Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q9UIJ5 (Rec)
 58,342 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The morphology and development of junctional complexes between blastomeres of the preimplantation rabbit embryo were investigated using several approaches. Electron microscopic examination of embryos stained en bloc with uranyl acetate, and the study of junction permeability using horseradish peroxidase and lanthanum nitrate provided information on structure, intermembrane spacing and permeability of the junctional complexes. In addition, the freeze fracture technique was used with day 5 and day 6 blastocysts, since the large size of these embryos facilitated use of this method. These experiments showed that although rudimentary junctions were present between blastomeres of the early cleavage stages, effective tight junctions were not present until the blastocyst stage. Electron microscopic examination of thin sections revealed apical foci of membrane approximation or "fusion" between trophoblast cells by day 4. Freeze fracturing revealed a lattice of interconnecting ridges (on the A face) and grooves (on the B face) in the apical region between trophoblast cells of the day 5 blastocyst. This lattice formed a continuous band along the apical margin of each cell, and therefore constituted a zonula occludens. The zonula occludens of the day 5 blastocyst averages 2-3 ridges per lattice, while day 6 blastocysts had lattices that averaged 5-6 ridges. Also seen in the freeze fracture replicas from the day 5 and day 6 blastocysts were local accumulations of intramembranous particles on the A face. These particles were often observed in aggregates similar to those of previously described gap junctions. It could not be determined whether these small regions of particles were true gap junctions or a possible primitive form of gap junction because the complementary pitted surfaces (B face pits) were not demonstrated.
Anat Rec 1975 Jan
PMID:Junctional complexes in the preimplantation rabbit embryo. 4 78

Freeze-fracture replication technique was utilized to study the morphology of type II alveolar epithelial cells and alveolar contents in the late gestation of rabbit fetuses. It was shown that the lamellar inclusion bodies of type II cells were enveloped by the usual type of unit membrane with membrane-associated particles of 15 nm diameter. The interior of the inclusion bodies was composed of multiple stacks and/or whorls of membranes which were devoid of membrane-associated particles. Small vesicles within the inclusion were found more frequently with this technique than in chemically fixed thin-sectioned preparations. The intra-alveolar contents were comprised of two components; sperical bodies, which were identical to the internal contents of the lamellar bodies of type II cells, and tubular elements. These tubules most often appeared rectangular on cross-fractured faces. Triangular hexagonal fracture faces were also noted. The tubules were seen to rest on the surfaces of the spherical components. Our observations suggest that the tubular element of alveolar contents is formed through the interaction between the discharged lamellar body content and the alveolar fluid, and further suggest that at least the major constituent of type II cell lamellar bodies is lipid not bound to protein. Three new observations were made in this study; the absence of membrane-associated particles on the interior of the lamellae of the inclusions, the cross-fractured profiles of tubular elements of the alveolar contents, and the occasional multicompartmental nature of type II cell inclusions.
Anat Rec 1978 Mar
PMID:The freeze-fracture study of alveolar type II cells and alveolar content in fetal rabbit lung. 20 42

Tight junctions (zonulae occludentes) create a pericellular barrier to the diffusion of large molecules in non-keratinizing mammalian epithelia. However, in cornifying epithelia such as the epidermis, the importance of tight-junctional elements versus secreted intercellular lipid for barrier function is uncertain. In an attempt to resolve this question, we compared membrane structure in the stratum granulosum and stratum corneum of epidermis, esophagus, and vagina of newborn and adult humans and mice under both normal and various experimental conditions. We incubated pieces of epidermis in organ culture and infused tissues with lanthanum or horseradish peroxidase in vivo and in vitro. All were processed for electron microscopy of freeze-fracture replicas or thin sections. Lanthanum seeped outward to the stratum granulosum in all tissues examined--further apical migration was halted by lamellar-body contents in skin. A similar pattern of intercellular lamellar lipid deposition and membrane structure occurred in all epithelia studied. Freeze-fracture replicas of these obstructive regions revealed occasional, incomplete junctional strands (particularly in moist epithelia) and abundant lamellar material, but complete zonulae occludentes were never encountered. A possible relationship between moisture and tight junction formation was further suggested by organ culture experiments during which brief incubations stimulated an increase in the number of junctional strands and diminished numbers of lamellar bodies. We conclude that, in the epithelia studied, the deposition of secreted lamellar body contents forms the barrier to water-soluble tracer loss: tight-junctional elements are either absent or too fragmentary to constitute an effective barrier.
Anat Rec 1977 Dec
PMID:Membrane alterations during cornification of mammalian squamous epithelia: a freeze-fracture, tracer, and thin-section study. 33 80

Freeze-fracture combined with quantitative electron microscopy of the intact human erythrocyte (RBC) and ghost revealed significant differences in their intramembranous particle coefficients. External (E) fracture-faces of unfixed ghost membranes were found to contain 40% fewer particles than those of intact unfixed RBC. The particle distribution of the intact RBC membrane depended on the use of glutaraldehyde fixation and glycerol cryoprotection. Whereas glutaraldehyde- and glycerol-treated cells disclosed 70% fewer E-face particles than did intact unfixed cells, poly-L-lysine-treated, intact, unfixed RBC showed no such differences. Treatment with a combination of poly-L-lysine and glutaraldehyde, however, increased the amount of E-face particles while reducing those of the protoplasmic (P) face. The poly-L-lysine effect varied with its concentration and was unaffected by previous application of neuraminidase. Nor did the lectin phytohemagglutinin induce particle rearrangement in intact cells. Our data demonstrate that the processes of glutaraldehyde fixation and glycerol cryoprotection modify the RBC membrane by decreasing the number of E-face particles present. In addition, the combination of poly-L-lysine and glutaraldehyde alters the affinity of some particles for one half of the membrane, suggesting that in freeze-fractured RBC, chemical bonds formed at the extracellular surface of the membrane can influence particle partitioning.
Anat Rec 1977 Dec
PMID:Intramembranous particle distribution in human erythrocytes: effects of lysis, glutaraldehyde, and poly-L-lysine. 41 58

The rough endoplasmic reticulum (RER) of Xenopus laevis hepatocytes was examined by freeze-fracture and by conventional thin section electron microscopy. Much of the RER was present as stacks of cisternae at the cell periphery but, in addition, large whorls of cisternae were seen in the cytoplasm in most sections. Freeze-fracture replicas revealed fenestrae in both stacked and whorled cisternae, although the fenestrae were more numerous in the whorls. The role of these fenestrae is unknown, but such structures would facilitate access of precursors to the protein synthetic machinery in this highly metabolically active cell type. This would be particularly important in RER whorls, where the innermost cisternae would otherwise be isolated from the rest of the cytoplasm.
Anat Rec 1978 May
PMID:Fenestrae in the rough endoplasmic reticulum of Xenopus laevis hepatocytes. 64 33

Freeze-fracture of rat gastric mucosa revealed a specific set of intramembranous particles in the plasma membrane of the parietal cells. The particles were small and of square shape and formed orthogonal arrays in the P-face with corresponding orthogonal arrays of pits in the E-face. Arrays, scattered among usual globular particles, were particularly numerous at the basal pole of the cell and less concentrated on the lateral side. They were not present in the apical microvillar membrane nor in the membranes of intracellular tubulovesicles. As in other cell types in which similar arrays were described previously (e.g., astrocytes, "light" cells of the kidney collecting tubule), their presence in parietal cell membranes suggest some specialized function of these membranes not shared by plasma membranes showing only a population of globular particles. This function has yet to be identified.
Anat Rec 1978 Oct
PMID:Orthogonal arrays of particles in plasma membranes of the gastric parietal cell. 71 3

The hyaline layer (HL) is a multilayered extracellular matrix (ECM) that coats the external surfaces of sea urchin and starfish embryos. It is thought to protect and lubricate the embryo, stabilize the blastomeres during morphogenesis, and regulate nutrient intake. Ultrastructural studies of chemically fixed embryos have shown the HL to consist of two to four sublayers. However, since chemical fixatives may cause collapse and alter the positions and antigenicity of the extracellular components, fixation methods that exclude chemicals may reveal a picture of the HL closer to what is present in vivo. Freeze substitution, a fixation method whereby tissues are rapidly frozen and dehydrated at low temperatures, has proved useful for fixing material rich in ECM. In this study, embryos of the starfish Pisaster ochraceus were fixed for microscopy using freeze substitution and three chemical methods in order to determine, as accurately as possible, the structure of the HL. Embryos appear to be best preserved by freeze substitution and demonstrate a HL consisting of at least six distinct sublayers. Based on staining with anionic dyes, most sublayers appear to contain glycosaminoglycans. Freeze substituted embryos, which were also stained with monoclonal antibodies raised against their ECM, revealed that some molecules are common to all six sublayers, whereas other molecules may be restricted to specific sublayers. This suggests that each sublayer could have a different function. Additional evidence suggests that microvillus associated bodies, present in other marine invertebrate embryos, may anchor the asteroid HL to the cell surface microvilli.
Anat Rec 1991 Sep
PMID:Ultrastructural study of the hyaline layer of the starfish embryo, Pisaster ochraceus. 172 6

Pregnant rats (day 13) received 10 mg/kg of Busulfan i.p. The seminiferous tubules of their offspring from post-natal age 1 day up to day 35 were examined with TEM after fixation plus intercellular tracers, and with freeze-fracture techniques. During this period, the inter-Sertoli tight junctions of controls increase both in number and in length. Between days 10 and 13 the seminiferous cords have numerous preleptotene and leptotene spermatocytes surrounded by tracer. The inter-Sertoli junctions are tortuous and predominantly perpendicular to the basal lamina. Between ages 13 and 20 days the seminiferous epithelium reaches zygotene-pachytene stages. The tracer is stopped at the inter-Sertoli junctions at this stage, whereas it still permeates tubules displaying preleptotene and leptotene spermatocytes. Freeze-fracture shows that the orientation of inter-Sertoli junctions has changed to parallel, both to each other and to the basal lamina. In the Busulfan-treated rats, the tubules continue having, up to post-natal day 30, only Sertoli cells and scanty spermatogonia. In these, lanthanum penetration goes as far as the apical Sertoli cell region; the inter-Sertoli junctions still show tortuous strands, and most are oriented perpendicular to the basal lamina. This indicates that formation of the first competent inter-Sertoli junctions is temporo-spatially simultaneous with the appearance of zygotene-pachytene spermatocytes.
Anat Rec 1991 Jul
PMID:Correlation between blood-testis barrier development and onset of the first spermatogenic wave in normal and in busulfan-treated rats: a lanthanum and freeze-fracture study. 186 10

The morphology of spermatozoa and the initial stages of sperm-egg fusion at fertilization were investigated ultrastructurally in the rose bitterling, Rhodeus ocellatus ocellatus. Each spermatozoon is composed of a spherical head without an acrosome, two centrioles, a large mitochondrion, and a flagellum. Freeze-fracture of spermatozoa illustrates that specialized arrays of intramembranous particles (IMPs) are present on the protoplasmic facing (PF) surface of the head plasma membrane at the portion slightly in front of the centrioles. The specialized arrays, whose functions are uncertain, are parallelogram-like in shape. The distribution of the particles is random and less compact in other areas of the head plasma membrane. The number of particles on the PF surface is larger than that on the extracellular facing (EF) surface. The complementary structures of the specialized arrays are also found on a similar portion of the EF surface. An ultrastructural study clearly shows fusion of gamete plasma membranes at the initial stages of sperm entry into the egg. Membrane fusion is first observed in eggs fixed 10 seconds after insemination in fresh water. The fusion site is the microvillus membrane of a sperm entry site on the egg and the head membrane of the spermatozoon. The plasma membrane fusion of gametes is discussed relative to the distribution of the IMPs and the fusion site.
Anat Rec 1991 Feb
PMID:Initial stages of sperm-egg fusion in the freshwater teleost, Rhodeus ocellatus ocellatus. 201 6

Cell-to-cell communication within the rat anterior pituitary was investigated in 60-day-old male rats with immunohistochemistry, scanning electron microscopy, freeze-fracture electron microscopy, and conventional transmission electron microscopy. A dense cytoreticular network of cytoplasmic processes from the folliculostellate cells was found to contain immunoreactive S-100 protein and was observed throughout the anterior pituitary. Nonimmunoreactive cells, which were granular, were situated in the center of each network. Almost all of the granulated cells were situated in close proximity to the folliculostellate cells. Scanning electron microscopy revealed that the gland consisted of microlobules enclosed by a basal lamina. On the surface of the microlobules were blood vessels whose branches invaded its internal structures. Cytoplasmic processes from folliculostellate cells projected outside the microlobule. Freeze-fracture electron microscopy demonstrated the presence of numerous intramembranous particles on the P-face of the plasma membrane. Scattered on the cell surface were groups of particles forming gap junctions. Meshworks of ridges which were representations of tight junctions were also observed near clusters of microvillous fragments. Clusters of particles forming small gap junctions were located between the meshworks of tight junctions. Small gap junctions were clearly observed by conventional electron microscopy between junctional complexes in a manner similar to that seen by freeze-fracture electron microscopy. Slender cytoplasmic processes of folliculostellate cells came in contact near the basal lamina and were adjoined by small gap junctions. The ratio of nongranular cells which contained gap junctions to those in which the junctions were absent was about 1:1. The size of the gap junctions ranged from 50 nm to 3 microns. No gap junctions were observed along the plasma membranes of the granular cells. The significance of an intercellular communication system within the anterior pituitary gland of the rat is to establish a mechanism for rapid transmission of information in an organ which lacks direct innervation.
Anat Rec 1989 Aug
PMID:Intercellular communication between rat anterior pituitary cells. 278 32


1 2 3 4 Next >>