Gland Development Research Articles

Developmental changes of sugar residues and secretory protein in mucous cells of the early postnatal rat parotid gland

Mucous cells have been identified in the terminal portions of the early postnatal parotid gland in human and rat, although mature parotid gland acini are composed of serous cells or seromucous cells. Previously, Ikeda et al. demonstrated that mucous cells are present in the rat parotid gland on days 1 to 8 after birth and that the secretory granules within these mucous cells share some histochemical characteristics with mature serous cells. However, it is still not clear whether the mucous cells change into serous cells as the gland develops. The purpose of this study was to determine whether the mucous cells that appear in the early postnatal rat parotid gland change into serous cells. Parotid glands were obtained from male or female Wistar rats (aged 0–14 days and adults). Fixed tissue sections were reacted with soybean agglutinin (SBA) and wheat germ agglutinin (WGA) to detect glycoconjugates, or were stained using an anti-neonatal submandibular gland protein B1 (SMG-B1) antibody to identify serous acinar cells. The sections were observed by transmission electron microscopy. Electron microscopy revealed that cells with characteristics intermediate between those of mucous and serous cells (transitional cells) appeared around day 8 and that the nuclei of these cells did not show chromatin condensation, a characteristic of apoptotic cells. Lectin histochemistry showed that the mucous cells had the same sugar residues as the serous cells, which appeared after day 10. Immunohistochemistry with an anti-SMG-B1 antibody gave a positive reaction not only in the cells with highly electron-dense granules but also in the electron-dense cores of bipartite or tripartite granules in the transitional cells. Cells with morphological characteristics intermediate between those of mucous and serous cells (transitional cells) appearing in the early postnatal rat parotid gland begin to produce B1-immunoreactive protein common to serous acinar cells during development of the gland. Anat Rec 255:155–161, 1999. © 1999 Wiley-Liss, Inc.

Regulated expression patterns of IRX-2, an Iroquois-class homeobox gene, in the human breast.

In the mouse mammary gland, homeobox gene expression patterns suggest roles in development and neoplasia. In the human breast, we now identify a family of Iroquois-class (IRX) homeobox genes. One gene, IRX-2, is expressed in discrete epithelial cell lineages being found in ductal and lobular epithelium, but not in myoepithelium. Expression is absent from associated mesenchymal adipose stroma. During gland development, expression is concentrated in terminal end buds and terminal lobules and is reduced in a subset of epithelial cells during lactation. In contrast to observations for many homeobox genes in the mouse mammary gland in which homeobox gene expression is lost on neoplastic progression, IRX-2 expression is maintained in human mammary neoplasias. Data suggest IRX-2 functions in epithelial cell differentiation and demonstrate regulated expression during ductal and lobular proliferation as well as lactation.

Performance and gastro-intestinal response of broiler chickens fed on cereal grain-based foods soaked in water

1. Two experiments were carried out to investigate the addition of 1.3 kg water per kg air-dry mash diets containing high proportions (600 to 700 g/kg) of ground cereal grains (wheat, barley or oats) on broiler performance and the structure and function of the gastro-intestinal tract. 2. Chicks at the age of 7 d were fed on the wheat-, barley- or oats-based diets in the dry or wet forms for 35 d. Food and water intakes were recorded daily while body weight was measured weekly. Two birds from each treatment were killed each week to measure gut size and the viscosity of gut contents. Tissue samples from various digestive segments were histo-morphologically examined to determine the thickness of tissue layers, size of tissue glands, villa heights, crypt depths and thickness of tunica muscularis . Crypt cell proliferation rate (CCPR) for each segment was also determined using a metaphase arrest technique. 3. The results from both experiments showed that wetting food significantly ( P <0.05) increased food intake, total water intake and body weight gain of broiler chickens. The body weight gains of birds were proportional to their food intakes so that the efficiency of food utilisation was similar for all treatments. Dry matter retention of food tended to increase in birds given wet food from 7 to 21 d but not thereafter, compared to the dry-fed birds. Although water intake from the water bottle was significantly ( P <0.05) reduced in birds given wet food, total water intakes from the water bottle plus that from food were significantly ( P <0.05) higher in the wet-fed birds than in the dry-fed birds. The ratio of total water to dry food intake was, however, similar in both feeding regimens. 4. The fresh empty weight of the gut was increased by wet-feeding while its relative weight to body weight and the length of gut was not affected by dietary treatments. Significantly greater development of the tissue glands in the proventriculus and gizzard was observed in the birds given wet food; this was associated with the reduced thickness of the muscular layer of these segments. An increase in villus height was also observed in duodenum, small intestine, caeca and colon of birds given wet food, compared to those given dry food. CCPR was significantly ( P <0.05) reduced by wet-feeding throughout the digestive tract. This was associated with a significant decrease in the mean viscosity of the gut contents and the concentration of volatile fatty acids (VFAs) in the caeca. 5. Wetting diets based on cereal grains caused a significant improvement in the performance of broiler chickens. The mechanism of the beneficial effects of wet feeding could be attributed to the decreased viscosity of gut contents; the greater development of the layer of villi in the digestive segments and the reduced CCPR in the crypts of the epithelium.

Technical note: use of slow-release estradiol and prostaglandin F2alpha to induce pseudopregnancy and control estrus in gilts.

We determined whether a single injection of slow-release estradiol-17beta (SRE2) would induce pseudopregnancy in gilts and whether PGF2alpha would regress the corpora lutea (CL) of pseudopregnancy. Crossbred gilts (n = 40) were induced to ovulate by treatment with 400 IU of hCG + 200 IU of eCG (PG600, Intervet, Millsboro, DE) given at 180 d of age (d = 0). On d 14, gilts were injected i.m. with one of five doses (n = 8 gilts/dose) of SRE2 (0, 12.5, 25, 50, or 100 mg). Blood samples were collected before SRE2 and twice weekly until d 73 to monitor serum progesterone (P4) and estradiol (E2). On d 59, gilts received (i.m.) 10 mg of PGF2alpha (Lutalyse, Pharmacia Upjohn, Kalamazoo, MI) and were checked for estrus for 7 d. On d 62, mammary development was scored (0 = no development; 1 = some development; 2 = teat and gland development) by a neutral observer. Treatment with SRE2 increased (P < .05) peak E2 concentrations, duration of luteal function, and mammary gland score. There were no differences (chi-square, P > .05) among doses of SRE2 in the percentage of pseudopregnant gilts that showed luteolysis after PGF2alpha. We conclude that a single injection of SRE2 can induce pseudopregnancy and that the CL can be regressed with PGF2alpha, providing a simple method for controlling estrus in gilts.

Regulation of mammary gland development by tissue interaction.

Development of the mammary glands is initiated in the embryo but the major part of their development occurs in the adult. While development in puberty and pregnancy is dependent on hormones, prenatal and early postnatal development appear to progress autonomously. Mutual and reciprocal epithelial-mesenchymal interactions are critical for both phases of development. Specific steps such as the formation of the bud, the first appearance of hormone receptors, formation of the primary sprout and ductal elongation have been shown to be governed by epithelial-mesenchymal signaling. In recent years, some of the signaling molecules that are required in these processes have been identified through gene inactivation. We discuss the potential role of these factors in mediating growth and differentiation. In addition we provide evidence that mammary epithelial cells from late embryonic stages are already capable of synthesizing milk proteins when subjected to appropriate hormonal stimulation.

YAC rescue of downless locus mutations in mice.

Mice with mutations at the downless (dl) locus have defects in hair follicle, tooth, sweat gland, preputial gland, Meibomian gland, and tail development. The dl phenotype is analogous to the human genetic disorder termed autosomal hypohidrotic (or anhidrotic) ectodermal dysplasia (HED). On the basis of the identification of two related transgenic insertional mutations in the downless gene, yeast artificial chromosomes (YACs) were identified that map to the critical region of mouse Chromosome (Chr) 10. To determine which of the YACs contain the dl gene, we generated YAC transgenic mice by mouse embryo microinjections. The 200-kb YAC B25.D9 was found to rescue all of the downless defects. In addition, the transgenic YAC rescued the dominant Sleek (Dlslk) allele. Since the sequences within the YAC are entirely deleted in one of the transgenic mutants, our results establish that Sleek encodes a dominant-negative protein whose effects can be reversed by expression of extra copies of the wild-type locus.

Adaptation of hypopharyngeal gland development to the brood status of honeybee ( Apis mellifera L.) colonies

We studied pollen consumption, head weight, hypopharyngeal gland (HPG) acini diameter, and protein synthesis and transfer in honeybee workers reared in colonies with normal and with decreasing amounts of brood. We found that head fresh weight is correlated with size of the glands and that pollen consumption is positively correlated with gland development. An effect of brood on size of the glands could be confirmed, but was not as profound as in previous studies. Similarly, no difference in the amount of protein synthesized or transferred in workers living under the two brood conditions was found. We suspect this is due to the fact that HPGs also supply food to young bees and in our study young bees were always present while in previous studies, colonies often lacked both brood and young bees.

Immunohistochemistry of carbonic anhydrase isozymes VI and II during development of the rat salivary glands.

Secreted carbonic anhydrase (isozyme VI; CA VI) was localized by immunohistochemistry in the developing postnatal rat submandibular and parotid glands using a specific monoclonal antibody to the rat enzyme. CA VI immunostaining was not detectable in the glands before birth. In the submandibular gland, granular immunostaining for CA VI was detectable in several terminal tubule cells of 1-day-old rats. At 1 week, the CA VI-positive cells were located at the periphery of the terminal tubules and appeared to be budding off the tubules. These cellular buds gradually increased, and, by 4 weeks, formed acini. CA VI was also detected in the duct lumen from day 1. The immunostaining in the parotid gland was detected sporadically in the acinar cells at 2 or 3 weeks. By 4 weeks, when the gland was almost indistinguishable from the adult one, the number of positive acinar cells had increased. Their number, however, was far smaller than in the adult gland, and the enzyme could not be detected in the duct lumen. CA II was also localized using specific antibodies to the rat isozyme. CA II was detectable in the inter- and intralobular striated ducts at 2 weeks after birth in the submandibular gland and at 3 weeks in the parotid gland. These results suggest that CA VI is secreted into saliva from soon after birth and that CA II appears in parallel with the functional maturation of the ducts. In addition, CA II was transiently expressed by the cellular buds of the submandibular gland at 2 and 3 weeks.

Correlations of litter size and maternal serum progesterone concentration during pregnancy with mammary gland growth and development indices at parturition in Javanese Thin-Tail sheep

Correlations of litter size and maternal serum progesterone concentration during pregnancy with mammary gland growth and development indices at parturition in Javanese Thin-Tail sheep

Local control of mammary development and function

For the mother, lactation represents the final stage of an investment in her genetic material. Like any investment it is costly and, hence, it needs to be carefully controlled. To her offspring, lactation means survival, so it must happen at any cost. This apparent conflict is rationalized by the mother devolving some control to the offspring while retaining ultimate sanction herself. Part of this results from overt and more subtle influences of the presence of young on the mother's endocrine system, but an equally important part operates at each mammary gland to ensure that output is appropriate to the needs of the young, and no more. The young exert influence by removing milk, while the mother retains control by responding on an hour to hour basis to the presence of milk in the gland. Local control is inevitably most evident where secretion itself is concerned, but also operates to influence lactogenesis, gland development and, eventually, gland involution. This paper will review local control of mammary function, emphasising the important role played by an autocrine inhibitory protein, the feedback inhibitor of lactation.

Bacterial Symbionts Colonize the Accessory Nidamental Gland of the Squid Loligo opalescens via Horizontal Transmission.

The accessory nidamental gland (AN gland), a reproductive organ of the mature female squid Loligo opalescens, harbors a dense culture of bacteria of unknown function. A multilayered sheath surrounding the L. opalescens egg case is similarly colonized by bacteria that presumably originate in the AN gland, as evidenced by their presence in the egg case at oviposition. This study investigates how these bacteria are transmitted to juvenile squid and examines some morphological consequences of bacterial colonization of AN gland tissues. By observing the structure of the AN gland in adults and the development and bacterial colonization of the gland in juveniles raised in captivity, we determined that the AN gland was absent in newly hatched squid and did not appear until 87 days post-hatching. At 129 days posthatching, the organ displayed tubules composed of a single layer of epithelial cells and expressing numerous cilia and microvilli. These tubules were not yet fully formed and thus were open to the mantle cavity and external seawater, possibly to aid in the acquisition of microorganisms. Since the AN gland developed a considerable time after hatching, it most likely acquires its symbionts horizontally from environmental seawater and not vertically from the egg case sheath. The switch from expression of cilia to production of microvilli on the epithelial cell surface may dictate the competence of the tissue for bacterial colonization. Electron microscopic examination of juvenile and adult AN glands revealed that an analogous process occurs during the development of the related light organ of other cephalopod species that harbor symbiotic bacteria.

Spatial and temporal expression pattern of POU-M1/SGF-3 in Bombyx mori embryogenesis.

The expression pattern of the POU-M1/SGF-3 gene during Bombyx embryogenesis has been analysed using in situ hybridization and immunohistochemistry. At the early embryo retraction stage, both the transcripts and protein were first detected in precursor cells of the prothoracic glands in the labial segment, in the oenocytes in the A1-A8 segments and in invaginated regions in the mandibular and maxillary segments. The invaginated regions in the mandibular segment develop into the abductor plates in the lateral anterior region and the adductor plates in the posterior region. From the latter plates, the salivary glands elongate. The invaginated regions in the maxillary segment develop into the corpora allata in the anterior region and the subbuccal glands in the posterior region, which unite with tissues of the anterior region of the mandibular segment at later stages. After the embryo retraction stage, the transcripts and protein products also become detectable in the silk gland invagination points and, after the blastokinesis stage, the products are restricted to the entire anterior silk glands and to the anterior and middle parts of the middle silk glands. Expression can also be detected in a part of the hindgut, in the tracheal system and in some cells of the central nervous system. These results indicate that POU-M1/SGF-3 might play roles in the development of the silk glands, nervous system, tracheal system and other organs like the prothoracic glands and oenocytes.

Postmetamorphic Development of Supernumerary Thyroid Glands in Pleurodeles waltl

Postmetamorphic Development of Supernumerary Thyroid Glands in Pleurodeles waltl

Redistribution of carbonic anhydrase VI expression from ducts to acini during development of ovine parotid and submandibular glands.

Carbonic anhydrase VI (CA VI) is a secreted enzyme produced predominantly by serous acinar cells of submandibular and parotid glands. We have investigated the developmental pattern of CA VI production by these glands in the sheep, from fetal life to adulthood, using immunohistochemistry. Also, a specific radioimmunoassay for CA VI was used to measure changes in enzyme expression in the parotid gland postnatally. CA VI is detectable by immunohistochemistry in parotid excretory ducts from 106 days gestation (term is 145 days), in striated ducts from 138 days and in acinar cells from 1 day postnatal. The duct cell content of CA VI declined as the acinar cell population increased, a feature also of CA VI immunoreactivity in the submandibular gland. Production of CA VI by submandibular duct cells was detectable initially at 125 days gestation, and acinar production was not seen before 29 days post-natal. Apart from the differing ontogeny of CA VI production in ducts and acini of parotid and submandibular glands, there was a parallel pattern of CA VI expression during the development of these major salivary glands. With the development of the acinar tissues in the postnatal lamb, there was a dramatic increase (about 600-fold) in the level of expression of CA VI in the parotid gland between days 7 and 59 as measured by radioimmunoassay.

Developmental changes in mucous cells of the early postnatal rat parotid gland: an ultrastructural and histochemical study.

Previous studies on the development of the parotid gland in various mammals have demonstrated that terminal clusters and acini contain mucous cells during the early postnatal period. However, little information has been available concerning the exact fate of the secretory granules in the mucous cells, specifically as to whether or not the mucous cells differentiate into serous cells. The present study aimed to determine the time of appearance of the mucous cells in the rat parotid gland as well as the morphological and histochemical changes of their granules. Light microscopy showed that cells positively stained with periodic-acid Schiff and alcian blue were sparsely distributed in the terminal clusters and acini on day 1 but had multiplied to a maximal level by day 5. They decreased in number on day 8 and were not recognizable at all by day 10. Electron microscopy revealed that the mucous cells initially contained granules of homogeneous low electron density, and then bipartite and tripartite granules with electron-dense cores were detected. By day 8 granules showing bipartite and tripartite structures and granules of homogeneous high electron density were seen to coexist in single cells. These observations suggest that mucous cells exist in parotid glands for a limited period of time and that, as the gland develops, the mucous granules come to resemble serous granules. Lectin histochemistry indicated that the secretory granules in the mucous cells were positive for peanut agglutinin, soybean agglutinin and wheat germ agglutinin, suggesting the occurrence of beta -D-galactose, alpha -D-N-acetyl galactosamine and beta -D-N-acetyl glucosamine which are the same sugar residues as those found in the granules of mature parotid serous cells. Immunostaining showed that even the low electron-dense granules in the mucous cells were weakly reactive for anti-rat parotid gland amylase; this reactivity gradually increased with development. These results suggest that mucous cell secretory granules which contain abundant glycoconjugate for a limited period during the development of the gland may change into serous granules.

Hormonal regulation of protein synthesis in the nymphal and adult male accessory reproductive gland of Locusta migratoria

Summary We have carried out in vivo and in vitro experiments to determine the effect of 20-hydroxyecdysone (20HE) on the development of the male accessory reproductive glands (MARG) of fifth instar Locusta migratoria. 20HE stimulates protein synthesis in the MARG, but only after day 2 of the final stadium. The in vitro effects of20HE and juvenile hormone III on the polypeptide profile of MARG from adults 1–10 days post-mergence were investigated using fluorographic and radiometric analyses. Synthesis of several polypeptides was influenced by both hormones in the short hyaline tubules and white tubules while in the long hyaline tubules the hormones were without effect.

Differentially regulated epithelial expression of an Eph family tyrosine kinase (fHek2) during tracheal surface airway and submucosal gland development.

A ferret model was used to evaluate the potential role of an Eph family tyrosine kinase (fHek2) in tracheal development of surface airway epithelium and submucosal glands. A partial 2.6-kb cDNA fragment of fHek2 was isolated from a ferret tracheal/lung cDNA library. Sequence analysis demonstrated that this gene is the ortholog to the previously cloned human Hek2 gene. In situ hybridization analysis of fHek2 mRNA expression on ferret tracheal developmental time points revealed an expression pattern within a subset of surface airway epithelial cells which remained relatively constant throughout tracheal development (from -2 d in utero to adult). In contrast, developing tracheal submucosal glands at 3-day postnatal time points demonstrated little fHek2 mRNA expression. However, expression of fHek2 significantly increased more than 4-fold over the course of gland development to adulthood. These findings, which demonstrate a uniquely regulated pattern of fHek2 mRNA expression between surface airway epithelium and submucosal glands, have implications on regulatory processes which control differentiation and/or maturation of secretory structures in the lung. Such findings may be useful in further delineating the mechanisms which control cellular differentiation in the lung and how these processes are abnormally regulated in hypersecretory diseases such as chronic bronchitis, asthma, and cystic fibrosis.

Roles of neurotransmitters in regulating reproductive hormone release and gonadal maturation in decapod crustaceans

Summary Experiments done in this laboratory showed 5-hydroxytryptamine (5-HT) stimulates gonadal maturation in male and female sand fiddler crabs, Uca pugilator, and red swamp crayfish, Procambarus clarkii. This action of 5-HT is indirect, 5-HT apparently stimulating release of the gonad-stimulating hormone (GSH) that is present in the brain and thoracic ganglia. For example, studies with ovarian explants showed 5-HT has no direct effect on the ovary. But, when ovarian explants were incubated with 5-HT and brain or thoracic ganglia, the incubation medium produced greater ovarian maturation than did the medium when ovarian explants were incubated with brain or thoracic ganglia alone, 5-HT presumably enhancing GSH release. In males 5-HT not only induces testicular maturation but also development of the androgenic glands. 5-HT in males, as in females, apparently triggers GSH release; but in males GSH in turn stimulates the androgenic glands which release the androgenic gland hormone, resulting in testicular maturation. In contrast, dopamine (DA) inhibits gonadal maturation in both sexes. Methionine enkephalin, like DA, slows ovarian maturation. Red pigment-concentrating hormone (RPCH), like 5-HT, stimulates ovarian maturation both in vivo and in vitro, apparently by stimulating GSH release. RPCH does not affect the ovary directly. Calcium appears to act here as a second messenger for RPCH. The implications of these findings for enhancing the culture of crustaceans is discussed.

Elucidation of a role for stromal steroid hormone receptors in mammary gland growth and development using tissue recombinants.

The use of tissue recombinants in conjunction with steroid receptor deficient mice is described as a tool to dissect the complex paracrine pathways of sex-hormone-regulated epithelial growth and ductal morphogenesis in the mammary gland and other hormone target organs. The basic methodology involves the construction of the four possible tissue recombinants composed of epithelium (E) and stroma (S) from wild-type (wt) and knock-out (KO) mice: wt-S + wt-S, wt-S + KO-E, KO-S + KO-E, and KO-S + wt-E. All tissue recombinants are grown as subrenal capsule grafts in nude mice. Following appropriate hormonal challenge epithelial growth can be studied in the four types of tissue recombinants. Such studies using estrogen receptor, androgen receptor and progesterone receptor knockout mice demonstrate that epithelial steroid receptors are neither necessary nor sufficient for hormonal regulation of epithelial proliferation. Instead, hormonal regulation of epithelial proliferation is a paracrine event mediated by hormone-receptor-positive stromal cells.

Transgenic approaches to salivary gland research.

This review discusses the use of transgenic technology for the study of salivary gland function and development. Methods for gene transfer in the salivary gland of experimental mammals are described, including use of conventional and embryonic stem cell-derived transgenic mice and direct gene transfer techniques employing recombinant adenovirus vectors. Tissue-specific expression studies in transgenic mice have defined a number of salivary gland-specific promoter/enhancers that can be used to direct transcription into different salivary cell types. The consequences of expression of various oncogenes in the salivary glands of transgenic mice for the induction of neoplasia and hyperplasia are described. Recently, the use of adenoviral vectors has been demonstrated to be a powerful new approach to transfer genes into the salivary gland. This technology should have a major impact on the study of salivary gland gene expression, as well as provide a means to express therapeutic proteins in the salivary gland.