Tracheobronchial epithelium of the sheep: II. Ultrastructural and morphometric analysis of the epithelial secretory cell types

In a light microscopic study we have described the morphology and distribution of six distinct, granule-containing cells in the tracheobronchial epithelium of sheep lung. We designed the present study to determine qualitatively and quantitatively whether these six cell types differ in ultrastructural morphology. Cell height varied from 30.6 micron for mucous cell M1 to 9.6 micron for Clara cells. Cell width varied from 21.2 micron for M1 to 9.3 micron for Clara cells. Nuclear dimensions ranged from 7.5 micron in M3 to 4.0 micron in M1 and M2. Mucous cell M1 had electron-dense granules (1.5 micron in diameter); M2, electron-lucent granules (1.6 micron); M3, nucleated electron-lucent granules (0.51 micron); M4, cored granules (1.1 micron); serous (SC) and Clara cells (CC), electron-opaque granules (0.58 micron and 0.37 micron). The volume fraction of the cell occupied by granules was 63% in M1 and M2, M4 39%, SC 23%, CC 5%, and M3 4.5%. Smooth endoplasmic reticulum was observed only in M3 (33.8%) and CC (49%). Granular endoplasmic reticulum (GER) was most abundant in SC (21%) and least plentiful in M4 (2.2%). We conclude that mucous cells M3 and M4 and serous and Clara cells differ from each other and from M1 and M2 cells. Mucous cells M1 and M2 differ from each other only in amount of GER and secretory granule appearance.     

Mosaic characteristics of human endometrial epithelium in vitro: analysis of secretory markers and cell surface ultrastructure

Specific terminal carbohydrate structures and mucin-associated glycans increase in expression within the human endometrial epithelium during the secretory phase of the menstrual cycle but exhibit wide intercellular variation. We postulated that variation in glycosylation between cells would produce differences in the glycocalyx and result in complex mixtures of cells bearing different combinations of glycans. MUC-1 mucin, keratan sulphate and fucosylated lactosaminoglycans were examined in epithelial gland fragment cultures with antibodies (HMFG1, 5D4) and a lectin (Dolichos biflorus agglutinin). The glycocalyx was examined by transmission and high resolution scanning electron microscopy. The data were related to patterns of expression seen in vivo. The MUC-1 mucin was expressed relatively uniformly in culture, but heterogeneity was evident in mucin sialylation within the epithelial cell population. Double labelling of gland explant cultures for combinations of fucosylated lactosaminoglycans, keratan sulphate and MUC-1 demonstrated cells expressing all combinations of these markers. Ultrastructural examination confirmed remarkable intercellular variation in the glycocalyx. Though the human endometrial epithelium is relatively morphologically homogeneous, these observations reveal complex variations of cell surface glycosylation between neighbouring cells and suggest that secretory function might vary in a similar fashion.     

Cell dynamics in the olfactory epithelium of the tiger salamander: a morphometric analysis

Summary The factors controlling neurogenesis and differentiation of olfactory receptor cells in adults are poorly understood, although it is often stated that these cells undergo continual turnover after a pre-determined lifespan. An interesting model in which to study mechanisms which control olfactory receptor neurogenesis and cell turnover is the tiger salamander, since basal cell mitosis varies with epithelial thickness and location in the nasal cavity. This paper presents a quantitative light-microscopic study of the different cell types within the ventral olfactory epithelium of the tiger salamander using a computer-assisted morphometric analysis of 2 m sections. The results show that the surface density of olfactory vesicles remained constant throughout most of the epithelium and was independent of nasal cavity location, epithelial thickness and the total number of nuclei per unit epithelial surface area. Histological classification of nuclei into different cell types indicated that the increase in total cell number with epithelial thickness was mainly due to an increase in the number of immature receptor cells since the number of supporting cells varied only slightly and the numbers of basal cells and mature receptor cells remained constant except in the thinnest, most caudally located epithelium. It is concluded that the rate of maturation of receptor cells may be limited by an optimal surface density of olfactory vesicles. That is, when this density reaches 4.5×10⁴ vesicles per mm² there is a physical or chemical mechanism which prevents the final maturation of newly developing receptor cells, leading to their accumulation. This mechanism may also account for the variations in basal cell mitosis in this species.     

A simple technique for the isolation of rabbit endocervical epithelium

Summary A method is described for dissection of endocervical folds from adult rabbits, and subsequent collagenase dissociation of these folds, to yield both a single cell suspension (mostly stromal elements) and epithelial segments (retained on a monofilament mesh filter).     

Computer-assisted morphometric analysis for three-dimensional cell shape.

Quantitative, morphometric analysis of 3-dimensional cell shape may prove to be a valuable adjunct to scanning electron microscopy and to the evaluation of epithelial transport phenomena. Therefore, to facilitate the wider use of cell shape analysis, a computer-assisted technique has been developed to supplement or replace the usually tedious and otherwise limited manual techniques previously available. The computer programs described here have been designed to run in a small laboratory computer, do not require a large amount of operator time, and are shown to provide an accuracy and efficiency not practical with manual procedures.     

Ultrastructural analysis of thymic nurse cell epithelium

Thymic nurse cells (TNC), a paradigmatic cell type of cortical epithelium, are large lymphoid-epithelial cell complexes of thymocytes enclosed within vacuoles lined by the epithelial cell membrane. TNC express major histocompatibility complex (MHC) class I and class II molecules on their surface and vacuole-lining membranes at high density and it was suggested that TNC provide an optimal microenvironment for positive selection of T cells. In this report we present electron microscopical data demonstrating that chicken TNC display morphological structures of exocytosis previously shown for hormone-secreting cells. In TNC, however, exocytosis is restricted to the capillary cleft between the epithelial cell and engulfed thymocytes. Thus, besides physical contact between the epithelial cell and enclosed thymocytes, TNC may additionally influence the development of thymocytes through release of soluble factors in a restricted microenvironment. By employing the 3-(2,4-dinitroanilino)-3-amino-N-methyl-propylamine technique which at the ultrastructural level detects acidic organelles involved in processing of antigens presented by MHC class II molecules, we also show that TNC contain acidic compartments similar to classical antigen-presenting cells, i.e. early and late endosomes and lysosomes, albeit in a lower amount than in thymic dendritic cells. This fact provides evidence that TNC not only are capable of antigen presentation but also possess the intracellular machinery for antigen processing.     

Metachromasia of the endocervical epithelium in women treated with gonadotropin releasing hormone agonist

Endocervical epithelium from women treated with gonadotropin releasing hormone agonist (GnRH agonist) were compared with those from untreated women, using metachromatic stain with toluidine blue and immunohistochemistry, for estrogen and progesterone receptors. Smaller endocervical epithelium with lower intraepithelial mucus and more prominent nuclear distribution of estrogen receptors were seen in a woman who was treated for twelve months with GnRH agonists, as compared with those from an untreated premenopausal woman.     

Atypical meningioma: morphometric analysis of nuclear pleomorphism

The revised edition of the WHO classification of brain tumours now includes the "atypical" meningioma (grade II) which should be placed between the common type (grade I) and anaplastic type (grade III) according to histomorphological features and prognosis. However, diagnostic criteria for atypical meningioma are vague and the significance of brain invasion in the determination of malignancy is controversial. Nuclear pleomorphism and mitoses are usually considered the most important parameters to distinguish atypical and malignant meningiomas. According to WHO classification we selected eight cases of meningioma diagnosed as atypical (3 cases) and malignant (5 cases). All the tumours were supratentorially located. Nine cases of benign meningiomas were also studied as a control group. Morphometrical analysis was carried out by S.A.M. (Shape Analytical Morphometry) system. S.A.M. logical architecture assumes that each irregular shape contains elements of two distinct logical domains: gross distortions that interest the contour and its local perturbations. These features were investigated separately by analytical procedures to acquire independent parameters both on the logical and the numerical level. The results, statistically evaluated, show that nuclear pleomorphism is not a satisfactory criterion, if used alone, to distinguish atypical from malignant meningioma (Discriminant Analysis: 19% of minimum error).     

Factors of osteogenesis and the secretory function of transitional epithelium

Summary The author conducted an experimental, histogenetic and histochemical analysis of the transitional epithelium bone-forming activity in the transplantates and in conditions of ligature of the renal blood vessels. It was demonstrated that in such conditions substances of polysaccharide origin are secreted by the epithelium into the underlying tissue, as well as over the surface of the epithelium layer. It is suggested to name this secretion pelvin. The introduction of pelvin in the connective tissue causes the appearance of myeloid hemopoiesis in it. A hypothesis is put forward of the presence of the incretory function in the transitional epithelium. The explanation of its bone-forming activity in experimental conditions is suggested.Presented by Active Member of the AMN SSSR G. V. Vygodchikov     

Immunoreactivity to desmin in secretory epithelium of eccrine sweat glands

The finding of immunoreactivity to desmin in eccrine sweat glands is reported. Two monoclonal anti-desmin antibodies of the same clone (33) produced a distinct positivity in the secretory cells of the sweat glands in 15/16 biopsies. No immunoreactivity for desmin was found in control sections from apocrine sweat glands, salivary, mammary, prostate and lacrimal glands.     

Ultrastructural features of secretory cells in the bovine oviduct epithelium

The non-ciliated (NC) cells of the bovine oviduct epithelium, have been shown to release embryotrophic substances to the oviduct lumen. The aim of the present study was to investigate the ultrastructure, focusing on aspects of the secretory machinery, of NC cells in different segments of the oviduct during and after transoviduct migration of zygotes and embryos. Dairy heifers (n=8) were superovulated with an ECG/cloprostenol regimen, and the time of ovulation was estimated by ultrasound scanning. Samples from the infundibulum, ampulla, isthmus and uterotubal-junction of the oviduct were surgically collected from animals at 19–96 h and 7 1/2; –8 1/2 days after ovulation and processed for transmission electron microscopy, following standard procedures. The NC cells contained characteristic membrane-bound secretory granules composed of a lamellar cortex encaging an amorphous medulla. The two components could still be recognized during extrusion of the granule content into the oviduct lumen by exocytosis. During granulogenesis, small maturing granules without the lamellar structure were observed, but distinct condensing vacuoles were absent. An abundance of granules was found in the early versus the late group. In both groups the uterotubual junction was almost free of granules. This segment, on the contrary, was characterized by the presence of primary and secondary lysosome-like bodies. In the early group the intracellular location of the granules varied between oviduct segments. In the infundibulum they were placed in the supranuclear cytoplasm, in the isthmus they were found in the most apical part of the cells, while in the ampulla an intermediate granule position was noticed. In both groups the uterotubal junction was almost free of granules. This segment, on the contrary, was characterized by the presence of primary and secondary lysosome-like bodies. Cytoplasmic protrusions, often containing nuclei, were more frequent in the late than in the early group. This phenomenon may represent epithelial renewal. In conclusion, the NC cell of the bovine oviduct epithelium possesses an extensive capacity for protein synthesis and secretion. The numbers and location of secretory granules show cyclic and segmental variations. Most granules are present in the infundibulum and ampulla during the period of transoviduct migration of zygote and embryo.     

Analysis of cell populations of normal and injured mouse lens epithelium. I. Cell cycle

Using a combination of single isotope and double isotope autoradiography after injection of ³H-thymidine and of ³H- + ¹⁴C-thymidine, respectively, the cell cycle of normal and injured lens epithelial cells in the mouse was determined. Progenitor cells in the peripheral region of normal lens epithelium were found to traverse the replicative cycle in the same amount of time as the injury-stimulated cells in both peripheral and central (wound) regions. The individual phases were also the same length, except for a slight shortening of G₂ in the injured epithelium. The durations of the phases were: S: 11–12 hours; G₂: 1.5–2 hours; M: 4.2–5 hours; G₁ (derived): 38–44 hours; and total cycle: 55–61 hours. Two findings were significant in view of previous observations that injury to mouse lens seldom induces lens opacity. First, while the cell cycle duration was not affected by injury, a burst of proliferation of potentially active cells ensued. And, secondly, this burst of proliferation involved only one cell cycle. Only a small number of cells, equivalent to the normal progenitor compartment, continued into a second replicative cycle. The wound was healed, therefore, mainly by one division cycle involving a large number of cells.     

Nonolfactory surface epithelium of the nasal cavity of the bonnet monkey: A morphologic and morphometric study of the transitional and respiratory epithelium

The purpose of the present study was to characterize ultrastructurally the nonolfactory nasal epithelium of a nonhuman primate, the bonnet monkey. Nasal cavities from eight subadult bonnet monkeys were processed for light microscopy, and scanning and transmission electron microscopy. Nonolfactory epithelium covered the majority of the nasal cavity and consisted of squamous (SE), transitional (TE), and respiratory epithelium (RE). Stratified SE covered septal and lateral walls of the nasal vestibule, while ciliated pseudostratified RE covered most of the remaining nasal cavity. Stratified, nonciliated TE was present betwen SE and RE in the anterior nasal cavity. This epithelium was distinct from the other epithelial populations in abundance and types of cells present. TE was composed of lumenal nonciliated cuboidal cells, goblet cells, small mucous granule (SMG) cells, and basal cells, while RE contained ciliated cells, goblet cells, SMG cells, basal cells, and cells with intracytoplasmic lumina lined by cilia and microvilli. TE and RE contained similar numbers of total epithelial cells and basal cells per millimeter of basal lamina. TE was composed of more SMG cells but fewer goblet cells compared to RE. We conclude that nonolfactory nasal epithelium in the bonnet monkey is complex with distinct regional epithelial populations which must be recognized before pathologic changes within this tissue can be assessed adequately.     

Maturation of myocardial capillaries in the fetal and neonatal rat: An ultrastructural study with a morphometric analysis of the vesicle populations

The ultrastructural morphology of the cellular and extracellular components of the developing myocardial capillary wall—from the 16-day-gestation fetus of the rat to the 21-day neonate—was examined. A morphometric analysis of plasmalemmal vesicles and of coated vesicles and pits of capillary endothelial cells was performed during the same developmental period. As the lateral extensions of the capillary endothelial cells change from irregular to regular in their thickness during development, there is an increase in the number of plasmalemmal vesicles and a progression from clusters of plasmalemmal vesicles to a uniform distribution in the endothelial cell. The ratio of vesicles which are open to the luminal front, which are “free” in the cytoplasm, or which are open to the abluminal front of the endothelial cell was consistent throughout development. The numerical density of plasmalemmal vesicles demonstrates a gradual and significant increase. In contrast, the numbers of coated vesicles and pits are variable within a very narrow range, and no pattern of increase or decrease is discernible during development. Similarly, there is no change in interendothelial cell junctions, which consist of occluding and primitive adhesive junctional types, during development. The lamina densa of the basal lamina gradually develops from discontinuous, patchy densities along the abluminal surface of the endothelial cells to a continuous and distinct layer by 21 days gestation. The presence of the proteoglycan species in the developing basal lamina was assessed with the cationic dye ruthenium red (RR), and the appearance of RR-marked proteoglycans was found to parallel the appearance of lamina densa material. The RR sites appear discontinuously in patches; and later, the RR sites appear in a continuous and regular planar lattice in the lamina rara interna and externa at 21 days gestation. A complete array of RR-stainable anionic sites outside a continuous lamina densa near birth indicates that the basal laminae of developing capillaries in the heart are morphologically, and in part biochemically, mature by the end of the first neonatal week. Our results show that the endothelial cells and the subtending basal lamina of myocardial capillaries gradually mature morphologically during the final days of gestation and the first neonatal week. The finding of tight junctions and small areas of vesicle concentration in fetal endothelial cells could indicate that sites of permeability are limited early in myocardial capillary development and that these vesicular sites increase as gestation proceeds and as the myocardial capillaries mature.