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PubMed1987

[Changes in the expression of prekeratins with molecular weight of 55 and 40 kD in monolayer epithelium during skin morphogenesis in rats].

It has been shown by indirect immunofluorescence using monoclonal antibodies against adult rat simple epithelial prekeratins with the molecular weight of 55 kD (PK55) and 40 kD (PK40) that PK55 was expressed in the covering ectoderm until the 11th day of the antenatal period. PK55 expression markedly increased in ectodermal cells lining the heart region, with PK40 appearing in the same cells on day 11. Beginning from the 16th day gradual loss of both prekeratins started with the parallel formation of squamous differentiated epidermis. These proteins were retained in the outer layers of peridermal cells and in some cells of the basal layer (probably Merkel cells). PK55 was re-expressed on the 18th day in cells migrating into dermal layer during hair folliculi formation. PK55 disappeared again in mature folliculi. Thus, a correlation between distinct morphogenetic events and PK55 and PK40 expression has been found.

Animals↗

PubMed1989

Ornithine aminotransferase distribution in ocular tissues and retinas of cat and mouse.

Ornithine aminotransferase (OAT), a mitochondrial matrix enzyme, is genetically deficient in patients with gyrate atrophy of the choroid and retina. Histologically defined micro-samples (10 ng-6.8 micrograms dry weight) were dissected out from freeze-dried tissue sections of eyeballs of cat and mouse, and the OAT activities were determined by a newly developed microassay method in the ocular tissues and retinal layers. Very high specific activities of OAT, expressed on a dry weight basis, were found in the feline ocular tissues of ectodermal origin, that is, neuroretina, retinal pigment epithelium, ciliary processes and epithelium of iris. In cat and mouse retinas, high OAT activities were distributed in the inner retina with an activity peak in the inner plexiform and ganglion cell layers. Very low activity was present in the outer nuclear layer. The inner segments of photoreceptor cells, which are very rich in mitochondria, contained the highest OAT activity. In contrast, the outer segments of photoreceptor cells contained the low activity resulting from contamination by small pieces of inner segments.

Animals↗

PubMed1990

Histochemical localization of transforming growth factor-beta 1 in developing rat molars using antibodies to different epitopes.

In this study transforming growth factor-beta 1 (TGF-beta 1) has been immunolocalized in developing rat molars using two well characterized polyclonal antibodies, Anti-CC and Anti-LC, that recognize extracellular and intracellular TGF-beta 1, respectively. With immunohistochemical methods and the ABC-peroxidase system of detection, the growth factor was immunolocalized within the ectodermally derived enamel organ and the neural crest-derived dental papilla at the early and advanced bell stages of development. With Anti-CC, widespread and abundant extracellular TGF-beta 1 was found associated with the stellate reticulum and within central and apical regions of dental papilla mesenchyme. In contrast, Anti-LC localized TGF-beta 1 intensely within the cells of the outer dental epithelium. Moderate immunostaining for TGF-beta 1 with Anti-LC was also evident within the apical cytoplasm of inner dental epithelial cells and odontoblasts. These findings support the hypothesis that TGF-beta 1 may play a paracrine role in tooth development by regulating the epithelial-mesenchymal interactions that influence growth and cytodifferentiation events.

Animals↗

PubMed1986

Ultrastructure of the dental epithelium during enameloid mineralization in a teleost fish, Cichlasoma cyanoguttatum.

Secretory-stage inner dental epithelial cells (IDE) of tooth buds deposited an unmineralized, ectodermally-derived, enameloid collagen matrix. Pharyngeal plates bearing tooth buds were fixed: some were demineralized, others treated with guanidine-EDTA, then fixed and post-fixed in osmium tetroxide with potassium ferricyanide. Thin Epon sections were viewed in a Jeol 100B TEM. Nascent enameloid crystals were orientated parallel to the collagen fibres and attained widths of 200 nm. Enameloid collagen was absent in demineralized mature enameloid. The outer dental epithelial plasma membrane was deeply invaginated forming extensive channels associated with elongated fuzzy-coated vesicles. Four configurations of IDE cells were characterized by cellular constituents, including elongated granules, Golgi complexes, multivesicular bodies, large electron-dense granules and extracellular amorphous material which was also adjacent to cells containing few organelles associated with protein synthesis, within infoldings of ruffled apical membranes and multivesicular bodies. This material was considered to be resorbed enameloid collagen, not a secretory product.

Amelogenesis↗

PubMed1989

Insulin-like growth factor II may play a local role in the regulation of ocular size.

The ultimate size and shape of the eye has a profound influence on its refraction and function. However, the role of growth factors in normal ocular development is poorly understood. Insulin-like growth factors IGF-I and -II have major effects on cell growth and differentiation in tissue culture. Recently their importance for in vivo development has been studied; IGF-II is predominant prenatally, with a probable local role in the differentiation of some mesodermally derived tissues. Ocular development and size is partially dictated by the condensation of the outer collagenous scleral coat (the 'white') of the eye from orbital mesoderm. We investigated IGF-II expression and IGF-II receptor distribution during normal ocular development in the mouse fetus using in situ hybridization and immunohistochemistry. IGF-II mRNA was expressed by the loose mesenchymal orbital tissue as it differentiated to form the sclera, but not in the compact mature sclera or cornea, or in the ectodermally derived retina or skin. IGF-II gene expression was seen in the orbit at E14, reached a peak just before parturition and then declined to background levels after birth. Similarly, type 2 IGF receptors were shown with immunohistochemistry to be present on developing scleral cells and to be modulated in parallel with IGF-II mRNA expression. We suggest the IGF-II expression by differentiating cells that compact to form the collagenous ocular coat plays a local role in determining the ultimate shape and size of the developing eye.

Animals↗

PubMed1978

In vitro development of inner cell masses isolated immunosurgically from mouse blastocysts. I. Inner cell masses from 3.5-day p.c. blastocysts incubated for 24 h before immunosurgery.

This paper describes the in vitro development of inner cell masses isolated immunosurgically from mouse blastocysts which had been collected on 3.5 days p.c. and then incubated for 24 h. The inner cell masses continue to grow in culture and develop through a series of stages with increasing complexity of internal organization. By day 1 all of the cultured ICMs have an outer layer of endoderm, and by day 3 some of them have two distinct kinds of inside cells; a columnar epithelial layer and a thin hemisphere of elongated cells. Later, mesodermal cells appear to delaminate from a limited region of the columnar layer, close to where it forms a junction with the thinner cells. By day 5, about 25% of the cultured ICMs have a striking resemblance to normal 7.5-day p.c. C3H embryos, with embryonic ectoderm, extra-embryonic ectoderm and chorion, embryonic and extra-embryonic mesoderm, and visceral endoderm. When mechanically disrupted and grown as attached clumps of cells in a tissue dish, these embryo-like structures give rise to trophoblast-like giant cells. These results suggest that the inner cell mass of 4.5-day p.c. blastocysts contains cells which can give rise to trophoblast derivates in culture.

Animals↗

PubMed1990

Ontogeny of basic fibroblast growth factor binding sites in mouse ocular tissues.

Basic fibroblast growth factor (bFGF) binding to ocular tissues has been studied by autoradiographical and biochemical approaches directly performed on sections during mouse embryonic and postnatal development. Frozen sections of embryos (9 to 18 days), newborns, and adults (1 day to 6 months) were incubated with iodinated bFGF. One specific FGF binding site (KD = 2.5 nM) is colocalized with heparan sulfate proteoglycans of the basement membranes and is heparitinase sensitive. It first appears at Day 9 around the neural tube, the optic vesicles, and below the head ectoderm and by Day 14 of embryonic development is found in all basement membranes of the eye. At Day 16, very intensely labeled patches appear, corresponding to mast cells which have been characterized by metachromatic staining of their heparin-rich granulations with toluidine blue. In addition to the latter binding, we have also observed a general diffuse distribution of silver grains on all tissues and preferentially in the ecto- and neuroectodermic tissues. From Days 17-18, there is heterogeneous labeling inside the retina, localized in the pigmented epithelium and in three different layers colocalized with the inner and outer plexiform layers and with the inner segments of the photoreceptors. This binding is heparitinase resistant but N-glycanase sensitive and may represent a second specific binding site corresponding to cellular FGF receptors (KD = 280 pM). Both types of binding patterns observed suggest a significant role for bFGF in eye development and physiology.

Animals↗

PubMedDate not supplied

Epidermoid cysts of the cranial bones.

Ectodermally derived tissue in ectopic sites is seen in the head and neck. Extracranial dermoid and epidermoid tumors are relatively rare. While most otolaryngologists are familiar with the cholesteatoma of the otic area, not very many are exposed to this lesion in other sites. Those of the cranial bones are even rarer still. These tumors may expand (1) laterally in the cranial bones, (2) externally to present as masses in the scalp or facial region, or (3) internally to involve the intracranial contents. A patient with a frontal bone epidermoid, whose tumor had expanded in all three directions to erode both inner and outer cortex of cranium and laterally to rupture into the frontal sinus, is discussed. The literature is reviewed and the management of these rare masses is discussed.

Adult↗

PubMed1989

Electron microscopic studies on primary mesenchyme cell ingression and gastrulation in relation to vegetal pole cell behavior in sea urchin embryos.

Early morphogenetic events of primary mesenchyme cell (PMC) ingression and gastrulation were examined by scanning and transmission electron microscopy, with special attention directed to changes in the shape of vegetal pole cells, the length of their microvilli, and interactions between microvilli and the hyaline layer (HL). Eight cells (vegetal pole cells) with elongated microvilli remained in the vegetal pole region while surrounding cells ingressed into the blastocoel to form the primary mesenchyme. These vegetal pole cells indented with the surrounding cells at the stage of gastrulation. The outer surface area with elongated microvilli of vegetal pole cells expanded at the stage of PMC ingression, but was considerably reduced at gastrulation. Microvilli on vegetal pole cells continued to adhere to the HL up to the stage of PMC ingression, but ceased to do so at the time of gastrulation. Thus, the area with separated HL, which is restricted to the region of the PMC released at the stage of PMC ingression, spreads almost entirely throughout the area of the indenting vegetal plate at gastrulation. The apical lamina, apparently consisting of fibrous material intertwinning the stalks of the microvilli, filled the space between the HL and ectodermal cells. The cells surrounding those of the vegetal pole and indenting with those at the stage of gastrulation appeared to behave in the same way as ingressing PMCs in both cell-shape and loss of adhesion of microvilli to HL. The role of vegetal pole cells in early morphogenetic events is discussed.

Animals↗

PubMed1989

Transforming growth factor alpha and its receptor in neural retina.

Transforming growth factor alpha (TGF-alpha) stimulates mitosis of many ectodermal cells but has not previously been studied for its role in neural tissues such as retina. We examined bovine retina for the presence of TGF-alpha mRNA, TGF-alpha protein and for the presence and location of the TGF-alpha/EGF receptor. Biochemical studies demonstrated a high level (770 fmol/mg protein) of specific, high affinity (Kd = 2 nM) TGF-alpha/EGF receptors in membrane homogenates of neural retina, but undetectable binding to homogenates of retinal pigment epithelium. Light microscopic autoradiograms of sections of neural retinal tissue incubated with 125I-EGF indicated that specific TGF-alpha/EGF receptors were present on one or more cell types of the retina with the exception of the outer segments of the photoreceptor cells. In addition, retinal cells appear to synthesize TGF-alpha since both mRNA for TGF-alpha and TGF-alpha protein (4.2 ng/mg protein) were detected in retinal extracts using cDNA hybridization and TGF-alpha RIA techniques. The role(s) of TGF-alpha and its receptor in retina is unknown, but it is possible that they interact via an autocrine/paracrine mechanism to influence retinal regeneration, proliferative retinopathies or neural transmission.

Animals↗

PubMed1978

Cellular morphology and architecture during early morphogenesis of the ascidian egg: an SEM study.

1. Cellular morphology and architecture during early morphogenesis of the ascidian embryo were examined by SEM. 2. The outer surface of the embryo was essentially smooth. The blastocoel could be seen in the dissected blastula. On the cell surface bordering the blastocoel, numerous pseudopodia extended from cells onto adjacent cells. These pseudopodia were suggested to contribute to cell-to-cell adhesion. 3. Before the initiation of gastrulation, a layer of the cells of the animal (ventral) hemisphere and that of the cells of the vegetal (dorsal) hemisphere adhered closely together. The blastocoel could no longer be observed. 4. The gastrulation began during the seventh cleavage. The gastrocoel was formed by a folding of the two layers of the cells. Examinations of the dissected gastrulae suggested two cooperative forces for the gastrulation: first, the epibolic or enfolding movement of the ventral ectoderm cells and secondly, the change in shape of the constituent cells. 5. The neural tube formation progressed in a similar fashion to that of vertebrates.

Animals↗

PubMed1978

Expression of a high molecular weight cell surface glycoprotein (LETS protein) by preimplantation mouse embryos and teratocarcinoma stem cells.

The expression of a high molecular weight cell surface glycoprotein (LETS, fibronectin) by preimplantation mouse embryos as well as cultured teratocarcinoma stem cells was detected by using indirect immunofluorescent staining. When each stage of preimplantation embryonic development was tested for the presence of LETS protein, none was observed on two-cell, four-cell, or eight-cell embryos, or on the morula or the outer cell layer (trophectoderm) of the early or late blastocyst. However, when the inner cell mass was isolated by immunosurgery, positive staining was observed. The intensity of the staining was significantly greater on the inner cell mass isolated from the expanded (day 4) blastocyst than on that from the early (day 3) blastocyst. Certain established cell lines of teratocarcinoma stem cells (embryonal carcinoma cells) also express cell surface LETS protein. "Nullipotent" (Nulli-SCC-1) as well as pluripotent (PSA 1) embryonal carcinoma cell lines have deposits of LETS protein concentrated in areas of cell-cell contact. In addition, a teratocarcinoma-derived endodermal cell line (PYS) was found to be capable of depositing LETS onto the substratum in a fibrillar network.Taken together, our results indicate that LETS protein is synthesized at a specific stage of preimplantation mouse embryonic development. In particular, they suggest that LETS protein is a product of the embryonic ectoderm, and that some types of embryonic endoderm are also capable of synthesizing this protein.

Animals↗

PubMed1979

Distribution patterns of DNA template activity in the embryonic tooth organ: an acridine orange ultracytochemical study.

The ultracytochemical acridine orange (AO) method has been employed to demonstrate DNA template activity within embryonic incisor tooth organs excised from New Zealand White rabbits during the 25th day of gestation. Survey ultrastructural examination revealed characteristic distribution patterns of AO positive cell populations in the inner and outer enamel epithelium and the adjacent ectomesenchyme of the cervical loop region and in populations of fibroblast-like cells connecting as a band the outer AO positive cell groups. With increasing differentiation of ameloblasts and odontoblasts the number of AO positive cells as well as the number of AO chromatin interaction products per single cell nucleus decreased. Treatment with RNase prior to incubation with AO did not result in a noticeable loss of AO chromatin interaction products suggesting that RNA is negligible as a target for AO. The present results and comparison with other biological system indicated that interaction of AO with DNA sites coding for RNA appears to be restricted to specific templates in particular physiological conditions, e.g., stimulation of cells prior to differentiation by extracellular factors.

Acridine Orange↗

PubMed1988

Trophectoderm: the first epithelium to develop in the mammalian embryo.

The first epithelium to appear during mammalian embryogenesis is the trophectoderm, a polarized transporting single cell layer that comprises the wall of the blastocyst. The trophectoderm develops concurrently with blastocoele fluid production as the morula develops into a blastocyst. The process whereby the morula becomes a fluid-filled cyst is called 'cavitation', which can be regarded as the first functional expression of the trophectoderm phenotype. The outer layer of cells of the morula comprise the nascent trophectoderm and are already morphologically polarized prior to the onset of cavitation. A major working hypothesis in the field of mammalian embryogenesis is that such polarization is a prerequisite for the initiation of cavitation. To test this hypothesis we examined morulae for their ability to cavitate during treatments that modify morphological polarity in nascent trophectoderm cells. These treatments included ouabain, different concentrations of extracellular K and Na, cytochalasins and colcemid. Ouabain and extracellular K and Na affect the activity of Na/K-ATPase, which has been implicated in the maintenance of morphological polarity of nascent trophectoderm cells. Cytochalasins and colcemid also modify apical-basal polarity of nascent trophectoderm cells and impair cavitation. The endpoints that were monitored included incidence of cavitation, rate of cavitation and the status of morphological polarity of nascent trophectoderm cells. Collectively, all of these treatments indicate that there is a functional association between an asymmetric distribution of organelles along the apical-basal axis of nascent trophectoderm cells and the ability of the embryo to produce nascent blastocoele fluid efficiently. In addition, the preimplantation embryo appears to possess two mechanisms for accumulating blastocoele fluid.

Animals↗