Electron microscopic studies of the morphology of the corneal stroma in the rabbit cornea using the freeze-fracture technique

1982 ◽  
Vol 218 (4) ◽  
pp. 221-224 ◽  
Author(s):  
H. -J. Sieweke ◽  
H. Robenek ◽  
H. Themann
Keyword(s):  
Freeze Fracture ◽  
Corneal Stroma ◽  
Electron Microscopic ◽  
Rabbit Cornea ◽  
Microscopic Studies

Determinants of biliary secretion in isolated perfused skate liver

1982 ◽  
Vol 242 (4) ◽  
pp. G319-G325 ◽  
Author(s):  
J. S. Reed ◽  
N. D. Smith ◽  
J. L. Boyer
Keyword(s):  
Tight Junctions ◽  
Bile Flow ◽  
Perfusion Pressure ◽  
Freeze Fracture ◽  
Biliary Tree ◽  
Solute Diffusion ◽  
Electron Microscopic ◽  
Bile Formation ◽  
Ionic Lanthanum ◽  
Microscopic Studies

In the isolated perfused liver of the little skate, Raja erinacea, bile flow averaged 5.07 +/- 0.58 (mean +/- SE) microliters.h-1.g liver-1 in 21 experiments at a perfusion pressure of 5.0 cm Ringer compared to 3.79 +/- 0.32 in 38 experiments at 2.5 cm (P less than 0.05). [14C]inulin readily entered skate bile. Bile-to-plasma [14C]inulin ratios corrected for delay in transit time, averaged 0.46 +/- 0.07 at 1 h and rose to 0.74 +/- 0.06 by 4 h, although bile flow remained constant. In experiments in which [14C]inulin reached equilibrium between bile and plasma, the bile-to-plasma ratio conformed to the theoretical relationship between bile flow, solvent drag, and inert solute diffusion predicted at extremely low bile flows, but demonstrated that the skate biliary tree is more permeable to inulin than that of the rat. Electron microscopic studies demonstrated that ionic lanthanum could traverse the tight junctions. However, freeze-fracture studies of junction structure did not differ qualitatively from similar studies in the rat. Partial dependence of bile flow on perfusion pressure, high bile-to-plasma inulin ratios, and permeability of the canalicular tight junctions to ionic lanthanum all suggest that the paracellular pathway may be an important component of bile formation in the skate.

Light and Electron Microscopic Studies Regarding Cell Contractility and Cell Coupling in Light Sensitive Smooth Muscle Cells from the Isolated Frog Iris Sphincter

1987 ◽  
Vol 42 (7-8) ◽  
pp. 977-985 ◽  
Author(s):  
Klaus V. Wolf
Keyword(s):  
Gap Junctions ◽  
Freeze Fracture ◽  
Muscle Cells ◽  
Sphincter Muscle ◽  
Cell Coupling ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Cell Contractility ◽  
Microscopic Studies ◽  
Iris Sphincter

(1) In light microscopical studies of living isolated frog irises, it was found that the maximal areas of experimentally light induced contractions in the m. sphincter pupillae were located beneath small illuminated regions. There were no visible contractions of muscle cells outside the illuminated areas. It was shown that exposure to light could directly cause contractions of isolated single sphincter muscle cells. (2) Junctional structures of the iris sphincter cells were studied by means of thin sections and freeze fracture electron microscopy. Intermediate junctions, a few focal tight junctions and occasional small gap junctions were identified. Pit containing intramembranous particles which resemble gap junction connexons were found in large numbers, dispersed over the plasmalemmas of sphincter muscle cells. From these physiological and morphological observations, it is concluded that sphincter muscle cells of the frog iris may be coupled via gap junctions, but that the cell coupling is not sufficiently extensive to form the basis for a functional syncytium.

Transmission and Scanning Electron Microscopic studies of ocular leprosy in nine-banded armadillos

1989 ◽  
Vol 47 ◽  
pp. 1038-1039
Author(s):  
R. Malaty ◽  
L. Pedroza ◽  
R.W. Beuerman
Keyword(s):  
Light And Electron Microscopy ◽  
Corneal Stroma ◽  
Mycobacterium Leprae ◽  
Lepromatous Leprosy ◽  
Electron Microscopic ◽  
Ocular Complications ◽  
Scanning Electron Microscopic ◽  
Microscopic Studies ◽  
Histopathological Studies ◽  
Preventable Blindness

Leprosy is one of the leading causes of preventable blindness in the world, yet It is largely ignored in blindness prevention programs. To date, little is known about the pathogenesis of ocular leprosy in humans. Histopathological studies have been necessarily 1imited to eyes removed at autopsy or enucleated from patients with advanced lepromatous leprosy. In an attempt to define the pathogenesis of the ocular complications of leprosy, we have studied the eyes of animal models namely, nine-banded armadillos with 1epromatous leprosy and injected Mycobacterium leprae (M. leprae) directly in the corneal stroma of armadillos.Fifty armadillos with experimental or naturally-acquired lepromatous leprosy were studied. Six armadillos were injected in the corneal stroma with 1 ul of an M. leprae suspension and examined two and four months later. Both eyes of each animal were enucleated at autopsy, fixed in paraformaldehyde-glutaraldehyde and processed for light and electron microscopy (EM). For light microscopy, the eyes were embedded in plastic methacrylate and sections stained with a modified acid-fast stain. For EM, tissues were post fixed in 1% OsO4 dehydrated, and embedded in epon.

Rapid bulk replacement of acceptor membrane by donor membrane during phagosome to phagoacidosome transformation in Paramecium

1995 ◽  
Vol 108 (3) ◽  
pp. 1263-1274 ◽  
Author(s):  
R.D. Allen ◽  
N.P. Bala ◽  
R.F. Ali ◽  
D.M. Nishida ◽  
M.S. Aihara ◽  
...  
Keyword(s):  
Active Drug ◽  
Freeze Fracture ◽  
Vesicle Membrane ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Replacement Process ◽  
Rapid Changes ◽  
Transmission Electron Microscopic ◽  
Microscopic Studies ◽  
The Times

The extent to which a donor membrane will be retrieved, or if it is retrieved at all after it fuses with an acceptor membrane, is usually difficult to determine. We have studied the dynamics of membrane retrieval in the phagosome system of Paramecium multimicronucleatum using six monoclonal antibody markers. Our previous freeze-fracture and transmission electron microscopic studies have indicated that extensive changes take place in the membrane of the young phagosome as it progresses through its cycle. Using immunofluorescence and immunoelectron microscopy to determine the times of entry and exit of these individual antigens into the digestive vacuole system, we showed that two hydrophilic antigens, one located on the cytosolic and one on the lumenal side of the discoidal membrane (phagosome membrane precursor), were completely retrieved from the phagosome by tubulation within the first three minutes. At the same time that this membrane was retrieved, membrane from a second population of vesicles, the acidosomes, fused with the phagosome to produce the phagoacidosome. On the basis of immunogold localization on cryosections of a total of six antigens, the two specific for phagosome/discoidal vesicle membrane as well as four specific for the acidosome/phagoacidosome membrane, this replacement is total. We also showed that in the presence of the actin-active drug cytochalasin B, this replacement was essentially prevented. However, when vacuole acidification was neutralized by ammonium chloride, this replacement process continued unaffected after a lag. Consequently, acidification, per se, is not required to trigger the replacement of the phagosome membrane. We conclude, on the basis of these studies as well as our previous freeze-fracture studies that during phagoacidosome formation most of the acceptor membrane is retrieved and is replaced by the donor membrane. This shows that at least one cell type possesses the mechanisms needed to substantially replace the membrane of a phagosomal compartment when radical and rapid changes are needed to modulate the digestive and absorptive processes.

Electron microscopic studies on ultrathin frozen sections of lactating mouse mammary gland

1978 ◽  
Vol 36 (2) ◽  
pp. 46-47
Author(s):  
Jan Zarzycki ◽  
Joseph Szroeder
Keyword(s):  
Mammary Gland ◽  
Protein Denaturation ◽  
Chemical Constituents ◽  
Freeze Substitution ◽  
Electron Microscopic Examination ◽  
Mouse Mammary Gland ◽  
Electron Microscopic ◽  
Preparation Methods ◽  
Microscopic Studies ◽  
Ultrathin Frozen Sections

The mammary gland ultrastructure in various functional states is the object of our investigations. The material prepared for electron microscopic examination by the conventional chemical methods has several limitations, the most important are the protein denaturation processes and the loss of large amounts of chemical constituents from the cells. In relevance to this,one can't be sure about a degree the observed images are adequate to the realy ultrastructure of a living cell. To avoid the disadvantages of the chemical preparation methods,some autors worked out alternative physical methods based on tissue freezing / freeze-drying, freeze-substitution, freeze-eatching techniqs/; actually the technique of cryoultraraicrotomy,i,e.cutting ultrathin sections from deep frozen specimens is assented as a complete alternative method. According to the limitations of the routine plastic embbeding methods we were interested to analize the mammary gland ultrastructure during lactation by the cryoultramicrotomy method.

Freeze-Fracture Replication in the Ultrastructure of Blue-Green Algae

1967 ◽  
Vol 25 ◽  
pp. 74-75
Author(s):  
L. V. Leak
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Green Algae ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Electron Microscopic ◽  
Photosynthetic Membranes ◽  
Blue Green Algae ◽  
Cell Biol ◽  
Cellular Components

Electron microscopic observations of freeze-fracture replicas of Anabaena cells obtained by the procedures described by Bullivant and Ames (J. Cell Biol., 1966) indicate that the frozen cells are fractured in many different planes. This fracturing or cleaving along various planes allows one to gain a three dimensional relation of the cellular components as a result of such a manipulation. When replicas that are obtained by the freeze-fracture method are observed in the electron microscope, cross fractures of the cell wall and membranes that comprise the photosynthetic lamellae are apparent as demonstrated in Figures 1 & 2.A large portion of the Anabaena cell is composed of undulating layers of cytoplasm that are bounded by unit membranes that comprise the photosynthetic membranes. The adjoining layers of cytoplasm are closely apposed to each other to form the photosynthetic lamellae. Occassionally the adjacent layers of cytoplasm are separated by an interspace that may vary in widths of up to several 100 mu to form intralamellar vesicles.

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