The ultrastructure of the rat esophageal epithelium during ontogenesis]

The development of the epithelium of the rat esophagus was examined continuously from the 13th day post-conception until one day post-partum. Besides the single-results at different phases of development the knowledge, that the esophageal ontogeny of different mammalians may be considerably different, is of special importance. To this matter of fact was not paid attention in present literature, but the authors accentuate common things. The significant results during development are the following: 1. The completely undifferentiated epithelium of the 13th day at the same time develops basement-membrane and basic membrane of the cytoplasm. The organelles are under construction. Centriols in cells near to the lumen are seen in connection to the single-cilia, which occur till the 17th day of ontogeny. These essentially differ from cilia of the ciliated epithelium. 2. The cylindrical epithelium constitutes until the 16th day. Afterwards the first synthetic productivity like organisation of filaments are observed. By that superficial cells loose their capacity to divide. 3. On the 17th day intercellular spaces between neighbouring cells at the lumen abruptly rip up. In loco cylindrical cells change to squamous cells. There are no essential differences in time between cranial and caudal parts of the esophagus which proofs an entodermal genesis of the epithelium. 4. Changes in the ultrastructure at about 19 days p.c. cause the epithelium's keratinization. 5. 21 days p.c. few cilia-bearing cells scattered between the cells in keratinization are to be seen. 6. Before birth superficial cells become separated and are shed from the surface completely post-partum.     

The development of the guinea pig gallbladder epithelial cells. I. Light microscopical and carbohydrate-histochemical investigations (author's transl)]

The development of the guinea pig gallbladder epithelium was studied from the 19th day of intrauterine life to the 31st postnatal day by means of histological and histochemical staining reactions. At first, the epithelium is a columnar pseudostratified one. Its transformation into a simple columnar eptihelium is terminated by the 31st day of the intrauterine life. Then the epithelial cells become more columnar and their nuclei acquire a basal position. Somewhat later the epithelium invaginates the underlying mesenchyme. Up to the 57th day the epithelium contains much glycogen. Neutral and carboxylated mucosubstances are demonstrable after the 30th day. From the 48th day onwards sulphated mucosubstances can be visualized in some cells in the depth of the invaginations and from the 51st day in the epithelial cells of the gallbladder. "Light" mucoid cells appear first in the epithelium of day 58. After the 6th postnatal day the "light" cells are rarely seen in the invaginations. The development of the gallbladder epithelium is completed about the 10th postnatal day. The epithelial mucosubstances of the gallbladder of the adult animal could be classified as GC- mucins and S-mucinsA, 1.0 MgCl2.     

Rebuilding of rat intestinal mucous epithelium in prenatal ontogenesis

Morphological differentiation of the intestinal epithelium in the laboratory rat occurs between the 16th and 21st day of prenatal development. The pseudostratified epithelium is rebuilt into simple epithelium of the future lining. A characteristic sign of this rebuilding is formation of primitive folds, villi and intraepithelial vacuoles corresponding in submicroscopic picture with a secondary luminization. On the tips of folds and villi groups of cells released from the epithelium are observed. In these cells expression of activated caspase-3 confirms the presence of apoptosis in the process of cell death during epithelium rebuilding.     

Postnatal changes in the ultrastructure of the rat olfactory epithelium: the supranuclear region of the supporting cells

Summary The present electron-microscopical study reports ultrastructural changes occurring in the supranuclear region of the supporting cells of the rat olfactory epithelium during the first 16 days of postnatal life. These changes are concerned with the enclosure of receptor cell dendrites and an increase in the amount of smooth endoplasmic reticulum, which has a specific distribution in the supporting cell. An increase in microvillous projections at the free cell surface is also observed. Moreover, this report demonstrates that the cytoarchitecture of the apical portion of the olfactory epithelium at the 16th day of postnatal life is similar, with respect to the relationship between supporting cells and receptor cell dendrites, to that of adult animals.     

The effects of adrenalectomy and hydrocortisone replacement on the thyriod of the adult male rat I. Morphometrical data and histochemistry of some oxidative enzymes.

Morphometrical and histochemical studies were performed to determine the effects of adrenalectomy and hydrocortisone replacement on the rat thyroid. It follows from the performed studies that morphometrical and histochemical changes in the rat thyroid induced by adrenalectomy or hydrocortisone replacement depend upon the duration of the experiment. From the 4th day of the experiment adrenalectomy results in an increase in the volume fraction of the epithelium of the thyroid vesicles with a concomitant decrease of the colloid fraction. As compared to sham operated animals on the 10th day of the experiment the increase in the height of the epithelial cells was seen. Hydrocortisone replacement partially prevents the thyroid changes induced by adrenalectomy, however, this hormone markedly increases the volume fraction of the thyroid stroma and the height of the epithelial cells. On the other hand, histochemical reactions for various oxido-reductases do not provide helpful information for evaluation of the secretory activity of the rat thyroid. It follows from our results that adrenalectomy enhances thyroid stimulation by TSH and enhances the secretory activity of this gland, effects partially prevented by hydrocortisone replacement.     

Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

Summary The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Zinc deficiency in the 11 day rat embryo: a scanning and transmission electron microscope study

Zinc deficient rat embryos were obtained on the 11th day of pregnancy and examined by scanning and transmission electron microscopy. Scanning electron microscopy revealed an increase in the number of deformed embryos, as well as embryonic growth retardation. In addition, the epithelium of zinc deficient embryos displayed a marked increase in surface microvilli, as well as the presence of blebbing. Transmission electron microscopy indicated extensive cell death in the neural epithelium which was apparently more severely damaged by zinc deficiency than were mesenchymal cells. Mitochondrial cristae were affected to a greater degree than any other membrane of the cell and cristael disintigration appeared to represent the principal cellular lesion preceding necrosis of neural cells and neural tube teratology.     

Differentiation of the müllerian (paramesonephric) duct epithelium in the rat

Differentiation of the Müllerian duct epithelium was studied in 15- to 21-day female rat foetuses. The proximal segment of the Müllerian duct is formed by the 15th day; it runs parallel to the Wolffian duct and the two are wrapped in a common basement membrane. On the 16th day the genital ducts are clearly separate; the Müllerian duct has a slit-like lumen and is lined with simple columnar epithelium. Throughout the whole of the given period the epithelium retains a relatively indifferent appearance. Characteristic findings from the 18th day include the apical migration of centrioles and the formation of solitary cilia.     

Immunocytochemical observation of paraquat-induced alveolitis with special reference to class II MHC antigens.

The expression of class II major histocompatibility complex (MHC) antigens on alveolar epithelial cells and macrophages was investigated immunocytochemically in paraquat-induced alveolitis in the rat lung. Until 2 days after paraquat injection, class II MHC antigens were expressed on the type II alveolar epithelium without any inflammatory cellular infiltration. From the 4th to the 7th day after paraquat injection, class II MHC antigen-positive macrophages increased in the alveolar spaces, whereas the expression on the type II alveolar epithelium became obscure. Over 10 days after the injection, interstitial fibrosis progressed and the intra-alveolar inflammatory infiltrates decreased. Epithelial cells lining the thickened fibrous septa no longer expressed class II MHC antigens. These results suggest that chemical stimuli can induce class II MHC antigen expression on the type II alveolar epithelium in the early stage of cellular injury, followed by inflammatory infiltration and interstitial fibrosis.     

Immunocytochemical observation of paraquat-induced alveolitis with special reference to class II MHC antigens

The expression of class II major histocompatibility complex (MHC) antigens on alveolar epithelial cells and macrophages was investigated immunocytochemically in paraquat-induced alveolitis in the rat lung. Until 2 days after paraquat injection, class II MHC antigens were expressed on the type II alveolar epithelium without any inflammatory cellular infiltration. From the 4th to the 7th day after paraquat injection, class II MHC antigen-positive macrophages increased in the alveolar spaces, whereas the expression on the type II alveolar epithelium became obscure. Over 10 days after the injection, interstitial fibrosis progressed and the intra-alveolar inflammatory infiltrates decreased. Epithelial cells lining the thickened fibrous septa no longer expressed class II MHC antigens. These results suggest that chemical stimuli can induce class II MHC antigen expression on the type II alveolar epithelium in the early stage of cellular injury, followed by inflammatory infiltration and interstitial fibrosis.     

Light and electron microscopic studies on the development of the spiral prominence of the cochlear duct of the fetal guinea pig

The anlage of the spiral prominence can be seen on the 37th day of development as a small protrusion of the epithelium towards the lumen of the cochlear duct. During the further progress, the spiral prominence more distinctly protrudes by augmentation of the vascularized connective tissue. In the epithelial cells pinocytotic vesicles near the plasmalemma are seen earliest lateral and basal on the 37th day, apical on the 39th day. The epithelial cells send basal cytoplasmic extensions towards the connective tissue. Starting on the 44th day, small invaginations of connective tissue extend into the epithelium, remaining separated from the epithelial cells by the basal lamina. Until the 48th day, the monostratified epithelium remains columnar, thereafter it changes to cuboidal or flat. Towards the end of the development, the invaginations of the connective tissue nearly reach the surface of the epithelium, being separated from the endolymph by a small epithelial area.     

Morphogenesis of rat lingual filiform papillae.

The morphogenesis of filiform papillae on rat tongue was investigated with the electron microscope. Tongue rudiments were first seen on the 12th day of gestation. At 15-17 days, dermal papillae had formed and were arranged in hexagonal array on the dorsal lingual surface. Capping each dermal papilla was a two-layered epithelium that protruded slightly above the lingual surface, thus forming the early filiform papilla. In the next stage of development, at 18-19 days of gestation, the epithelium lining the papilla had differentiated into two cell populations, one producing hard keratin, the other producing soft keratin. Some of the keratinized epithelial cells assumed a position at an acute angle to the tongue surface and extended deep into the epithelium. In the next stage, 20-21 days, a cleft appeared within these angularly oriented cells. This resulted in the division of the epithelium into keraatin-lined individual filiform papillae. Finally, the individual papillae increased in size to the adult form.     

The development of the guinea pig gallbladder epithelial cells. II. Electron microscopical and enzymhistochemical investigations (author's transl)]

The development of the guinea pig gallbladder epithelium follows a distinct time schedule. During the first phase (up to 30th day of intrauterine life) the epithelial cells increase in number. They remain small and undifferentiated. In the second phase, from the 30th to the 44th day, cytodifferentiation is a dominating feature. The epithelial cells increase in height, the nuclei become more basal, the cells acquire their final zonal structure and the cell organelles exhibit their characteeristic appearance. Weak enzyme activities can be observed. In the third phase, from the 45th day until birth, there is functional differentiation and the adult pattern of enzyme distribution is established. Glycogen appears first on day 29, increases in amount and then disappears by day 57. There is a marked development of the Golgi apparatus associated with increased synthesis of secretory material. Between the 59th embryonic day and the 6th day of life mucoid cells with different functional states appear in the gallbladder epithelium. Later on these cells can be visualized only in the depths of the invaginations. After birth the epithelial cells become more columnar and by 10 days after birth the adult appearance of the epithelium is fully established.     

扬子鳄胚胎背腺的发生及退化

本文在１４例扬子鳄Ａｌｌｉｇａｔｏｒｓｉｎｅｎｓｉｓ胚胎中观察了背腺的发生及退化过程。孵化第２８天,背中线左右两侧第二行鳞片处的表皮内陷形成实心的背腺腺芽;第３８天,背腺腺泡明显,腺上皮为复层上皮;从第４６天开始,腺上皮出现明显的退化,大量增殖的腺管上皮细胞逐渐堵塞腺管及腺孔。扫描电镜观察表明,孵化第３２—３６天的胚胎背部第二行鳞的各列鳞片表面均有背腺腺孔,以后逐渐出现少数不规则的退化,孵化第５８天以后,绝大多数背腺腺孔消失。对扬子鳄背腺的发生及退化现象作了讨论。     

小鼠胚胎发育过程中表皮生长因子受体的免疫荧光定位研究

用间接免疫荧光法研究了第12—19天小鼠胚胎的表皮生长因子受体(EGFR)在各种组织中的分布。结果表明,特异性荧光出现在EGFR阳性细胞的细胞膜上。第14.5天鼠胚鼻粘膜上皮首先显示很强的EGFR特异性荧光,此后荧光稍为减弱,直至第19天后消失。消化系统中,舌味觉上皮在第16天、胃粘膜上皮在第17—18天间、十二指肠上皮在第17.5—18.5天、直肠粘膜上皮在第15.5—16天和肛管粘膜上皮在第15天均显示强特异性荧光。肝细胞从第14.5天起有弱阳性反应,随胎龄增大强度缓慢地增强。此外,在胚胎发育不同时期,还看到若干组织呈现阳性反应,包括膀胱粘膜变移上皮、眼睑原基、腺垂体上皮、舌下腺腺泡细胞、附属腺上皮细胞、胰岛细胞、颌下腺腺上皮和导管上皮细胞、降主动脉内皮以及卵巢髓质部富含血管的疏松结缔组织中的成纤维细胞等。     

Ultrastructural differentiation of glandular stomach (proventriculus) in chick embryo

Cytochemical characterization of mucosubstances of chick glanular stomach (proventriculus) changes from 15 days of development to postnatal and adult stages was studied. To corroborate these data cytochemical, ultrastructural and ultracytochemical study of chick embryo proventriculus from 7 to 20 days of development was performed. At the 7th day several layers of undifferentiated cells formed an epithelium which covered the walls of the glandular stomach. Mocosubstances were not found. Between the 9th and 5th day a single layer of cylindrical cells was encountered forming invaginations which originated deep glands. Three types of cells were separated from the above mentioned layer, dark, clear and undifferentiated. The dark cells had organelles which are involved in protein synthesis and the clear ones were rich in mitochondria. Argentaffine cells appeared at 15th day instead mucosubstances formed a thin coat on the epithelium at 9th day which increased at the end of development in the apical cytoplasm and gland cells. These observations demonstrate that proventriculus of chick embryo has ultrastructurally differentiated cells involved with enzymatic and hydrochloric acid secretion after the 9th day. These progressive events are correlated with the digestion process of yolk during embryogenesis. At the end of development the proventriculus has completely organized the glandular layer.     

Endocrine cells of stomach epithelium in the ontogenesis of albino rats

By means of the light and electron microscopy methods structural bases of differentiation and contents of endocrine cells of the stomach epithelium have been studied during the white rat pre- and postnatal development. The development of the endocrine epithelial cells occurs in parallel with the exocrinic ones. Endocrine EC-, G-, D-, P-cells are the first to be revealed in composition of the embryonal stomach epithelium, the others--during the early postembryonic period. The differentiation of the endocrine cells is characterized with asynchronism, is accompanied with a gradual development of organells, increasing amount of secretory granules and appearance of polarity in their distribution. By the 30th day of the postnatal development, the amount of the endocrine cells in the stomach epithelium increases by 5 times in comparison to those in the 1-day-old animals, with simultaneous reaching of the high level in specific differentiation.     

Origin of the brushborder in the differentiating midgut of Melasoma saliceti (Chrysomelidae, Coleoptera) embryos

The embryonic development of Melasoma saliceti takes eight days at room temperature. At the beginning of the 5th day the endoderm cells have already formed a unilayered epithelium of the midgut primordium. The midgut epithelium is formed by flat cells that are not connected by specialized intercellular junctions. Large vesicles can be seen in dilated intercellular spaces of the epithelium. Cytoplasmic projections, similar to microvilli, appear in the vesicles. During the 5th day ofdevelopment, the vesicles grow and become enclosed by the intercellular junctions of a zonula adherens type. During the 6th day of development the cell junctions surrounding the vesicles become transformed into a septate type. On the 8th day of development the vesicles come close to the apical sides of the midgut cells and open towards the yolk. At the same time the microvilli spread over the apical surface of the midgut primordium to form the regular brushborder of the larval midgut. In the species studied the vesicles appear to "prefabricate" the apical surfaces of the future midgut epithelium.     

Distribution of histamine in the rat kidney during pregnancy and development

Summary An antiserum against conjugated histamine and two oligonucleotide probes that detect the mRNA encoding L-histidine decarboxylase (HDC) involved in histamine synthesis were used to study the appearance of histamine and its location in the kidneys of fetal, newborn and young postnatal rats and in the kidneys of pregnant rats. On embryonic days 16 and 18 (E16 and E18), some HA-immunoreactive (HA-ir) cells were found within the largest S-shaped bodies. Histamine was found to appear rapidly between the 18th and 20th embryonic days in the convoluted tubules of the kidneys. On postnatal day 0 (P0), the distal convoluted tubules and collecting ducts exhibited bright fluorescence, the intensity of which decreased quickly so that it was faint on day P4 and absent at later stages. In kidneys of pregnant rats HA-ir was found in the epithelium of both the Bowman's capsule, collecting ducts and in a few cells within the tubules. Nonuniform HA-ir was also detected within glomeruli. No evidence for the presence of L-histidine decarboxylase mRNA in kidneys of fetuses or pregnant rats was seen. It is concluded that distinct structures in the developing rat kidney contain histamine during a period around birth from day E20 to day P4. In the pregnant rat, the epithelium that is in direct contact with the urine flow is immunoreactive for histamine from day 16 to 20 of pregnancy. The results suggest that histamine is not synthesized locally in the kidneys but rather originates from other tissues.