Melanogenesis in amphibians

Development ◽  
1970 ◽  
Vol 24 (2) ◽  
pp. 447-454
Author(s):  
John J. Eppig
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Notophthalmus Viridescens ◽  
Retinal Pigmented Epithelium ◽  
Pigmented Epithelium ◽  
In Cells

Electron microscopy of 11-day-old Notophthalmus viridescens retinal pigmented epithelium reveals particulate premelanosomes which are identical to the melanosomes found in the oocyte. These organelles, when found in the pigmented epithelium, are called premelanosomes because they undergo further maturation to form relatively homogeneous, spherical melanosomes. At this stage, oocyte melanosomes found in cells other than melanocytes have not undergone this subsequent maturation. Elongated melanosomes which develop from fibrillar premelanosomes are also found in the pigmented epithelial cells. Treatment with phenylthiourea blocks the maturation of both the fibrillar and particulate premelanosomes.

Adenomatoid Tumor of the Testis, A Mesonephric Hamartoma

1971 ◽  
Vol 29 ◽  
pp. 318-319
Author(s):  
Raoul Fresco ◽  
Mary Chang-Lo
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Fibrous Tissue ◽  
Salient Feature ◽  
Luminal Surface ◽  
Adenomatoid Tumor ◽  
Ultrastructural Studies ◽  
Epithelial Origin ◽  
Brush Borders ◽  
Cell Processes

Confusion surrounds the nature of the “adenomatoid tumor” of the testis, as evidenced by the large number of synonyms which have been ascribed to it. Various authors have considered the tumor to be of endothelial, mesothelial or epithelial origin. There appears to be no controversy as to the stromal elements of the tumor, which consists mainly of smooth muscle and fibrous tissue. It is the irregular gland-like spaces which have given rise to the numerous theories as to its histogenesis, and even recent ultrastructural studies fail to agree on the origin of these structures.Electron microscopy of a typical intrascrotal adenomatoid tumor showed the gland-like spaces to be lined by epithelial cells (Fig. 1), rich in cytoplasmic tonofibrils and united to each other by numerous desmosomes (Fig. 2). The most salient feature of these epithelial cells was the presence on their luminal surface of numerous long and repeatedly branching microvillous structures of the type known as stereocilia (Fig. 3). These are extremely long slender cell processes which are as much as three to four times the length of those in brush borders.

Three-dimensional organization and functional relationships of endocytotic compartments in pig intestinal epithelial cells

1992 ◽  
Vol 50 (1) ◽  
pp. 576-577
Author(s):  
Julian P. Heath ◽  
Buford L. Nichols ◽  
László G. Kömüves
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Intestinal Epithelial Cells ◽  
Three Dimensional ◽  
Intestinal Epithelial ◽  
Cell Surfaces ◽  
Basal Surface ◽  
Functional Relationships

The newborn pig intestine is adapted for the rapid and efficient absorption of nutrients from colostrum. In enterocytes, colostral proteins are taken up into an apical endocytotic complex of channels that transports them to target organelles or to the basal surface for release into the circulation. The apical endocytotic complex of tubules and vesicles clearly is a major intersection in the routes taken by vesicles trafficking to and from the Golgi, lysosomes, and the apical and basolateral cell surfaces.Jejunal tissues were taken from piglets suckled for up to 6 hours and prepared for electron microscopy and immunocytochemistry as previously described.

Revisiting staining of biological samples for electron microscopy: perspectives for recent research

2021 ◽  
Author(s):  
Maren T. Kuchenbrod ◽  
Ulrich S. Schubert ◽  
Rainer Heintzmann ◽  
Stephanie Hoeppener
Keyword(s):  
Electron Microscopy ◽  
Biological Samples ◽  
Active Sites ◽  
In Cells

This review revisits staining protocols for electron microscopy focussing on the visualization of active sites, i.e. enzymes, metabolites or proteins, in cells and tissues, which were never established as standard protocols in electron microscopy.

scholarly journals EFFECTS OF CYCLIC AMP AND SEPHADEX FRACTIONS OF CHICK EMBRYO EXTRACT ON CLONED RETINAL PIGMENTED EPITHELIUM IN TISSUE CULTURE

1974 ◽  
Vol 61 (2) ◽  
pp. 369-382 ◽  
Author(s):  
D. A. Newsome ◽  
R. T. Fletcher ◽  
W. G. Robison ◽  
K. R. Kenyon ◽  
G. J. Chader
Keyword(s):  
Molecular Weight ◽  
Chick Embryo ◽  
Adenosine Monophosphate ◽  
Cell Number ◽  
Retinal Pigmented Epithelium ◽  
Culture Dish ◽  
Adhesive Properties ◽  
Embryo Extract ◽  
Chick Embryo Extract ◽  
Pigmented Epithelium

The effects of dibutyryl cyclic 3',5'-adenosine monophosphate (BcAMP) and Sephadex G-25 fractions of chick embryo extract on the growth rate, morphology, and pigmentation of normal chick retinal pigmented epithelium (PE) were investigated. Seven cloned PE cell lines were each grown in modified Ham's F-12 medium alone (F-12), or in F-12 supplemented with either high molecular weight (H) or low molecular weight (L) fractions of chick embryo extract. Cells grown in F-12 alone or in L medium formed compact epithelial sheets, whereas cells grown in H had a fibrocytic appearance and formed poorly organized monolayers. In H plus BcAMP, cell morphology was more epithelioid than in H alone, and generally the monolayers appeared more differentiated. Under each of these three culture conditions, 2 x 10-4 M BCAMP retarded the increase in cell number and decreased the final number of cells per culture dish, but had little effect on plating efficiency. BcAMP also increased the rate of cell adhesion to a plastic substratum. Pigmentation was marked in cultures grown in F-12 or in L alone, but the addition of BcAMP dramatically reduced visible pigmentation. This effect was reversed when BcAMP was removed from the culture medium. Thus BcAMP modifies cell and colonial morphology, rate of cell accumulation, adhesive properties, and pigmentation of normal PE cells.

scholarly journals Effects of the cationic protein poly-L-arginine on airway epithelial cellsin vitro

2002 ◽  
Vol 11 (3) ◽  
pp. 141-148 ◽  
Author(s):  
Shahida Shahana ◽  
Caroline Kampf ◽  
Godfried M. Roomans
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Cell Damage ◽  
Membrane Damage ◽  
Light And Electron Microscopy ◽  
Airway Epithelial Cells ◽  
Airway Epithelial ◽  
Cationic Protein ◽  
Induced Apoptosis

Background: Allergic asthma is associated with an increased number of eosinophils in the airway wall. Eosinophils secrete cationic proteins, particularly major basic protein (MBP).Aim: To investigate the effect of synthetic cationic polypeptides such as poly-L-arginine, which can mimic the effect of MBP, on airway epithelial cells.Methods: Cultured airway epithelial cells were exposed to poly-L-arginine, and effects were determined by light and electron microscopy.Results: Poly-L-arginine induced apoptosis and necrosis. Transmission electron microscopy showed mitochondrial damage and changes in the nucleus. The tight junctions were damaged, as evidenced by penetration of lanthanum. Scanning electron microscopy showed a damaged cell membrane with many pores. Microanalysis showed a significant decrease in the cellular content of magnesium, phosphorus, sodium, potassium and chlorine, and an increase in calcium. Plakoglobin immunoreactivity in the cell membrane was decreased, indicating a decrease in the number of desmosomes.Conclusions: The results point to poly-L-arginine induced membrane damage, resulting in increased permeability, loss of cell-cell contacts and generalized cell damage.

Scanning electron microscopy of the operculum of Garra lamta (Hamilton) (Cyprinidae:Cypriniformes), an Indian hill stream fish

2010 ◽  
Vol 58 (3) ◽  
pp. 182 ◽  
Author(s):  
Swati Mittal ◽  
Usha Kumari ◽  
Pinky Tripathi ◽  
Ajay Kumar Mittal
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Epithelial Cells ◽  
Goblet Cells ◽  
Stream Fish ◽  
Male And Female ◽  
Fish Breeding ◽  
Inner Surface ◽  
Garra Lamta ◽  
Scanning Electron

The surface architecture of the epidermis on the outer surface of the operculum (OE) and the epithelium on the inner surface of the operculum (EISO) of Garra lamta was examined by scanning electron microscopy. The surface appeared smooth on the OE and wavy on the EISO. A wavy epithelium is considered to facilitate an increase in its stretchability, during the expansion of the branchial chamber. The OE and the EISO were covered by a mosaic pavement of epithelial cells with characteristic patterns of microridges and microbridges. Interspersed between the epithelial cells were mucous goblet cell pores, which were not significantly different in number in the OE and the EISO. Nevertheless, their surface area in the EISO was significantly higher than in the OE. This could be an adaptation to secrete higher amounts of mucus on the EISO for keeping the branchial chamber lining clean, avoiding clogging, the increased slipperiness reducing friction from water flow and increased efficiency in protecting against microbial attachments. Rounded bulges on the OE and the EISO were associated with mucous goblet cells. The absence of the taste buds in the EISO, in contrast to the OE, suggests that their function in the branchial chamber may not be of much significance in this fish. Breeding tubercles on the OE are believed to facilitate better contact between the male and female during breeding.

scholarly journals Five Recombinant Simian Immunodeficiency Virus Pseudotypes Lead to Exclusive Transduction of Retinal Pigmented Epithelium in Rat

2002 ◽  
Vol 6 (4) ◽  
pp. 446-454 ◽  
Author(s):  
Ghislaine Duisit ◽  
Hervé Conrath ◽  
Sylvie Saleun ◽  
Sebastien Folliot ◽  
Nathalie Provost ◽  
...  
Keyword(s):  
Simian Immunodeficiency Virus ◽  
Retinal Pigmented Epithelium ◽  
Immunodeficiency Virus ◽  
Pigmented Epithelium

Oxidation of glucose carbon entering the TCA cycle is reduced by glutamine in small intestine epithelial cells

1995 ◽  
Vol 268 (6) ◽  
pp. G879-G888 ◽  
Author(s):  
C. E. Kight ◽  
S. E. Fleming
Keyword(s):  
Small Intestine ◽  
Epithelial Cells ◽  
Glucose Oxidation ◽  
Tca Cycle ◽  
Proximal Segment ◽  
Distal Small Intestine ◽  
Glucose Carbon ◽  
The Tca Cycle ◽  
Oxidation Of Glucose ◽  
In Cells

The influence of glutamine on glucose oxidation was assessed in epithelial cells isolated from the mucosa of the proximal, mid-, and distal small intestine of young, fed, male rats. Glucose oxidation declined along the length of the small intestine, with values from the mid- and distal segments representing approximately 55% and 40%, respectively, of the value from the proximal segment. A gradient along the small intestine was noted also in the influence of glutamine on glucose oxidation: glutamine suppressed glucose oxidation approximately 60% in the proximal small intestine, 39% in the mid-intestine, and 31% in the distal small intestine. Glutamine suppressed the oxidation of glucose carbon that entered the tricarboxylic acid (TCA) cycle; this was determined using CO2 ratios derived from acetate and glucose isotopes. In cells from the proximal segment, the probability that carbon entering the cycle would complete one full turn was reduced by glutamine from 0.77 to 0.28. The entry of glucose-derived pyruvate into the TCA cycle did not appear to be influenced by the presence of glutamine, however. Glutamine had no influence on the proportion of glucose metabolism that occurred via the pentose phosphate pathway (which averaged 5% or less), but reduced flux of carbon through pyruvate carboxylase relative to flux through pyruvate dehydrogenase from 40% to 9% in cells from the proximal segment. These data suggest that, in the presence of glutamine, the fate of pyruvate carbon (derived from glucose or elsewhere) entering the TCA cycle is altered from that of oxidation to anaplerosis and subsequent efflux of TCA cycle intermediates into newly synthesized compounds.

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