bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of gastrulation and tail formation in ascidians
Authors: Swalla Billie J. 
Published: February 2005

AbstractAscidian embryos are useful for examining how events that occur during fertilization and cleavage affect gastrulation because they gastrulate early in development, during the seventh cleavage. In ascidians, both dorsal‐ventral and anterior‐posterior axes are determined before first cleavage. The dorsal‐ventral axis is fixed along the animal‐vegetal axis of the fertilized egg following the first phase of ooplasmic segregation, perhaps due to determinants moved to the vegetal pole in concert with the myoplasm and plasma membrane components. The first ooplasmic movements appear to be driven by the actin network in the cortical myoplasm. The anterior‐posterior axis becomes apparent after the second phase of ooplasmic segregation, when the cortical myoplasm becomes detached from the egg membrane, and moves to the posterior pole of the embryo. This movement is dependent on microtubules and has been attributed to the formatior and movement of the sperm aster. A major component of the cortical myoplasm, p58, is co‐localized along the microtubules emanating from the sperm aster. Gastrulation begins during the seventh cleavage with the invagination of the large endodermal cells at the vegetal pole of the embryo. The neural plate appears as a thickening of the epidermis on the dorsal side of the larva during the ninth cleavage; then the neural folds are formed, join, and close, elaborating the neural tube. Following neurulation, the tail is elongated as the neural tube and notochord cells intercalate at the midline of the embryo. Investigations using anural (tailless) ascidian larvae suggest that some of the processes underlying elongation can be restored by the zygotic genome. Although ascidian larvae contain fewer cells and cell types than vertebrate embryos, ascidian gastrulation and morphogenesis appear to employ similar mechanisms to those in vertebrate embryos. The extent of our current knowledge about the mechanisms involved in gastrulation and tail formation is summarized, and further experiments are suggested to explore the molecular mechanisms underlying these processes. © 1993 Wiley‐Liss, Inc.
Immunohistochemistry of a human type I pneumocyte‐associated protein in lung
Authors: Singh Jagjit , Singh Gurmukh , Katyal Sikandar L. , Wong‐Chong Mari‐Lou , McCloskey Carol A. , Gottron Shirley A. 
Published: February 2005

AbstractA mouse monoclonal antibody to a human lung lavage protein was raised using proteins, with the potential ability to bind surfactant, as the immunogen. The proteins were isolated from cadaver lung lavage. The antibody was tested for its reactivity with lung and other organs. It reacted with type I pneumocytes and some of the nonciliated cells in the surface epithelium of distal bronchioles. Staining was also seen in the cells surrounding the glandular structures, superficial keratinocytes of the skin, endothelium, and nerve sheath cells. With the exception of bronchiolar cells, the stained cells have a squamous morphology, and this protein may serve as a marker or determinant of this characteristic of cells. In pathologic lungs some of the cells in air spaces with “bronchiolarization” of the epithelium exhibited staining for the protein. It could not be ascertained whether the stained cuboidal cells were reactive type II pneumocytes or distal bronchiolar cells. The intraalveolar material in pulmonary alveolar proteinosis did not show remarkable staining for the protein. Even though the protein is not unique to type I pneumocytes, it may serve as a marker for these cells in the study of their development and biology. © 1993 Wiley‐Liss, Inc.
Biosynthetic routing of pulmonary surfactant proteins in alveolar type II cells
Authors: Voorhout W. F. , Weaver T. E. , Haagsman H. P. , Geuze H. J. , Van Golde L. M. G. 
Published: February 2005

AbstractSurfactant proteins A, B, and C (SP‐A, SP‐B, and SP‐C) are synthesized in alveolar type II cells. SP‐B and SP‐C are both synthesized as large precursor molecules that are proteolytically processed to their mature sizes. In a previous immunoelectron microscopic study, we showed that precursor SP‐B is processed to its mature size in multivesicular bodies. In the present study, using a specific antibody aginst precursor SP‐C, we demonstrate that precursor SP‐C is present in the same intracellular compartments of the biosynthetic pathway, i.e., endoplasmic reticulum, Golgi complex, and multivesicular bodies, as precursor SP‐B. Since mature SP‐C is known to be present in multilamellar bodies, this suggests a biosynthetic routing and site of processing of this protein similar to those of SP‐B. Double‐labeling experiments using antibodies against SP‐A, precursor SP‐B, precursor SP‐C, and an antibody against HA I, an adaptor protein involved in the budding of transport vesicles from the Golgi complex, showed that the different surfactant proteins traverse and exit the Golgi complex via the same route. The surfactant proteins do not exit the Golgi complex via HA I‐positive coated buds or vesicles. These data are in accordance with the concept that SP‐A, SP‐B, and SP‐C are transported together through the same biosynthetic pathway via multivesicular bodies to multilamellar bodies. © 1993 Wiley‐Liss, Inc.
Aerosolized fluorescent microspheres detected in the lung using confocal scanning laser microscopy
Authors: Pinkerton Kent E. , Gallen John T. , Mercer Robert R. , Wong Viviana C. , Plopper Charles G. , Tarkington Brian K. 
Published: February 2005

AbstractAerosolized fluorescent microspheres were used to study particle deposition in site‐specific regions of the lung with confocal laser scanning microscopy. A nebulizer was used to aerosolize microspheres followed by passage through a heated discharging column to reduce static charge and to remove water surrounding each microsphere. Precoating of microspheres with albumin helped to minimize displacement during vascular fixation of the lungs. Confocal laser microscopy facilitated visualization of microspheres throughout the bronchial tree, ducts, and alveoli of the lungs. The use of fluorescent microspheres and confocal laser imaging provided distinct advantages compared with other methods to study lung particle deposition due to (1) the generation of single microspheres of uniform size by nebulization, (2) easy detection of microspheres in large slabs of microdissected lung tissues, (3) excellent resolution of tissue surfaces and microspheres for an infinite number of orientations and planes of section, and (4) the ability to visualize microspheres below fluid lining layers and on surfaces that could not easily be done by other methods of microscopy.© 1993 Wiley‐Liss, Inc.
Acute lung injury during bacterial or fungal sepsis
Authors: Lechner Andrew J. , Ryerse Jan S. , Matuschak George M. 
Published: February 2005

AbstractWe compared physiological and ultrastructural indices of acute lung injury (ALI) during septic shock caused by taxonomically diverse pathogens to distinguish ALI due to endogenous inflammatory mediators vs. microbial exotoxins or other factors. Conscious rats were infected i.v. with gram‐negativeEscherichia coli(EC, serotype 055:B5), exotoxin‐C producing gram‐positiveStaphylococcus aureus (SA), or yeast‐phaseCandida albicans(CA, a clinical isolate). Viable inocula of 1010 EC, 1010 SA, or 109 CA caused lethal shock in <24 h, but distinct types of ALI were noted after bacteria vs. fungi. Within 0.5 h of EC infection, leukocytes marginated in the lung vasculature; by death at 6–14 h, animals were hyperoxemic but not acidemic, and showed slight interstitial edema with increased wet/dry weight ratios (W/D = 5.22 ± 0.10, mean ± SE, vs. 4.86 ± 0.07 in controls, P <0.05). Similarly mild ALI occurred after 1010 SA. In contrast, within 0.5 h of CA infection, yeast were visible within lung intravascular leukocytes. By death at 6–12 h, CA animals showed hyperoxic acidemia and moderate ALI with capillary obstruction, interstitial hemorrhage, and elevated lung W/D (5.52 ± 0.13, P <0.05 vs. controls) associated with yeast‐mycelial transformation. Prior neutropenia accelerated mortality and worsened ALI after CA, with hypoxemic acidemia, increased lung W/D (7.23 ± 0.34, P <0.05 vs. other groups), capillary occlusion, perivascular and alveolar hemorrhage, and septal disruption by mycelia. Bacteremia induced large increases in serum tumor necrosis factor‐α (TNF) and interleukin‐1α within 1.5 h, but these cytokines remained low in CA animals, even at death. Neither survival nor ALI after EC or CA was altered by pentoxifylline, which attentuated TNF production, or by cyclooxygenase inhibition with ibuprofen. Thus, overall ALI severity correlated with physiological indices of pulmonary function, but ultrastructural changes correlated better with pathogen type than circulating cytokine or eicosanoid mediators. Whereas lethal bacteremia induced early cytokinemia and mild ALI with or without bacterial exotoxins, moderate ALI apparently was mediated by fungal exotoxins during lethal candidemia, which worsened during neutropenia due to enhanced mycelial proliferation.© 1993 Wiley‐Liss, Inc.
Artifacts caused by dehydration and epoxy embedding in transmission electron microscopy
Authors: Mollenhauer Hilton H. 
Published: February 2005

AbstractEpoxy resins are the principal embedding media for the preservation of tissues to be sectioned and examined by transmission electron microscopy. Their primary advantages are good ultrastructural preservation, little or no shrinkage, ease of sectioning, and reasonable stability in the electron beam. However, epoxy resins also have disadvantages; namely, some are toxic, they may mask antigenic sites to a greater extent than do some other embedding resins, and they do not penetrate tissues as well as less viscous embedding formulations. Some unusual characteristics may also be revealed, for example, as shrinkage of organelles, as problems in poststaining sections, and as movement of tissue elements within the block and section. Some of the properties of epoxy resins are discussed in this report. © 1993 Wiley‐Liss, Inc.
The granular convoluted tubule (GCT) cell of rodent submandibular glands
Authors: Gresik Edward W. 
Published: February 2005

AbstractThe granular convoluted tubule (GCT) is a segment of the duct system of all rodents, situated between the striated and intercalated ducts. It has the peculiar property of synthesizing a large variety of biologically active polypeptides whose role in saliva remains unknown. The literature on the fine structure of GCT cells is critically reviewed. Some recent developments on endocrine regulation of the structure and contents of rodent GCT cells are summarized, with emphasis on EGF, NGF, renin, and kallikrein proteases. A survey of the distribution of GCT cells in several vertebrate families is presented. © 1994 Wiley‐Liss, Inc.
Dynamics of mitochondria in living cells: Shape changes, dislocations, fusion, and fission of mitochondria
Authors: Bereiter‐Hahn J. , Vöth M. 
Published: February 2005

AbstractMitochondria are semi‐autonomous organelles which are endowed with the ability to change their shape (e.g., by elongation, shortening, branching, buckling, swelling) and their location inside a living cell. In addition they may fuse or divide. These dynamics are discussed. Dislocation of mitochondria may result from their interaction with elements of the cytoskeleton, with microtubules in particular, and from processes intrinsic to the mitochondria themselves. Morphological criteria and differences in the fate of some mitochondria argue for the presence of more than one mitochondrial population in some animal cells. Whether these reflect genetic differences remains obscure. Emphasis is laid on the methods for visualizing mitochondria in cells and following their behaviour. Fluorescence methods provide unique possibilities because of their high resolving power and because some of the mitochondria‐specific fluorochromes can be used to reveal the membrane potential. Fusion and fission often occur in short time intervals within the same group of mitochondria. At sites of fusion of two mitochondria material of the inner membrane, the matrix compartment seems to accumulate. The original arrangement of the fusion partners is maintained for some minutes. Fission is a dynamic event which, like fusion, in most cases observed in vertebrate cell cultures is not a straightforward process but rather requires several “trials” until the division finally occurs. Regarding fusion and fission hitherto unpublished phase contrast micrographs, and electron micrographs have been included. © 1994 Wiley‐Liss, Inc.
Interactions between brain mitochondria and cytoskeleton: Evidence for specialized outer membrane domains involved in the association of cytoskeleton‐associated proteins to mitochondria in situ and in vitro
Authors: Leterrier J. F. , Rusakov D. A. , Nelson B. D. , Linden M. 
Published: February 2005

AbstractThe surface distribution of several proteins (porin, hexokinase, and two proteins associated with microtubules or actin filaments) on the outer membrane of brain mitochondria was analyzed by immunogold labelling of purified mitochondria in vitro. The results suggest the existence of specialized domains for the distribution of porin in the outer mitochondrial membrane. Similarities between the distribution of porin and the distribution of microtubule‐associated proteins bound in vitro to mitochondria suggested that mitochondria and microtubules interact by binding microtubule‐associated proteins to porin‐containing domains of the outer membrane. This hypothesis was supported by biochemical studies on outer mitochondrial proteins involved in in vitro binding of cytoskeleton elements. In vitro interactions between mitochondria and microtubules or neurofilaments were analyzed by electron microscopy. These studies revealed cross‐bridging between the outer membrane of mitochondria and the two cytoskeleton elements. Cross‐bridging was influenced by ATP hydrolysis and by several proteins associated with the surface of mitochondria or with microtubules. In addition, unidentified proteins which were recognized by antibodies to all intermediate filaments subunits were associated either with the mitochondrial surface or with microtubules. This data suggest the participation of additional cytoplasmic proteins in the interactions between cytoskeleton elements and mitochondria. © 1994 Wiley‐Liss, Inc.
Specimen preparation of free‐standing, thick‐metal, multilayered films in cross section
Authors: Wall Mark A. 
Published: February 2005

AbstractA new preparation method permits the production of large‐area, electron‐transparent, transmission electron microscopy (TEM) specimens in cross section of free‐standing, thick, multilayered structures. Such production often has been difficult in the past because of large chemical differences between the component layers in the multilayer. This difference usually results in a large difference in thinning rates between the layers. A unique combination of electroplating, lapping, dimpling, and low‐angle ion milling is a successful and reproducible technique for producing high‐quality TEM specimens of these complex materials. Procedures and results presented here are for a 304 stainless‐steel/copper multilayer having a repeat period of 20 nm and a total thickness of 20 μm. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
A morphological view on mitochondrial protein targeting
Authors: van der Klei Ida J. , Veenhuis Marten , Neupert Walter 
Published: February 2005

AbstractMitochondrial protein targeting includes both intramitochondrial sorting of proteins encoded by the organellar genome and import and subsequent sorting of nuclear encoded precursor proteins. Only a few proteins are encoded by the mitochondrial genome and synthesized in the organellar matrix. These include predominantly inner membrane proteins that are perhaps co‐translationally inserted into this membrane. Biochemical data suggest that insertion into the inner membrane may be confined to the inner boundary membrane. Ultrastructurally, however, a preferential association of ribosomes with either inner boundary or cristae membranes has not been established.The majority of the mitochondrial proteins are nuclear encoded and synthesized as precursors in the cytosol. Electron microscopic studies revealed that import of precursor proteins is generally confined to sites where both mitochondrial envelope membranes are closely apposed. In line with these observations, biochemical studies indicated that precursor proteins destined for the inner membrane or matrix have to interact with the energized inner membrane to allow complete passage of the precursor through the outer membrane. As a consequence, the mitochondrial envelope membranes have to be in close proximity at protein import sites.In isolated mitochondria distinct sites (designated as contact sites) exist where both envelope membranes are closely apposed and presumably stably associated. In situ, however, mitochondrial boundary membranes are in close proximity over large areas that cover almost the entire mitochondrial periphery. Consequently, the relative area of the mitochondrial surface, where both boundary membranes are in sufficient proximity for allowing protein translocation, is generally larger in situ compared to that in isolated organelles.Immunocytochemical localization studies showed a rather random distribution of components of the mitochondrial protein translocation machinery over the entire mitochondrial surface and not confined to contact sites.Based on these ultrastructral data and recent biochemical findings we propose that mitochondrial protein import sites are dynamic in nature and include relatively labile regions of close association of the boundary membranes. In vitro, however, mitochondrial protein import may preferentially take place at or near the presumably stable contact sites. © 1994 Wiley‐Liss, Inc.
Electron microscopic studies of magnetosomes in magnetotactic bacteria
Authors: Bazylinski Dennis A. , Garratt‐Reed Anthony J. , Frankel Richard B. 
Published: February 2005

AbstractElectron microscopic studies on magnetosomes in magnetotactic bacteria have revealed much information on their composition, structure, and even the formation of their mineral phase. The mineral phases of the magnetosomes are of two general types: iron oxides and iron sulfides. Iron oxide‐type magnetosomes contain particles of the ferrimagnetic mineral magnetite (Fe3O4) while the iron sulfide‐type contain ferrimagnetic greigite (Fe3S4), greigite and non‐magnetic pyrite (FeS2), or possibly ferrimagnetic pyrrhotite (Fe7S8). Regardless of their composition, the crystalline particles in magnetosomes have a narrow size range: approximately 35 to 120 nm. Magnetite crystals in this size range are single‐magnetic‐domains and confer a permanent magnetic dipole moment to the cell. The single‐domain size range for greigite is not known but is probably similar to that for magnetite.The morphology of the particles in the bacterial magnetosomes appears to be species‐specific. Morphologies of magnetite crystals in different species of magnetotactic bacteria include cubooctahedra, parallelepipedal (truncated hexahedral or octahedral prisms), and tooth‐ or bullet‐shaped (anisotropic). Morphologies of greigite particles include cubo‐octahedra and rectangular prismatic. The greigite‐pyrite particles are generally pleomorphic with no consistent crystalline morphology. A membrane has been shown to surround the particles in some organisms and may be involved in the formation of the crystalline phase while also providing physical constraints on the size and the shape of the crystal. These results clearly indicate that the biomineralization process involved in the bacterial magnetosome, a good example of a self‐assembled structure on a nanometer scale, is highly controlled by the organism. © 1994 Wiley‐Liss, Inc.
Structure of butterfly scales: Patterning in an insect cuticle
Authors: Ghiradella Helen 
Published: February 2005

AbstractAll butterfly and moth scales and bristles are made of non‐living insect cuticle. Each is the product of a single epithelial cell, and all share the same basic architecture. However, some are highly specialized, and their cuticle is further elaborated into stacks of thin‐films, lattices, or other minute structures, many of which first came to our attention because they interact, with light to produce structural colors. The scale cell forms the scale by extruding a projection of itself and secreting around it the outer epicuticle, a thin cuticular envelope which will form the outermost layer of the scale. The inner layers of cuticle, collectively called the procuticle, are secreted thereafter and go on to form the lattices, pillars, or other internal structures of the scale. We believe that the pattern‐forming mechanisms used by the cell to shape the cuticle into its finished form include elastic buckling of the outer epicuticle to produce external folds, and “masking” of certain areas of the original epicuticular envelope to produce thin spots which will break through to become windows. Varied though they be, all insect cuticular patterns have common basic elements, which suggests that our findings may be generalized to other highly patterned insect cuticles, particularly those formed by single cells. © 1994 Wiley‐Liss, Inc.
Cryo‐electron microscopy of deoxy‐sickle hemoglobin fibers
Authors: Lewis Michael R. , Gross Leon J. , Josephs Robert 
Published: February 2005

AbstractDeoxy‐sickle hemoglobin (HbS) polymerizes in vivo into long helical fibers which fill the red cell and make it rigid. This impedes red cell passage through the capillaries and is responsible for the clinical manifestations of sickle cell disease. Images of individual and laterally associated HbS fibers were obtained by electron microscopy of frozen hydrated specimens. Each fiber possesses variable pitch, having from 6° to 12° rotation per unit cell. Laterally associated HbS fibers display systematic inter‐fiber contacts in spite of their pitch variations, and exhibit better order than isolated fibers. This suggest that inter‐fiber contacts can act to couple fibers mechanically and might therefore be a factor in rigidifying red cells in vivo. Fiber variability was attributed to local torsional variations with a standard deviation of 2.5°, but which are weakly coupled over a length of 2.25 unit cells. Variable pitch produces structural changes of as large as 5 Å azimuthally and 6 Å axially in HbS fiber unit cells. © 1994 Wiley‐Liss, Inc.