[Morphological features of the esophagogastric transition zone at fetuses and newborns]

Morphological research of the esophagogastric transition mucosa at 35 fetuses and newborns was done. The esophagogastric transition was lined by high columnar epithelium and mucos glands. At fetuses of 22-24 week gestational age studied zone didn't have any glands. Histochemical features of the epithelium, particularly MUC5AC positive staining, corresponded to cardial type of the Barrett esophagus, defined at adults. We have revealed that mucosa of the esophagogastric transition has gastric origin and arises before birth. We found out the islets of columnar epithelium on the surface of the laminated pavement epithelium, indicated about its uneven development up to the birth. The sites of immature epithelium could be considered as transformation zones both of laminated pavement epithelium or columnar one.

Morphology and physiological changes of genital skin and mucosa

The morphology and physiology of both the vulva and vagina undergo characteristic age-related changes over a lifetime. At birth, these tissues exhibit the effects of residual maternal estrogens. During puberty, the vulva and vagina mature under the influence of adrenal and gonadal steroid hormones. During the reproductive years, the vagina responds to ovarian steroid hormone cycling, and both tissues adapt to the needs of pregnancy and delivery. Following menopause, the vulva and vagina atrophy. A rise in the prevalence of incontinence among older women increases the risk of vulvar and perineal dermatitis. This chapter covers the morphology and physiology of the genital area from infancy to old age.

[Development and formation of the mucosal immune system of the small intestine]

Morphologic and morphometric characteristics of the grouped lymphoid nodules (Peyer's patches) and of the small intestine lamina propria were studied in rats at the 19 prenatal and 1, 7, 14, 21, 90 postnatal days. The development of these structures was found to be heterochronic and fragmentary. The development of the individual components of the mucosal immune system was interrelated. The integration of the afferent and efferent limbs of the mucosal immune system with the processes of digestion and absorption, is regarded as its adaptation to the peculiarities of postnatal development of mammals and as the property of the functional system, maintaining the homeostasis of the internal milieu of the organism.

Identification of novel ciliogenesis factors using a new in vivo model for mucociliary epithelial development

Mucociliary epithelia are essential for homeostasis of many organs and consist of mucus-secreting goblet cells and ciliated cells. Here, we present the ciliated epidermis of Xenopus embryos as a facile model system for in vivo molecular studies of mucociliary epithelial development. Using an in situ hybridization-based approach, we identified numerous genes expressed differentially in mucus-secreting cells or in ciliated cells. Focusing on genes expressed in ciliated cells, we have identified new candidate ciliogenesis factors, including several not present in the current ciliome. We find that TTC25-GFP is localized to the base of cilia and to ciliary axonemes, and disruption of TTC25 function disrupts ciliogenesis. Mig12-GFP localizes very strongly to the base of cilia and confocal imaging of this construct allows for simple visualization of the planar polarity of basal bodies that underlies polarized ciliary beating. Knockdown of Mig12 disrupts ciliogenesis. Finally, we show that ciliogenesis factors identified in the Xenopus epidermis are required in the midline to facilitate neural tube closure. These results provide further evidence of a requirement for cilia in neural tube morphogenesis and suggest that genes identified in the Xenopus epidermis play broad roles in ciliogenesis. The suites of genes identified here will provide a foundation for future studies, and may also contribute to our understanding of pathological changes in mucociliary epithelia that accompany diseases such as asthma.

Ultrastructural dynamics of the human endometrium from 14 to 22 weeks of gestation

In order to elucidate the ultrastructural dynamics of endometrium differentiation, uterine samples of fetuses aged 14 to 22 weeks of gestation (WG) were analyzed. Samples were processed for light (LM), transmission (TEM) and field-emission scanning electron microscopy (FE-SEM). Initial stratification of the uterine wall occurred at 14 WG: endometrial, myometrial, and perimetrial primordia were identified. At this age, the endometrial epithelium was simple columnar to pseudostratified and consisted of microvillous cells. Blood capillaries developed mainly in the stroma and between the myometrium and perimetrium primordia. At 18-20 WG the endometrial epithelium became clearly pseudostratified, with active ciliogenesis and a predominance of microvillous cells. Primordia of tubular glands were present at 20 WG. Microvillous cells still predominated in the endometrial epithelium at 21-22 WG and showed morphological features of apoptosis. The endometrial stroma at this stage was organizing into a thick lamina propria provided with subepithelial capillary plexuses. However, the stroma was formed by still undifferentiated mesenchymal cells during the whole period of study. Our data showed that the epithelial differentiation and distribution in the uterus occur in the human fetus in a similar way as in the adult. The above events are likely the expression of an early developmental patterning and related to future reproductive processes, such as the regulation of gamete passage and blastocyst implantation. Because the structure of the adult uterus is determined by the degree of paramesonephric duct fusion, septum absorption, and differentiation of the uterine primordial layers, our study may contribute toward clarifying to normal urogenital development.

Expression of mucosal chemokines TECK/CCL25 and MEC/CCL28 during fetal development of the ovine mucosal immune system

CCL25/TECK and CCL28/MEC are CC chemokines primarily expressed in thymic dendritic cells and mucosal epithelial cells. The cognate receptors of CCL25 and CCL28, CCR9 and CCR10, respectively, are mainly expressed on T and B lymphocytes. In human, mouse and pig, CCL25 and CCL28 play a key role in the segregation and the compartmentalization of the mucosal immune system through recruitment of immune cells to specific locations. However, little is known about their role in the ontogeny of the mucosal immune system during fetal development. In the present paper, we report the cloning and the sequencing of ovine CCL25, CCL28, CCR9 and CCR10 and the subsequent assessment of their mRNA expression by q-polymerase chain reaction in several tissues, including thymus, gut-associated lymphoid tissue and mammary gland, from young and adult sheep and in the fetal lamb during the development of the immune system. CCL25 mRNA was highly expressed in thymus and gut while CCL28 mRNA was more expressed in large intestine, trachea, tonsils and mammary gland, especially at the end of gestation. These results are consistent with observations in other species suggesting similar roles for these chemokines in sheep. In fetuses, mRNA of CCL25, CCL28 and their receptors are expressed early in the thymus and mucosal tissues, including the small intestine and the nasal mucosa. Furthermore, their expression increased towards the end of gestation. Consequently, we hypothesize that CCL25 and CCL28 play an important role in the lymphocyte colonization of fetal tissues, enabling the development of a functional immune system.

The histological findings in the gastroesophageal junction of fetuses

The development of the esophageal and gastric mucosa in the gastroesophageal junction was studied in 61 fetuses of 13-41 weeks of the gestational age. During the 13th-15th week, the esophageal multilayered epithelium was covered by a continuous layer of columnar mucous ciliated cells which were present only focally till the 25th week and disappeared later. Before the 15th week, the gastric mucosa was formed by pits only. The glands started as proliferating tubules in the basal parts of the pits in the 15th week. Further, they differentiated into oxyntic glands. The mucosa of the corpus was fully developed in the 27th week. The cardiac mucosa was absent in all the 10 fetuses examined between the 27th and 41st week of gestation. This supports the view that the gastric cardiac mucosa is not a physiological structure but that it results from glandular metaplasia of the distal esophageal mucosa due to gastroesophageal reflux.

Extracellular matrix protein expression during mouse detrusor development

BACKGROUND/PURPOSE

Extracellular matrix proteins are implicated in regulating cell proliferation and differentiation. The authors systematically analysed the expression of elastin; collagen types I, III, IV; laminin; and fibronectin during mouse detrusor muscle development, a period during which downregulation of detrusor proliferation and increasing smooth muscle differentiation is known to occur.

METHODS

Embryonic days 14 (E14) and 18 (E18), and postnatal day 1 (D1) and week 6 (6wk) were examined, a period spanning the inception of the bladder to postnatal maturity. Immunohistochemistry of whole bladders was used to immunolocalise protein expression, and Western blot of dissected detrusor layers was used to semiquantify soluble protein expression.

RESULTS

All proteins were detected at all 4 stages. Statistically significant increases were documented for elastin (E14 to 6wk), collagen type I (E18 to 6wk), collagen type III (D1 to 6wk) and laminin (E14 to 6wk). Fibronectin levels were relatively high up to D1, after which levels declined significantly. Collagen type IV levels decreased significantly (E18 to 6wk).

CONCLUSIONS

The authors postulate that changing levels of laminin and fibronectin have opposing effects on the transition from proliferating primitive mesenchymal cells to differentiated detrusor muscle. Furthermore, changes in collagen type III and elastin may be important for bladder compliance.

Foxp4: a novel member of the Foxp subfamily of winged-helix genes co-expressed with Foxp1 and Foxp2 in pulmonary and gut tissues

In this study, we describe the isolation and characterization of Foxp4, a new member of the Foxp subfamily of winged-helix transcription factors. The full-length mouse Foxp4 cDNA encodes a 685-amino-acid protein that is similar to Foxp1 and Foxp2. Foxp4 gene expression is observed primarily in pulmonary, neural, and gut tissues during embryonic development. To compare the protein expression patterns of Foxp4 to Foxp1 and Foxp2, specific polyclonal antisera to each of these proteins was used in immunohistochemical analysis of mouse embryonic tissues. All three proteins are expressed in lung epithelium with Foxp1 and Foxp4 expressed in both proximal and distal airway epithelium while Foxp2 is expressed primarily in distal epithelium. Foxp1 protein expression is also observed in the mesenchyme and vascular endothelial cells of the lung. At embryonic day 12.5, Foxp1 and Foxp2 are expressed in both the mucosal and epithelial layers of the intestine. However, Foxp2 is expressed only in the outer mucosal layer of the intestine and stomach later in development. Finally, Foxp4 is expressed exclusively in the epithelial cells of the developing intestine, where, in late development, it is expressed in a gradient along the longitudinal axis of the villi.

Microvascularization of the mucocutaneous junction of the eyelid in fetuses and neonates

The aim of this study was to specify the microvascularization of the junctional region between the integuments of the superficial surface of the free margin of the eyelid and the palpebral conjunctival mucosa. The study was carried out using histological or transparified slices of upper and lower eyelids taken from fetuses and neonates, in which the vascular system was injected with agarized China ink. The mucocutaneous junction of the eyelid is located at the posterior border of the free margin and extends to its deep surface. It has vascular similarities to the oral cavity and the nasal pyramid. Under a thickened avascular epithelium, there is a papillary network composed of characteristic loops that are less raised than in the lips but more developed than in the nose. The superficial and deep vascular reticular networks are comparable in fundamental arrangement to those of other junctional zones. Thus, the palpebral mucocutaneous junction shows cutaneous-type microvascularization, just like the other junctional zones of the head.

Ex vivo development of functional human lymph node and bronchus-associated lymphoid tissue

We introduce a novel in vivo model of human mucosal immunity, based on the implantation of human fetal bronchial mucosa and autologous peribronchial lymph node (PLN) in the severe combined immunodeficiency (SCID) mouse. In the SCID host, human fetal bronchi implanted alone retain macrophages and mast cells but lose T cells. In contrast, fetal bronchi co-implanted with PLN contain, in addition to macrophages and mast cells, numerous T cells and B cells, often clustered in intramucosal bronchus-associated lymphoid tissue (BALT). Functionally, bronchus-PLN cografts are able to mount robust alphabeta and gammadelta T-cell-mediated immune responses to Pseudomonas aeruginosa and 3,4-epoxy-3-methyl-1-butyl-diphosphate challenges. No other autologous lymphoid organ (bone marrow, thymus, liver) allows for BALT development in co-implanted bronchi, which suggests special ontogenetic and functional relations between extramucosal PLN and intramucosal BALT. Overall, the bronchus-PLN cograft appears as a promising model for human bronchial immune development and function. Our study is the first to document long-term ex vivo maintenance of functional human lymph nodes as native appendices to mucosal tissue. Our results, therefore, suggest a simple strategy for developing similar experimental models of human immune function in other mucosae.

Degeneration and regeneration of the lip mucosal epithelium after cryo treatment in mice

The process of degeneration and regeneration of the lip mucosal epithelium after cryo treatment was observed by transmission electron microscopy. The epithelial cells were degenerated by the formation of ice crystals and subsequently detached from the basement membrane, forming a blister cavity. The separation occurred between the epithelial cells and the lamina densa, leaving a small amount of cell debris on the lamina densa. The surviving cells at the periphery of the blister cavity, especially the cells in the basal half of the epithelium, provided the regeneration cells. They migrated over the cell debris, attached to the lamina densa and gradually phagocytozed it. Finally, they formed hemidesmosomes with the old lamina densa. The connections between the epithelial cells by desmosomes were so tight that desmosomes were preserved even between dead cells and between dead and living cells. Regenerating cells were moving in a multilayered form, remaining connected to each other by the dosmosomes. They were seen to divide by mitosis and thereby increase the number of the cell layer, whilst maintaining their connections with the neighbouring cells.

Ontogeny of pulmonary neuroendocrine cells which express the alpha-subunit of guanine nucleotide-binding protein Go

In order to ascertain that alpha-subunit of guanine nucleotide-binding protein Go (Go alpha)-positive cells in the lung epithelia are pulmonary neuroendocrine cells (PNECs), we carried out an immunohistochemical study in young adult and fetal lungs of rodents and in cultured fetal lung explants. Serial sections showed that Go alpha-positive cells were immunostained for calcitonin gene-related peptide and serotonin in young adult mouse, rat, and hamster lungs and that these cells are, therefore, PNECs. In the fetal lungs of hamster and mouse, Go alpha-positive PNECs appeared in the epithelium of the lobar bronchus by gestational day 13 in hamster and by day 15.5 in mouse, and they increased with a proximal-to-distal wave during the late fetal period. Explants of immature lung from the fetal hamster on gestational day 11 were cultured. After 2 days of culture, Go alpha-positive PNEC clusters appeared in the main and lobar bronchi and many PNEC clusters were seen after 4 days of culture. To determine the functional significance of Go in the development of the fetal lung, pertussis toxin, a Go inhibitor, was added to the medium, and changes in branching morphogenesis and PNEC development were studied. Although branching morphogenesis was not disturbed by pertussis toxin, the toxin treatment induced large PNEC clusters in the cultured lung explant. In summary, we showed that Go alpha is a neuroendocrine marker for PNECs and that Go alpha-positive cells appear along with development of PNECs in fetal hamster lung in vivo and in vitro. The functional significance of Go in the development of fetal lung is obscure, but signals mediated through this GTP-binding protein could be related to some functions of PNECs.

Lineage commitment and maturation of epithelial cells in the gut

The dynamic concepts of gut epithelial cell populations which heralded the era of modern gut cell biology have been generally substantiated by recent studies and are still being correlated with functional properties. Multipotent stem cells are anchored in specific locations along the gut epithelium where decisions concerning proliferation and differentiation/migration pathways are made. Stem cells give rise to lineage precursors which transform into transit cells and sequentially express lineage specific features during their differentiation program. Morphologically and functionally mature cells along the gut epithelium are dynamically heterogeneous. 1) The squamous lineage of the esophagus forms a stratified epithelium which has an average turnover time of about 7. 5 days. 2) In the stomach, the oxyntic pit-gland unit includes pit, zymogenic and parietal cells which respectively migrate outwards, inwards, and in both directions; their turnover times average 3, 194 and 54 days, respectively. 3) The mucous units of the pyloric antrum are populated by pit cells which migrate outwards and gland cells which migrate inwards; their turnover times are about 3 and 1-60 days, respectively. 4) In the crypt-villus units of the small intestine, while both absorptive and goblet cells migrate outwards and for each the turnover time is about 3 days, Paneth cells migrate inwards and their turnover time is about 15 days. 5) In the crypts of the descending colon, both vacuolated-columnar and goblet cells migrate outwards and for each the turnover time is about 5 days. The ascending colon has an additional cell type called deep crypt secretory cells which migrate inwards and their turnover time is about 14-21 days. Finally, while the factors maintaining the gut epithelium in a steady state remain to be elucidated, this epithelium represents a remarkable system for studying the biological features of stem cells and their hierarchies.

Lineage commitment and maturation of epithelial cells in the gut

The dynamic concepts of gut epithelial cell populations which heralded the era of modern gut cell biology have been generally substantiated by recent studies and are still being correlated with functional properties. Multipotent stem cells are anchored in specific locations along the gut epithelium where decisions concerning proliferation and differentiation/migration pathways are made. Stem cells give rise to lineage precursors which transform into transit cells and sequentially express lineage specific features during their differentiation program. Morphologically and functionally mature cells along the gut epithelium are dynamically heterogeneous. 1) The squamous lineage of the esophagus forms a stratified epithelium which has an average turnover time of about 7. 5 days. 2) In the stomach, the oxyntic pit-gland unit includes pit, zymogenic and parietal cells which respectively migrate outwards, inwards, and in both directions; their turnover times average 3, 194 and 54 days, respectively. 3) The mucous units of the pyloric antrum are populated by pit cells which migrate outwards and gland cells which migrate inwards; their turnover times are about 3 and 1-60 days, respectively. 4) In the crypt-villus units of the small intestine, while both absorptive and goblet cells migrate outwards and for each the turnover time is about 3 days, Paneth cells migrate inwards and their turnover time is about 15 days. 5) In the crypts of the descending colon, both vacuolated-columnar and goblet cells migrate outwards and for each the turnover time is about 5 days. The ascending colon has an additional cell type called deep crypt secretory cells which migrate inwards and their turnover time is about 14-21 days. Finally, while the factors maintaining the gut epithelium in a steady state remain to be elucidated, this epithelium represents a remarkable system for studying the biological features of stem cells and their hierarchies.

Development of the human gastrointestinal tract: twenty years of progress

A combination of approaches has begun to elucidate the mechanisms of gastrointestinal development. This review describes progress over the last 20 years in understanding human gastrointestinal development, including data from both human and experimental animal studies that address molecular mechanisms. Rapid progress is being made in the identification of genes regulating gastrointestinal development. Genes directing initial formation of the endoderm as well as organ-specific patterning are beginning to be identified. Signaling pathways regulating the overall right-left asymmetry of the gastrointestinal tract and epithelial-mesenchymal interactions are being clarified. In searching for extrinsic developmental regulators, numerous candidate trophic factors have been proposed, but compelling evidence remains elusive. A critical gene that initiates pancreas development has been identified, as well as a number of genes regulating liver, stomach, and intestinal development. Mutations in genes affecting neural crest cell migration have been shown to give rise to Hirschsprung's disease. Considerable progress has been achieved in understanding specific phenomena, such as the transcription factors regulating expression of sucrase-isomaltase and fatty acid-binding protein. The challenge for the future is to integrate these data into a more complete understanding of the physiology of gastrointestinal development.

[Endocrine apparatus of the epithelium of the appendicular mucosa (the appendix-- an endocrine gland, functioning in the embryonal period?]

Based on the concept on gastroenteropancreatic system, endocrinocytes of which are diffusely scattered throughout the digestive tract epithelium and are found in pancreatic islets, an analysis of endocrine apparatus of epithelium in human appendicular mucosa was performed at different stages of ontogenesis. The response of appendicular endocrinocytes to clinical pathology of both this organ and the entire organism was studied. On the base of the analysis of the appendix function from morphological view, the authors proposed a hypothesis postulating it to be an organ equal to an actively functioning endocrine gland and its unique role on early stages of embryogenesis.

Fetal airway wound repair: a new frontier

PURPOSE

Fetal dermal repair is regenerative and scarless until middle to late gestation, when there is a transition to fibrotic repair. Fetal skeletal muscle and tendon undergo repair with fibrosis similar to the process in adults. This study addresses whether fetal mucosal healing is regenerative and scarless.

METHODS

Anesthetized pregnant rabbits underwent laparotomy and controlled hysterotomy at 21 to 23 days' gestation (term is 31 days). A midline thyrotomy was made, followed by cricoidotomy and circumferential cauterization of the subglottic mucosa. A similar insult was applied to weanlings. The data were collected in 2 groups. One group was followed to term and killed at 4 weeks. A second group was killed after 6 days (30 days' gestation). The weanlings were killed at similar points. The larynges were harvested and processed for histological and morphometric analysis.

RESULTS

Three litters were followed to term. Of these, 1 was not recovered; in the other two, 7 of 8 manipulated fetuses were found and 3 of 8 were viable. The fourth litter was harvested after 6 days; all 4 injured fetuses were recovered and viable. All animals in the fetal injury groups healed with complete regeneration of the airway mucosa. In contrast, weanlings injured post partum had mucosal inflammation, necrosis, and ulceration; squamous metaplasia and basal cell hyperplasia were also found. There were fibrosis, granulation tissue, and inflammation in the lamina propria; chondritis, cartilaginous necrosis, chondrolysis, and perichondritis were also found.

CONCLUSIONS

Fetal airway mucosal healing is regenerative and, thus, scarless. This study provides further support for the thesis that skin and mucosa respond to injury similarly in both the developmental and postpartum stages, and that subglottic stenosis is reasonably thought of as the "hyperplastic scar" of the airway. These results have potential therapeutic applications for mucosal wound management.

Selective disruption of lymphotoxin ligands reveals a novel set of mucosal lymph nodes and unique effects on lymph node cellular organization

Lymphotoxin (LT) provides a critical signal for the genesis of lymph nodes (LN) in mice. Here we show that mice treated in utero with LT beta-R-Ig, which binds to the membrane LT alpha 1 beta 2 heterotrimer, lacked most LN, yet retained a set of mucosal surface draining LN. Since mice genetically deficient in LT alpha lack all LN, including the mucosal set, we hypothesize that a novel LT alpha-dependent pathway controls their genesis. This novel set of mucosal LN cannot be discriminated on the basis of addressin expression. The discovery of LN in mice treated with LT beta-R-Ig fusion protein in utero allowed us to compare the roles of membrane LT alpha beta or soluble LT alpha/tumor necrosis factor (TNF) in the development of cellular organization in LN and spleen. Our results indicate that both membrane LT alpha beta and soluble LT alpha/TNF mediate T-B cell segregation and the organization of B cell follicles in spleen and LN. Interestingly, while antagonism of membrane LT alpha beta or soluble LT alpha/TNF prevented germinal center (GC) formation in spleen, antagonism of soluble LT alpha/TNF had no effect on LN formation. The data suggest that multiple LT/TNF ligands control B cell follicle organization in the spleen and LN of adult mice, and that the requirements for LT/TNF ligands in GC formation are distinct in the different lymphoid organs.

Structure and function of the adventitial and mucosal nerve plexuses of the bronchial tree in the developing lung

1. The aim of the present study was first to determine when airway smooth muscle first appears in the airways of the developing foetal lung and when its contractility is mature and, second, when the airway smooth muscle becomes innervated, both structurally and functionally. 2. Narrowing and relaxation of the airways of the intact bronchial tree from the lungs of foetal pigs at varying stages of gestation was recorded by real time video microscopy. Nerves and smooth muscle were stained immunohistochemically and their spatial relationships were visualized by confocal microscopy. 3. From early in gestation (pseudoglandular stage/branching morphogenesis), airways were covered with a single layer of smooth muscle cells orientated cylindrically around the airway wall. Thick nerve trunks containing loosely packed nerves, with ganglia forming at their junctions ensheathed the airways to the growing tips, with a network of fine varicosed nerves lying on the smooth muscle cells. Some of these nerves were functional and cholinergic, as electrical field stimulation caused substantial narrowing that was blocked by atropine and by tetrodotoxin. By mid-term, an extensive plexus of nerves, well-defined ganglia and varicosed nerves to the smooth muscle had developed. Some nerves extended through the airway smooth muscle to form the elements of a mucosal nerve plexus in conjunction with developing vascular tissue forming a bronchial circulation. In 3 week postnatal pigs the distal and terminal airways were densely supplied with varicosed nerves to the smooth muscle. The ganglia were more centrally located. 4. An abundant network of calcitonin gene-related peptide (CGRP) nerves with prominent nerve endings lay just below the surface of the epithelium. The nerve bundles to the terminal arterioles in the mucosa also contained CGRP-positive fibres as well as sympathetic nerves (neuropeptide Y- and tyrosine hydroxylase-positive). It is hypothesized that these epithelial and arteriolar CGRP nerves form the local axon reflex purported to cause neurogenic inflammation. 5. The spontaneously active tone exerted by the airway smooth muscle from early in gestation is hypothesized to provide the force across the airway wall and adjacent parenchyma that is the stimulus for lung growth in foetal life.

[The ultrastructure of the Eustachian tube]

To observe the ultrastructure of mucous membrane of Eustachian tube in human being, ninteen human's Eustachian tube from various ages, were divided into tympanic segment, isthmus and pharyngeal segment and observed under SEM. The results showed that the epithelium of Eustachian tube consisted of ciliated cells, nonciliated cells and goblet cells. At the isthmus, the bone and cartilage junction, the cells got crowded, and there were more and more goblet cells from tympanic side to pharyngeal side, as well as the cilia of ciliated cell leaned towards the pharyngeal side. The upper one third part of Eustachian tube was covered mostly by nonciliated cells, the floor and lower parts were ciliated cells. It was concluded that the upper parts of Eustachian tube's wall played an important role in maintaining equation of pressure in middle ear, and the floor and lower parts in providing an active mucociliary mechnism. The defence system of the Eustachian tube mucous membrane had developed during the fetal stage and was well established at birth.

Histochemical study of lectin binding in the human fetal minor salivary glands

The emerging synthesis of glycoconjugates containing specific oligosaccharides in developing human fetal labial and lingual salivary glands has been investigated by lectin histochemistry. An avidin-biotin technique was used to study the binding of lectins from Ulex europeus I (UEA-I), Dolichos biflorus (DBA), Glycine maximus (SBA), Helix pomatia (HPA), Arachis hypogaea (PNA) and Triticum vulgare (WGA) to specific sugars on sections of tissue from labial glands, glands of Blandin and Nuhn, glands of von Ebner and the dorsoposterior lingual salivary glands. Incipient synthesis of glycoconjugates in early glands and their presence in the cells and ducts of the later glands was shown. The study also showed a time-related increase in both staining intensity and binding sites of serous acinar cells from all glands and for all lectins used. For mucous cells, peak intensity of staining was reached by the middle phase of development. During later gland development this intensity was maintained in dorsoposterior lingual glands but tended to decline in labial glands. The various lectins showed different degrees of binding but UEA-I lectin generally bound the L-fucose sugar group in all salivary glands at all gestational ages. The results showed that lectins appear to bind to the oligosaccharides on epithelial cell surfaces of fetal salivary glands at all stages of development. The degree of change depends upon the stage of differentiation and maturation of the glands.

Extrahepatic bioactivation of aflatoxin B1 in fetal, infant and adult rats

Whole-body autoradiography of 3H-labelled aflatoxin B1 (3H-AFB1) in female non-pregnant adult and infant Sprague-Dawley rats showed retention of tissue-bound radioactivity, in addition to the liver, in the mucosa and some glands in the nose, and in the mucosa of the nasopharynx, trachea, bronchioles, colon and caecum. The extrahepatic binding was most pronounced in the infant rats. In a rat pretreated with the glutathione (GSH)-depleting agent phorone, bound labelling was also seen in the superficial part of the mucosa of the glandular stomach. Autoradiography of 3H-AFB1 in pregnant rats showed a marked localization of bound AFB1-metabolites in the fetal nasal olfactory and tracheal mucosa. In vitro experiments demonstrated that the nasal olfactory mucosa had a much higher capacity than the liver to form AFB1-metabolites which bound to DNA and protein. The bioactivation was observed both pre- and post-natally and increased with age. Bioactivation was found also in the caecum, the colon and the lateral nasal gland (Steno's gland), but not in the small intestine, oesophagus or Harderian gland. Our results indicated that glutathione-S transferase activity catalysing the AFB1-8,9-epoxide GSH-conjugation was present in the nasal olfactory mucosa and liver at all pre- and post-natal ages examined. Several of the extrahepatic tissues able to bioactivate AFB1 have been reported to be targets for the carcinogenicity of the substance. Our results indicate that the extrahepatic carcinogenicity of AFB1 is correlated to a local bioactivation in the sensitive tissues.

The vascular architecture of human fetal oviduct: a scanning electron microscopic study of corrosion casts

Vascular architecture was investigated, in 18-21 week old human fetuses, for the first time with the use of corrosion casting and scanning electron microscopy, which offer high resolution and three-dimensional images of the vascular networks. The general arrangement of large vessels was similar to that described for the mature oviduct; however, the intramural vasculature of the muscular layer and mucosal folds consisted predominantly of capillary and sinusoidal networks. A characteristic feature of the fetal oviduct was a prominent sub-serosal venous plexus, which was most extensive in the isthmic segment. The relatively low degree of differentiation found in the fetal oviduct vasculature seems to reflect its functional immaturity.

Immunohistochemical localization of cystic fibrosis transmembrane conductance regulator in human fetal airway and digestive mucosa

The cellular distribution of the cystic fibrosis transmembrane conductance regulator (CFTR) in human fetal digestive and respiratory mucosa has been studied by immunohistochemistry. The streptavidin-biotin immunoperoxidase method was applied to paraffin-embedded specimens collected from normal fetuses ranging from 7 to 39 wk of gestation. By the 7th wk, CFTR protein was strongly detected in the yolk sack; in contrast, the staining was weak in the undifferentiated epithelium of the intestine and the airways. At 12 wk, the intestine showed strongly and diffusely stained enterocytes and a basal cytoplasmic reactivity in the first secretory cells. During development, only slight changes could be detected in the digestive epithelial distribution of CFTR. In the airways, the CFTR distribution followed the cephalocaudal maturation. In the tracheal ciliated cells, the CFTR protein was diffusely detected in the cytoplasm as early as 7 wk. After 24-25 wk, CFTR was localized at the apical domain of the ciliated cells and was also present in the collecting ducts and in the glands of the airways, predominantly in the periphery of the acini. Our data suggest that the CFTR is present as early as 7 wk during organogenesis and probably plays an important role during fetal life. There is an evolution in the CFTR distribution during airway development, whereas, in the intestine, CFTR is highly expressed through the epithelium as early as 12 wk and keeps the same distribution until birth.

[Morphogenesis and modifications of the respiratory epithelium]

The tracheobronchial tree begins to form during the fourth week of development through a series of dichotomic divisions of an entoblastic evagination. The morphogenesis and maturation of the respiratory tract depend both on the nature of the extracellular matrix which facilitates cell migration and on epithelial-mesenchymal interactions which induce the proliferation and differentiation of epithelial cells. The study of the plasticity and the phenotypic modifications of secretory cells during both development and inflammatory remodeling of the tracheobronchial mucosa suggests an important role for secretory cells during ciliogenesis and repair.

Effects of hormones on functional differentiation of mouse respiratory epithelium

The effects of corticosteroids and thyroxine on morphogenesis and differentiation of fetal respiratory epithelium were tested in serum-free culture. Strips from the margins of 16-day fetal mouse lungs, containing future respiratory branches, were cultured in medium containing growth factors plus different concentrations of dexamethasone and/or thyroxine. After 5 days, some of the cultures were processed for electron microscopy and the rest were used to quantitate unsaturated and saturated phosphatidylcholine. In the absence of thyroxine and dexamethasone, the lung tissue developed the equivalent of one more day in utero during the 5 days of culture, perhaps because of residual hormone in the tissue. Thyroxine and dexamethasone in concentrations compatible with normal physiological conditions permitted normal development from the pseudoglandular stage to the saccular stage, differentiation of respiratory cell types, and normal surfactant accumulation. Thyroxine alone gave essentially the same lack of morphological maturation and accumulation of disaturated phosphatidylcholine as culture in the absence of all hormone, but columnar epithelial cells held increased numbers of lamellar bodies. Dexamethasone alone at 10(-6) M gave essentially normal development. Dexamethasone at 10(-9) M was sufficient to permit almost normal development when combined with 10(-7) M thyroxine. We conclude that dexamethasone is required for normal maturation of the fetal lung and that thyroxine acts synergistically to lower the dexamethasone requirement. The presence of apparently authentic lamellar bodies under some conditions of low disaturated phosphatidylcholine accumulation make this morphological criterion suspect as a test for differentiation of type II cells.

Cell proliferation in chick oral membrane lags behind that of adjacent epithelia at the time of rupture

Radioautographic analysis showed that ectoderm and endoderm cells in chick oral membrane continued to label with tritiated thymidine through the period of rupture, but their frequency of labeling was significantly lower than those of adjacent epithelia. Frequency of labeling increased in adjacent ectoderm and endoderm, while oral membrane rates remained relatively low, suggesting that growth in the membrane lags relative to adjacent epithelia. Relatively greater proliferation in adjacent epithelia could generate tension and pull apart the thinned oral membrane. Differentials in rates of cell proliferation, when considered along with knowledge of cellular rearrangements following changes in basal lamina and matrical components, suggest that differential growth is an important force in rupture of the avian oral membrane.

Electron microscopic study on the esophageal mucosa in human fetuses

Morphogenetic studies of the esophageal mucosa in human fetuses have been few and there is only one report at the ultrastructural level. We thus studied the esophageal mucosa in human fetuses (at the gestational ages from the 7th to 21st week) by scanning (SEM) as well as transmission electron microscopy (TEM). Our results and the review of the literature lead to the following conclusions: 1) Primary cilia were seen in the 7th and 8th week of gestation. 2) Ciliated cells appeared around the 8th week of gestation. They increased in number according to the fetal ages, but gradually decreased after the 14th week of gestation. Their degenerative process at the ultrastructural level was similar to that reported previously. 3) The stratified squamous epithelia appeared at the 14th week of gestation, but the squamous cells remained immature even at the 21st week. 4) Glycogen granules in non-ciliated cells decreased as the differentiation of the cells proceeded, suggesting that they provide an energy source necessary for the cell differentiation.

The distribution of mucosal lymphoid nodules in the equine respiratory tract

Mucosal lymphoid nodules were identified within the equine respiratory tract by an acetic acid fixation technique. Nodules were identified in foetuses from nine months gestational age, and estimates of total and regional nodule populations were made in foetal, neonatal and adult horses. Nodules occurred at specific sites within the tract, which probably relate to areas where inhaled antigens accumulate. The largest populations of nodules occurred in the nasopharynx and larynx, with smaller numbers in the nasal cavity, trachea and bronchi. There was an age-related change in the size of these nodule populations, with an increase in number from late gestation to the neonatal period to early adulthood (up to 5 years of age), followed by a decrease in older adults.

Electron microscopic study on the epiglottic mucosa in human fetuses

The differentiation of the epiglottic mucosa in human fetuses has so far been studied only by light microscopy. So, we studied the epiglottic mucosa in human fetuses (at gestational ages from the 7th to 21st week) by scanning (SEM) and transmission electron microscopies (TEM), and could disclose more detailed features of cellular differentiation of this mucosa. These results and the review of the literatures lead to the following conclusions: 1. Primary cilia appeared in the epiglottic mucosa around the 7th week of gestation. 2. Ciliated cells and the stratified squamous epithelium of the lingual surface appeared at the similar period as reported by others, but our study revealed that the squamous cells are immature even at the 21st week. 3. Glycogen granules in non-ciliated cells decreased paralleling the differentiation of the cells, suggesting that they provide a source of energy necessary for the cell differentiation.

Tracheal submucosal gland development in the rhesus monkey, Macaca mulatta: ultrastructure and histochemistry

The submucosal glands are thought to be the primary source of the mucus overlying the primate trachea and conducting airways. This study characterizes the development of submucosal glands in the trachea of the rhesus monkey. Tracheas from 46 age-dated fetal, 8 postnatal and 3 adult rhesus were fixed in glutaraldehyde/paraformaldehyde and slices processed for electron microscopy. The earliest (70 days gestational age (DGA)) indication of gland development was the projection of a group of closely packed electron lucent cells with few organelles and small pockets of glycogen into the submucosa. This configuration was observed up to 110 DGA. In fetuses younger than 87 DGA it was present almost exclusively over cartilaginous areas. Between 80 and 140 DGA, a cylinder of electron lucent cells projected into the submucosal connective tissue perpendicular to the surface. In fetuses younger than 100 DGA, it was restricted to cartilaginous areas. By 90 DGA, some glycogen containing cells in proximal regions contained apical cored granules. By 106 DGA, cells in proximal areas contained apical electron lucent granules. More distal cells had abundant GER and electron dense granules. The most distal cells resembled the undifferentiated cells at younger ages. Ciliated cells were present in the most proximal portions of glands at 120 DGA. This glandular organization was found in older animals, including adults, with the following changes: abundance of proximal cells with electron lucent granules increased; abundance of distal cells with electron dense granules increased; and abundance of distal cells with abundant glycogen and few organelles decreased. We conclude that submucosal gland development in the rhesus monkey: is primarily a prenatal process; occurs first over cartilage; continues into the postnatal period; and involves secretory cell maturation in a proximal to distal sequence with mucous cells differentiating before serous cells.

Mucociliary activities in fetal rabbits

There have been many morphological investigations on the generation of respiratory epithelium. However, the mucociliary activity of fetal respiratory epithelium has never yet been discussed. In the present work, ciliary activity and mucociliary function in the nose and the trachea of fetal rabbits were studied and, moreover, their respiratory epithelial cells were observed by scanning and transmission electron microscopy. Ciliary activity as noted on the 26th day of fetal life (day 26) for the first time in both of the nasal and the tracheal region and this activity was already equivalent to that in adult rabbits. Mucociliary transport function in either region was first noted on day 27. A quantitative as well as a qualitative immaturity of the respiratory epithelium was recognized on the last day of observation (day 29). The quantitative immaturity is characterized by 1) the ratio of ciliated to non-ciliated cells being lower than in the adult epithelium, 2) each ciliated cell possessing about three-fifths as many cilia as those of a full-grown cell, and 3) some cilia being smaller than full-grown ones and the qualitative immaturity by the directional disorder of the basal foot. No differences were observed between a cilium on day 25 or earlier, another on day 26 or later, and a full-grown cilium. It is suggested that cilia of the respiratory epithelium are morphologically prepared for motion and are activated on day 26 by changes in their surroundings, and that the poorer mucociliary transport in fetuses despite an almost normal ciliary beating is due in fairly large part to their qualitative immaturity (directional disorder of the basal foot).

Mucous glands in the developing human rhinopharynx

In 42 fetuses and prematures, the entire mucosa from the rhinopharynx was stained by various whole-mount methods. The development, growth, spread, distribution, situation, and size of the glands were determined. The development starts in the 11th week below the tubal orifice, whence the glands spread to the entire rhinopharynx. The number increases gradually by about 60-70 glands a week. By the 23rd week, there are 1,100-1,200 glands in the rhinopharynx. After that juncture, there is presumably no further new formation. The density and size of the glands were at a maximum in Rosenmüller's recess, below the tubal orifice, and in the salpingopharyngeal fold, least anterior to the tubal orifice and at the junction to the pharynx. The role of the sero-mucous glands in the rhinopharynx under normal and abnormal conditions is dicussed.

Middle-ear mucosa in newborn infants

To ascertain whether the mucous glands constitute a normal or abnormal component of the mucous membrane in the osseous Eustachian tube and middle ear, 28 prematures and newborn infants were studied. The entire mucous membrane from the Eustachian tube and middle ear was removed and stained by the PAS-alcian blue whole mount method. No mucous glands were found in the osseous tube or middle ear, although the conditions for their formation were present, there being goblet cells and stratified columnar epithelium in the osseous tube and anterior part of the middle ear. Thus, the mucous glands do not form a normal component of the middle ear mucosa, although they may be demonstrated in ears which are clinically quite normal. Minor and short lasting catarrhal affections of the tubal and middle ear mucosa — Which occur in everyone during childhood or later without leaving any other sequelae in the middle ear — may lead to the formation of a few glands. As long as only a few glands are present, the production of mucus is negligible and does not entail clinical symptoms. In chronic middle ear diseases the density of glands is relatively high, and the mucus or mucus-admixed discharge occurring in these diseases is an active product of the mucous glands and goblet cells.

Production of mucus in the middle ear and Eustachian tube. Embryology, anatomy, and pathology of the mucous glands and goblet cells in the Eustachian tube and middle ear

On the basis of quantitative studies of the mucus elements in 144 temporal bones and more than 5,000 biopsies the mucus producing capacity of the mucosa in the middle ear and Eustachian tube under normal conditions as well as in acute and chronic middle ear diseases is reviewed. In completely normal middle ears there was a very low goblet cell density and no mucous glands. Production of mucus does take place, but it is very slight. In acute conditions the goblet cell density in the Eustachian tube and middle ear increases, and metaplastic changes of the mucosa may occur, with formation of subepithelial and intraepithelial mucous glands. In chronic diseases, such as secretory otitis, there is a high gland and goblet cell density, which explains the increased production of mucus. In adhesive otitis the gland density is great, it is true, but most glands have become inactive and have degenerated. In chronic suppurative otitis, cholesteatoma, and sequelae to chronic otitis the goblet cell and gland density is moderately increased, but there are very marked individual variations which explain the great difference in the production of mucus. In active chronic diseases the mucus elements may increase enormously, and the mucus producing capacity of the epithelium may reach the heights of that of the respiratory mucosa.