for INN and IAA, respectively (P=0.66), and the difference was not statistically significant;(iii) No nipple necrosis was observed for 4 consecutive days after INN with MB. Conclusion: Tracer detection of SLNs by INN injection in rats is feasible, and the detection rate of SLNs by INN is the same as that of IAA; there is no significant difference in the median number of detected SLNs between the two injection methods. No nipple necrosis was observed after INN with MB.

Epidemiological Investigation of Canine Mammary Tumors in Mainland China Between 2017 and 2021

Epidemiological studies enable us to analyze disease behavior, define risk factors, and establish fundamental prognostic criteria. This study aimed to determine the epidemiological and clinical characteristics of canine tumors diagnosed during the years 2017–2021. The results showed that canine mammary tumors were the most common tumors, and their relative incidence for 5-years-total was 46.71% (504/1,079), with 48.41% (244/504) of benign, and 51.59% (260/504) of malignant. Pure breeds accounted for 84.13% (424/504) of submissions, and adult female dogs (9–12 years old) were most frequently involved, followed by 5–8-year-old females. Remarkably, 2.58% (13/504) occurred in the male dogs. In addition, a high prevalence of mammary tumors (77.38%, 390/504) was diagnosed in unneutered dogs, and different incidence rates were observed in different regions (Northeast, Southeast, Northwest and Southwest China). For clinical factors, the tumor size ranged from 0.5 to 28 cm, with the 0–5 cm being the most common tumor size (47.82%, 241/504), and malignant tumors (4.33 ± 2.88 cm, mean ± SD) were bigger than benign ones (3.06 ± 1.67 cm, mean ± SD) (p < 0.001). The incidence of single tumor (55.36%, 279/504) was higher than that of multiple tumors in dogs, while the latter had a higher incidence of malignant tumors (74.67%, 168/225). According to this study, we also found that canine mammary tumors were more common in the last two pairs of mammary glands. In addition, multiple linear regression analysis showed that there was linear significant relationship between three independent variables (age, tumor size, and tumor number) and histological properties of canine mammary tumor [(p>|t|) < 0.05]. This is the first retrospective statistical analysis of such a large dataset in China to reveal the link between epidemiological clinical risks and histological diagnosis. It aids in the improvement of the host's knowledge of canine tumor disorders and the early prevention of canine mammary tumors.

Flash Irradiation Inhibits Breast Onset and Spares Radiation-Induced Liver Injury

<h3>Purpose/Objective(s)</h3> To clarify the efficacy of FLASH radiotherapy (FLASH-RT) in inhibiting mammary tumorigenesis and normal tissue sparing. <h3>Materials/Methods</h3> We used a spontaneous mammary tumor model of MMTV-PyMT mice for the study. Prior to the formation of mammary tumor, MMTV-PyMT mice (3–6-week-old) were treated with a single fraction dose of 9-16 Gy FLASH-RT or conventional radiotherapy (CONV-RT) using a mice-applicator designed targeting five pair of mammary glands. Tumor growth was detected by thorough palpation of all 10 mammary glands twice a week. Liver function, H&E staining and TUNEL staining of liver tissues were performed to determine the irradiation-induced liver injury. Inflammatory cytokines of TNF-a, IFN-g, IL-6 and IL-10 in the liver tissue and in the serum on Days 6 (D6), 18 (D18) and 31 days (D31) post-irradiation (IR) were tested by ELISA. DHE staining in frozen sections of tumor tissue and liver tissue at 4 weeks post-IR were performed, respectively. <h3>Results</h3> Median days for first tumor occurrence were 65, 62, 58.5 and 52 days of age, while median days for the involvement of 10th mammary gland were 79, 76, 76 and 63 days of age for FLASH (14-16 Gy), FLASH (9-12 Gy), CONV (9-12 Gy) and Control (0 Gy) groups, respectively. Tumor weight at 12 weeks after birth in FLASH and CONV were significantly lower than controls. On 18 days after IR, serum ALT level was significantly increased in the CONV compared with the samples in FLASH. H&E staining of liver in 7 weeks after 9-12 Gy IR revealed that FLASH caused less histological abnormalities in comparison to the samples from CONV, which was similar to the tissue of control. The number of TUNEL-positive hepatocytes in the FLASH was less than that of the CONV but similar to that of the control. In liver tissue, TNF-a, IFN-g and IL-6 significantly increased in CONV compared with FLASH and control; however, IFN-g and IL-6 also significantly increased in FLASH compared with control, while IL-10 significantly decreased in CONV compared with control. Serum IL-6, IFN-g and TNF-a levels in FLASH did not markedly change on D6, D18 and D31 post-IR compared with control. Serum IL-6, IFN-g and TNF-a levels were elevated on D6 and continuously increased on D18 and D31 in CONV, but began to increase on D6, and then recovered to the control level on D18 or D31 in FLASH. Serum IL-10 levels decreased at D6, D18 and D31 in CONV, but began to decrease at D6, and then recovered to the control level at D18 or D31 in FLASH. FLASH induced reactive oxygen species (ROS) accumulation in the tumor tissue but not in normal tissue; while absence of ROS accumulation in either tumor or normal tissue under CONV. Notably, the ROS level of normal liver tissue did not differ under CONV or FLASH. <h3>Conclusion</h3> We found that mammary tumorigenesis was inhibited by FLASH without significant liver injury compared with CONV-RT. The alteration of serum and liver inflammatory cytokines induced by CONV-RT was mildly altered by FLASH. This unique benefit can by partially explained by the accumulatio of ROS in tumor tissue after FLASH.

Prevalence of malignancy in masses from the mammary gland region of dogs with single or multiple masses.

To determine the prevalence of malignancy in masses from the mammary gland region of dogs with single or multiple masses. 95 female dogs from which mammary gland masses had been excised. Medical records of all female dogs from which mammary gland tissue was submitted to the Angell Animal Medical Center Pathology Department from 2009 through 2014 were reviewed. For each dog, data were obtained on breed, body weight, age, reproductive status, and number, location, and histologic classification of masses. The prevalence of malignancy was compared between dogs with single versus multiple masses and among the 5 pairs of mammary glands. Dogs with single versus multiple masses were also compared with respect to age and reproductive status. Among 161 evaluated masses, 137 (85%) were classified as benign or nonneoplastic and 24 (15%) as malignant. Five of 95 (5%) dogs had masses that were not of mammary gland origin. Age, reproductive status, and quantity of masses (single vs multiple) were not significantly associated with the prevalence of malignancy. The prevalence of malignancy in masses from the fourth (caudal abdominal) mammary gland was significantly lower than that in the other 4 mammary glands combined. Dogs with multiple masses in the mammary gland region were not significantly more likely than dogs with single masses to have a malignancy, suggesting that these 2 groups could be managed similarly. Further studies are needed to evaluate the clinical relevance of the lower prevalence of malignancy in masses from the fourth mammary gland.

Cyclic‐glycine‐proline accelerates mammary involution by promoting apoptosis and inhibiting IGF‐1 function

In rodents, post-lactational involution of mammary glands is characterized by the loss of mammary epithelial cells via apoptosis, which is associated with a decline in the expression of insulin-like growth factor-1 (IGF-1). Overexpression of IGF-1 delays involution by inhibiting apoptosis of epithelial cells and preserving the remaining secretory alveoli. Cyclic-glycine-proline (cGP), a metabolite of IGF-1, normalizes IGF-1 function under pathological conditions by regulating the bioavailability of IGF-1. The present study investigated the effect of cGP on the physiological decline in IGF-1 function during post-lactational mammary involution. Rat dams were gavaged with either cGP (3 mg/kg) or saline once per day from post-natal d8-22. Before collecting tissue on post-natal d23, a pair of mammary glands were sealed on d20 (72 hr-engorgement, thus representative of late-involution) and d22 (24 hr-engorgement, thus representative of mid-involution), while the remaining glands were allowed to involute naturally (early-involution). During early-involution, cGP accelerated the loss of mammary cells through apoptosis, resulting in an earlier clearance of intact secretory alveoli compared with the control group. This coincided with an earlier up-regulation of the cell survival factors, Bcl-xl and IGF-1R, in the early-involution cGP glands compared with the control glands. During late-involution, cGP reduced the bioactivity of IGF-1, which was evident through decreased phosphorylation of IGF-1R in the regressed alveoli. Maternal administration of cGP did not alter milk production and composition during early-, peak-, or late-stage of lactation. These data show that cGP accelerates post-lactational involution by promoting apoptosis and the physiological decline in IGF-1 function.

Prevention of preterm labor by omega-3 polyunsaturated fatty acids (PUFAs)

Canine neonates are born hypogammaglobulinemic, and colostrum is their main source of immunoglobulins. The purpose of this study was to evaluate the immune quality of canine colostrum and its variability both among bitches and among mammary glands. The immune quality was estimated from immunoglobulin G (IgG) concentration (ELISA test). The correlation of IgG concentration with refractometry was evaluated. From a total of 44 bitches from 13 different breeds from a single breeding kennel, samples of colostrum and blood were collected one day after the parturition onset. Colostrum was collected separately from each pair of mammary glands (180 pairs). The mean colostrum IgG concentration in our population was 20.8 ± 8.1 g/L (ranging from 8.0 to 41.7 g/L) with no influence of breed size, litter size, age of dam or serum IgG concentration. Colostrum IgG concentration varied widely among pairs of mammary glands within one bitch (variation coefficient: 42 ± 32.1%). Nevertheless, no single pair of mammary glands was found to produce regularly a secretion of higher quality. No difference in IgG concentration was recorded between anterior and posterior pairs either. The BRIX index and the refractive index were significantly, but moderately correlated with colostrum IgG concentration (r = 0.53 and 0.42, respectively). This study demonstrates a great variability in immune quality of colostrum among bitches and among mammary glands within one bitch. Further studies on the suckling behavior of puppies and on determination of the minimal immune quality of colostrum are required to evaluate their impact of this high variability on neonatal mortality in dogs.

Immunoglobulin G concentration in canine colostrum: Evaluation and variability

Canine neonates are born hypogammaglobulinemic, and colostrum is their main source of immunoglobulins. The purpose of this study was to evaluate the immune quality of canine colostrum and its variability both among bitches and among mammary glands. The immune quality was estimated from immunoglobulin G (IgG) concentration (ELISA test). The correlation of IgG concentration with refractometry was evaluated. From a total of 44 bitches from 13 different breeds from a single breeding kennel, samples of colostrum and blood were collected one day after the parturition onset. Colostrum was collected separately from each pair of mammary glands (180 pairs). The mean colostrum IgG concentration in our population was 20.8±8.1g/L (ranging from 8.0 to 41.7g/L) with no influence of breed size, litter size, age of dam or serum IgG concentration. Colostrum IgG concentration varied widely among pairs of mammary glands within one bitch (variation coefficient: 42±32.1%). Nevertheless, no single pair of mammary glands was found to produce regularly a secretion of higher quality. No difference in IgG concentration was recorded between anterior and posterior pairs either. The BRIX index and the refractive index were significantly, but moderately correlated with colostrum IgG concentration (r=0.53 and 0.42, respectively). This study demonstrates a great variability in immune quality of colostrum among bitches and among mammary glands within one bitch. Further studies on the suckling behavior of puppies and on determination of the minimal immune quality of colostrum are required to evaluate their impact of this high variability on neonatal mortality in dogs.

Efeitos da tibolona sobre o parênquima mamário: estudo experimental

To assess the effect of tibolone on mammary tissue of castrated rats over 3 different periods of time. Sixty virgin female Wistar rats were submitted to oophorectomy. Twenty-one days after surgery, with hypoestrogenism confirmed, the experimental rats were randomly assigned to six groups: Tibolone 1 (n=10) received tibolone 1 mg/day for 23 days, tibolone 2 (n=10) for 59 days and tibolone 3 (n=10) for 118 days. The groups control 1 (n=8), control 2 (n=7) and control 2 (n=10) received distilled water for 23, 59 and 118 days, respectively. After treatment, all six pairs of mammary glands were removed and stained with hematoxylin and eosin (HE) for histological analysis after euthanasia. The histological parameters evaluated were: epithelial cell proliferation and secretory activity. The variables were analyzed statistically, with the level of significance set at 0.05. Histological changes were observed in 20/55 rats, mild epithelial hyperplasia in 7/55, moderate epithelial hyperplasia in 5/55, alveolar-nodular hyperplasia in 7/55, atypia without epithelial proliferation in 1/55, and no cases of severe epithelial hyperplasia were found. Secretory activity was observed in 31/55 rats. The secretory activity was significantly higher in the tibolone groups compared to control at all the time points assessed (p=0,001). The histological changes were did not show significance when the control and tibolone groups were compared. The time of exposure to tibolone did not show significance when the three different periods of evaluation were compared. No relation between histological modification and tibolone treatment was verified after short-, medium- and long-term treatment.

Morfologia da glândula mamária do quati (Nasua nasua)

Nasua nasua é um animal onívoro, encontrado em todo Brasil. A reprodução da espécie ocorre somente uma vez ao ano, na primavera. As fêmeas são matriarcas e amamentam suas crias até os 5 meses de idade, vivem com seus filhotes em bandos de até 30 indivíduos. Para descrição morfológica da glândula mamaria do Nasua nasua foram utilizados seis animais provenientes do Criatório Cientifico (Cecrimpas), Unifeob. Autorizado pelo Ibama (Proc.02027.002322/98-99). Para análise macroscópica um animal foi injetado com látex neoprene, sendo a artéria femoral injetada com látex de cor vermelha e a veia jugular de cor azul. Os demais animais foram fixados em solução aquosa a 10% de formaldeído. Para análise microscópica, fragmentos glandulares foram coletados e submetidos ao processo rotineiro, embebido em parafina e corados com Hematoxilina e Eosina, Picrossírius e Azul de Toluidina. Macroscopicamente foram evidenciados três pares de glândulas mamárias, sendo dois pares posicionados na região abdominal e um par na região inguinal. Microscopicamente, notou-se epitélio de revestimento externo das papilas mamárias, epitélio pavimentoso estratificado queratinizado, o qual seguia por toda glândula de forma irregular. Na entrada do óstio, o epitélio da epiderme era modificado ocorrendo uma transição de epitélio pavimentoso estratificado para um epitélio cúbico no ducto papilar. O parênquima glandular era caracteristicamente túbulo alveolar com células secretoras, evidenciado principalmente no animal lactente. Os resultados macroscópicos e microscópicos assemelham-se aos já descritos nas cadelas (Canis familiaris) e os do Procyon cancrivorus pertencente à mesma família do quati, Família Procyonidae.

Abstract 3707: Early stage inhibition of murine mammary carcinogenesis by ultraviolet radiation.

Abstract Epidemiological studies of geographical variations in breast cancer mortality rates have found increased death rates at higher latitudes in USA and other countries 1. This breast cancer latitudinal gradient is hypothesized to be mediated by ultraviolet radiation (UVR) - produced vitamin D3. We first have tested this latitudinal hypotheses using the well-described C3(1)/Tag transgenic murine mammary carcinogenesis model2. We have found that UVR significantly prolongs palpable tumor - free survival (135±23 vs.118±18 days) and reduces the tumor burden and multiplicity (2.9±1.6 vs. 7.2±2.3 tumors), but does not alter the time between the appearance of the first palpable tumor and death in Tag female mice. Therefore we have focused on the effects of UVR on earlier stage carcinogenesis. Tag transgenic female mice have a time-dependent increase in the incidence of ductal carcinoma in situ (DCIS) - like incidence. Thus, Tag mice develop ductal epithelial atypia in 50% of mice at age 8 wks, with progression to intraepithelial neoplasia (resembling human DCIS) in 70-90% of mice (in at least one gland) at 10-13 wks, and DCIS-like changes and early invasion in 100% of mice at age 14-15 wks. We compared weekly the similarity of histological changes between the pairs of mammary glands and found no significant gland site-to-gland site variations. UVR treatment, 350mJ/cm2 thrice weekly from age 6 wks to 15 wks, reduced both the percentage of DCIS-bearing mice (65, 60, 51, 32 and 20% reduction at week 8, 9, 11, 13 and 14) and the percentage of DCIS-bearing glands in each animal (82, 55, 66, 20 and 19% reduction at week 9, 11, 13, 14 and 15). The mechanism of the UVR-mediated prevention of the murine mammary carcinogenesis is unclear but there is evidence favoring a Hedgehog (HH) signaling-dependent mechanism, since D3 is a potent inhibitor of the HH signaling pathway, which is upregulated in many cancers including breast cancer3-5. Consistent with this idea we found that UVR reduces DCIS-like changes in Ptch+/- mice. Taken together our results support our hypothesis that inhibition of early stage mammary carcinogenesis by UVR-produced vitamin D3 underlies the latitudinal gradient. 1. Garland, F. C. et all. Prev Med 1990, 19, 614-22. 2. Green, J. E. et all. Oncogene 2000, 19, 1020-7. 3. Bijlsma, M. F. et all. PLoS Biol 2006, 4, e232. 4. Moraes, R. C. et all. Development 2009, 136, 1423-32. 5. Lewis, M. T. et all. Development 1999, 126, 5181-93. Citation Format: Anastasia M. Makarova, Grace Wang, Lynn Wang, Joy Wang, Yefim Khaimskiy, Ervin H. Epstein. Early stage inhibition of murine mammary carcinogenesis by ultraviolet radiation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3707. doi:10.1158/1538-7445.AM2013-3707

Relationship between growth of nursing pigs and composition of sow colostrum and milk from anterior and posterior mammary glands

Piglets that nurse anterior mammary glands grow faster than those suckling posterior mammary glands. The underlying mechanisms are not known. The purpose of this study was to investigate if there is a difference in composition in colostrum and milk secreted by anterior and posterior mammary glands. Seven healthy sows were used. The first three pairs of mammary glands were defined as anterior mammary glands (AMG) and the rest as posterior mammary glands (PMG). Additionally, the total of 87 born piglets from 7 litters derived from the sows involved in the experiment was analyzed. Piglets from each litter that nursed AMG were defined as AMG group while the rest of piglets from the litter were defined as PMG group. Colostrum and milk were collected at days 1, 2, 3 and 7 after parturition. Samples taken from anterior and posterior mammary glands were pooled, respectively. Results showed that total protein, IGF-I and insulin concentrations were significantly higher in the colostrum of anterior than posterior glands and IGF-I concentration remained significantly higher in milk of anterior compared to posterior glands. There were no significant differences in fat, dry matter and lactose among anterior and posterior glands during all examined periods. Additionally, blood samples from nursing sows were obtained at days 1 and 7 after parturition. Results showed that concentrations of Ca, glucose, total protein, albumin, globulin, total bilirubin and insulin significantly increased from day 1 to day 7 of parturition while concentrations of P, BUN, CK and IGF-I did not significantly change during this period. Initial body weight of pigs nursing the anterior gland was higher but not significantly that those suckling posterior glands. Pigs that nursed anterior glands gained weight faster then those which suckled posterior glands resulting with significantly higher body weigh of piglets nursing anterior compared to posterior glands at day 8 of neonatal life (p < 0.05). Therefore, it may be concluded that the priority of anterior glands milk secretion in total protein and grow stimulating factors may have an impact on increased body weight gain of nursing pigs.

Estudo morfofuncional das glândulas mamárias de Mão Pelada, Procyon cancrivorus

Para a descrição macro e microscópica das glândulas mamárias foram utilizadas três fêmeas de Mão Pelada (Procyon cancrivorus). As amostras das glândulas foram processadas conforme técnicas rotineiras para histologia. As fêmeas estudadas apresentaram 3 pares de glândulas mamárias, sendo um par de glândula mamária abdominal cranial, um par de abdominal caudal e um par de inguinal. As papilas mamárias apresentaram formato pendular, como os canídeos domésticos. Microscopicamente, a glândula mamária apresentou da porção externa para a interna: epiderme (epitélio estratificado pavimentoso queratinizado), derme (tecido conjuntivo frouxo e tecido conjuntivo denso não modelado), fibras musculares lisas e ductos papilíferos que abrem em vários ósteos papilares em formato de "chuveiro". A porção secretora glandular era caracteristicamente túbulo alveolar, com células cuboidais dispostas em camada simples. Os resultados indicam que o conjunto glandular estudado é semelhante ao da cadela (Cannis familiaris) tanto em seu aspecto macroscópico quanto em seu aspecto microscópico, este fato sugere que podemos utilizar o Mão Pelada e o Cão como modelos similares de estudo, para identificação de patologias relacionadas a este sistema.

Positional variation in the molecular regulation of mammary gland development

Our lab aims to unravel the molecular mechanisms of early mammogenesis, using the five pairs of mammary glands in mouse embryos as a model. We found that loss of Gli3 results in induction of only mammary rudiment pairs #1, #2 and #4, but not #3 and #5. Moreover, the #2 and #4 pairs each have distinct morphogenetic defects, while pair #1 is morphologically normal. Our in vivo approach to rescue all defects by activating a pathway downstream of Gli3 resulted in induction of pair #3 only, but not of pair #5, nor did it restore morphogenesis of pairs #2 and #4. Analysis of the latter two pairs is ongoing. We conclude that all five pairs of mammary rudiments in mice differ in their molecular regulation of induction and early morphogenesis, despite their identical functional outcome. This contrasts with other multiples of the same structures, e.g. somites, limbs or hair follicles, which are generally thought to share the same inductive signals, while unique specification signals establish their anatomical and functional differences such as those between fore‐ and hind limbs. The variation in molecular inductive mechanisms of mammary glands may explain the differences in numbers and positions of mammary glands among mammalian species. It also increases the chances of survival of the species when a gene function is altered.Funding provided by CBCRP:10FB‐0116 and A*STAR.Grant Funding Source: A*STAR

Effects of raloxifene on the mammary epithelium of female rats in persistent estrus

Objective. The aim of this study was to evaluate the morphological and morphometric alterations produced by raloxifene in the mammary epithelium of female rats in persistent estrus.Materials and methods. Twenty-one female Wistar–Hannover rats in persistent estrus induced by 1.25 mg of testosterone propionate were randomly divided into two groups: Group I (n = 10), receiving only water and used as control; Group II (experimental, n = 11), treated with 3 mg of raloxifene daily for 21 days. The first abdominoinguinal pair of mammary glands was extirpated and processed for morphological and morphometric evaluation. The data were statistically analysed using Student's t-test (p < 0.05).Results. Morphology revealed signs of epithelial atrophy, and morphometry showed a significant reduction in the mean number of ducts and alveoli in the experimental group (12.82 ± 0.42 and 2.91 ± 0.53, respectively) when compared with the control group (28.70 ± 1.15 and 7.20 ± 0.57, respectively). This difference was statistically significant, both for the ducts and for the alveoli (p < 0.001).Conclusion. The present results indicate that, at the dose and during the time of treatment used, raloxifene induced atrophy of the mammary epithelium of rats in persistent estrus.

Role of FGF10/FGFR2b signaling during mammary gland development in the mouse embryo.

The mouse develops five pairs of mammary glands that arise during mid-gestation from five pairs of placodes of ectodermal origin. We have investigated the molecular mechanisms of mammary placode development using Lef1 as a marker for the epithelial component of the placode, and mice deficient for Fgf10 or Fgfr2b, both of which fail to develop normal mammary glands. Mammary placode induction involves two different signaling pathways, a FGF10/FGFR2b-dependent pathway for placodes 1, 2, 3 and 5 and a FGF10/FGFR2b-independent pathway for placode 4. Our results also suggest that FGF signaling is involved in the maintenance of mammary bud 4, and that Fgf10 deficient epithelium can undergo branching morphogenesis into the mammary fat pad precursor.

Growth of nursing pigs related to the characteristics of nursed mammary glands.

The purpose of this study was to determine growth performance of nursing pigs in relationship to teat order and to observe teat preference by pigs. In the first experiment, litter size of 13 primiparous sows was adjusted to 9 (8.7 +/- 1.5) pigs and teat order of each litter was observed on the day before slaughter. Another group of eight sows was killed on d 0 (within 12 h after farrowing). In the second experiment, litter size was adjusted to 9 (8.9 +/- 1.4) pigs for 20 primiparous sows and teat order for each litter was observed 1 d before slaughter. The weights of sows and individual pigs were recorded at farrowing, weekly, and on the day before slaughter. Mammary glands were collected at slaughter on d 21 of lactation and trimmed of skin and the extraneous fat pad. Individual glands were separated, weighed, and ground for measurement of dry matter, dry fat-free tissue, protein, fat, ash, and DNA contents. Middle mammary glands had the greatest wet weight among glands obtained within 12 h after weaning (P < .05). For sows completing the 21 d lactation, only glands known to have been nursed were included in the data sets. Greater than 60% of the first four pairs of mammary glands were nursed, and less than 40% of the seventh and eighth glands were nursed by pigs during lactation. Pigs that nursed the first five pairs of anterior glands gained faster than pigs nursing the remaining glands. The first five pairs of anterior glands had greater wet and dry weights, and greater protein and DNA contents compared with the remaining glands. Pigs that nursed heavier glands gained weight faster (r = .68, P = .0001), and those heavier glands contained greater amounts of protein (r = .98, P = .0001) and DNA (r = .66, P = .0001). Variation in weight gain of pigs nursing the anterior and middle glands was not statistically significant. The functional superiority of anterior and middle glands was positively correlated with body weight gain of nursing pigs.

BOTH DIETARY CALORIE AND FAT AFFECT THE GROWTH OF TRANSPLANTED MAMMARY-TUMORS IN RIII/SA MICE - THE EFFECT OF CALORIE IS MORE PROFOUND THAN THE EFFECT OF FAT

The effects of dietary calories and/or fat on the growth of mammary tumor transplants, their expression of mouse mammary tumor virus (MMTV) and the incidence of lung metastasis were examined in RIII/Sa mice. Starting at 3-4 weeks of age, groups of female mice were fed either high isocaloric diets (16 kcal/day/mouse) containing 25% or 5% corn or fish oil or low isocaloric (10 kcal/day/mouse) diets containing 25% or 5% fish or corn oil. After one week, small pieces (2x2x2 mm) of tumor tissue, prepared from a transplantable mammary tumor, were inserted into the fourth pair of mammary glands of mice, and the mice maintained on their respective diets until sacrifice. All mice developed palpable tumors during a period of 3-4 weeks. After 12 weeks, all those mice that were assessed for tumor burden were sacrificed, tumor weight in each mouse determined, and the level of the expression of MMTV in the tumors evaluated by dot blot hybridization. Our results show that low isocalorie diets, regardless of the type or amount of fat, inhibited tumor growth by at least 60% in comparison to high isocalorie diets. However, mice fed low isocaloric diets containing fish oil were also found to produce smaller tumors (20-40%) as opposed to those mice fed similar, but corn oil containing diets. Fatty acid analyses of mammary tumors and liver tissue of mice fed corn oil and fish oil containing diets revealed that while normal and tumor tissues from both groups contained high levels of polyunsaturated fatty acids, the tissues of mice fed corn oil had the n-6, whereas the mice fed fish oil had the n-3 family of fatty acids. The levels of MMTV expression were found to be unaffected by either caloric or fat content in the diet. In a separate set of experiments, the effect of a low calorie diet on lung metastasis was determined, It was found that mice fed a low calorie diet produced significantly less metastatic lung nodules than those mice fed a high calorie diet: the mean survival time for the former group of mice was 106 days, as compared to only 71 days for the latter group of mice. In conclusion, we suggest that the amount of calories in a diet is more important than the amount or the type of fat in suppressing the growth of transplanted tumors and that a low calorie diet may also lower the incidence of lung metastasis.

Melatonin inhibits mammary gland development in female mice.

The objective of this study was to determine whether melatonin (aMT) influences the postnatal development of the mammary gland parenchyma in female mice from the time of weaning to adulthood. Twenty-one-day-old female BALBc mice were treated with daily subcutaneous injections of aMT (200 micrograms) or diluent, 3 hr before the onset of darkness (photoperiod LD 12:12). At 3, 5, 7, 9, 11, and 13 weeks of age, batches of 20 animals (ten controls and ten aMT-treated) were sacrificed and the second pair of mammary glands were dissected to evaluate their degree of development. Melatonin decreased body weight gain from 2 weeks before until 2 weeks after the onset of puberty. Treatment with aMT also resulted in a lower DNA content and smaller area of the mammary gland from the time of puberty until the end of the study. In aMT-treated mice the phase of highly positive allometric growth began 2 weeks later, but ended at the same time as in controls (11th week of life). Finally, aMT decreased the development of terminal, lateral, and alveolar buds while it increased the number of terminal ducts per gland. We conclude that pharmacological doses of aMT (1) reduce body weight gain at the peripuberal age; (2) partially inhibit postnatal mammary gland development by reducing the number of epithelial structures representing sites of growth and increasing that of structures representing the final state of ductal growth in virgin animals; (3) delay the onset of the shorten the phase of rapid mammary growth occurring in early postpuberal age.

Role of hormones on the induction of retinoic acid binding protein in mouse mammary gland organ culture.

Influence of various hormones on the induction of cellular retinoic acid binding protein (CRABP) was investigated in the mouse mammary gland organ cultures. Thoracic pairs of mammary glands from the BALB/c mice were cultured for seven days in the presence of various hormones in CMRL medium at 37 degrees C under 50% O2, 5% CO2 and 45% N2 atmosphere. There was a modest increase of mammary CRABP by insulin (I) + prolactin (P), however, addition of progesterone (Pg) or estrogen (E) + Pg to the medium resulted in a dramatic increase in the CRABP. Aldosterone (A) + hydrocortisone (F), in addition to I + P, which promotes differentiation to an extent similar to that of I + P + E + Pg did not have any influence on the induction of CRABP. These results indicate that prolactin and/or Pg in the medium can increase the concentration of CRABP in the mammary gland in vitro. From the results presented in this report, as well as previous work by other investigators, it is concluded that the biological response to retinoids in the mammary tissues cannot be correlated with the absolute concentration of CRABP in the cells. However, the biological response may be dependent upon both the ability of the target organ cells to metabolize the retinoid and to have minimal concentration of CRABP for binding to the active metabolite. The functional significance of hormone-induced CRABP is presently unknown.

Modification of the mouse mammary gland organ culture technique

A modified procedure for culturing an entire thoracic pair of mammary glands from virgin mice is described. The glands are incubated in CMRL 1066 medium supplemented with hormones in a controlled atmosphere chamber with a gas phase of 50% O2, 5% CO2, and 45% N2 at 37° C.