bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasticity of cell organization during differentiation of normal and oncogene transformed granulosa cells
Authors: Amsterdam A. , Aharoni D. 
Published: February 2005

AbstractGranulosa cells, which nurse the oocyte and serve as a major source for estradiol and progesterone production, undergo major morphological changes which correlate very well with modulation of their steroidogenic capacity. These include changes in intercellular contacts and communication, in cell membrane receptors, and in the development and organization of organelles associated with steroidogenesis (i.e., mitochondria, smooth endoplasmic reticulum, lipid droplets, and lysosomes). These biochemical and morphological changes can also be obtained in primary cultures as well as in oncogene transformed granulosa cell lines established recently in our laboratory. A growing body of evidence suggests that plasticity of the cytoskeleton plays a major role in the biochemical and morphological differentiation of granulosa cells as well as in other steroidogenic cells. © 1994 Wiley‐Liss, Inc.
Molecular and cellular mechanisms of mitochondrial nuclear division and mitochondriokinesis
Authors: Kuroiwa Tsuneyoshi , Ohta Toshiro , Kuroiwa Haruko , Shigeyuki Kawano 
Published: February 2005

AbstractOur present understanding of mitochondrial division can be summarized as follows:Mitochondria contain a specific genome, synthesize their own DNA, and multiply semi‐autonomously. Strands of mitochondrial DNA (mt‐DNA) in the in vivo organelles of all eukaryotes are organized to form mitochondrial nuclei (nucleoids) (mt‐nuclei) with specific proteins including a histone‐like protein and transcription factors at the central region of the mitochondrion. We can easily observe the mt‐nucleus in vivo mitochondria in various organisms such as fungi, algae, plants, and animals by using high‐resolution epifluorescence microscopy. Therefore, the process of mitochondrial division can be clearly separated into two main events: division of the mt‐nuclei and mitochondriokinesis analogous to cytokinesis.Mitochondria undergo binary division which is accompained by the division of the mt‐nucleus. A remarkable characteristic of mitochondrial multiplication during the mitochondrial life cycle is that mitochondria can multiply the mt‐chromosome by endoduplication until 50–100 copies are present. Mitochondria can then divide without mitochondrial DNA synthesis to eventually contain 1–5 copies of the mt‐chromosome. This characteristic phenomenon can be observed during cell differentiation, such as during the formation of plasmodia and sclerotia of Physarum polycephalum and during embryogenesis and the formation of meristematic tissues in plants.The mitochondrial chromosome has a mitochondrial “kinetochore (centromere)” which is A‐T rich and contains specific sequences such as topoisomerase binding sites, tandem repeats, and inverted repeats. A bridge of proteins may exist between the kinetochore DNA and membrane systems. Mitochondrial chromosomes can divide according to the growth of a membrane system between the kinetochores.Mitochondriokinesis progresses steadily along with mitochondrial nuclear division. As the membrane at the equatorial region of a mitochondrion contracts, the neck of the cleavage furrow narrows, and eventually the daughter mitochondria are separated. An actin‐like protein may power mitochondriokinesis by separating the daughter mitochondria. In general, mitochondriokinesis occurs by contraction rather than by partition of the inner membrane. © 1994 Wiley‐Liss, Inc.
Cytochrome c oxidase: Structural studies by electron microscopy of two‐dimensional crystals
Authors: Frey Terrence G. 
Published: February 2005

AbstractCytochrome c oxidase is a complex integral membrane protein consisting of 13 different polypeptide chains and four metal centers having a total molecular weight of approximately 200,000 daltons. It can be isolated in two 2‐dimensional crystalline forms differing in aggregation state of the enzyme. One crystal form consists of cytochrome oxidase dimers (approximately 400,000 daltons) embedded unidirectionally in the lipid bilayer of a collapsed vesicle while the other form consists of crystalline sheets of cytochrome oxidase monomers. Both crystal forms have been studied by electron microscopy during the past two decades, and this paper summarizes the results of early structural studies as well as more recent results applying techniques of cryelectron microscopy and digital image processing. The structure of frozen‐hydrated cytochrome oxidase dimers at 20 Å resolution is discussed as well as the packing of monomers within dimers and the site of cytochrome c binding. © 1994 Wiley‐Liss, Inc.
Biomineralization: New directions in crystal science
Authors: Heywood Brigid R. 
Published: February 2005

AbstractEffective protocols for controlling crystal structure, size, and morphology attract considerable interest given the requirement for particles of modal size and shape in many areas of materials fabrication and the importance of crystallochemical selectivity in determining the exploitable properties of inorganic solids. For this reason biomineralization merits particular attention since many biominerals are deposited in a highly controlled manner to produce crystals which are uniformly sized and crystallographically unique. Studies of biominerals have revealed that while a complex array of strategies have evolved for regulating their formation, one feature is common to the biological paradigm; interactions between organized biopolymeric assemblies and the nascent inorganic solids play a pivotal role in controlling the crystallization process. In order to gain a better understanding of the molecular interactions which take place at organic‐inorganic interface and address the fundamental chemical problems of biomineralization, a crystal chemical approach has been adopted. Organized organic assemblies (phospholipid vesicles, Langmuir monolayers, polypetide templates) of precise molecular design (head group identity, packing conformation, peptide sequence, etc.) were assayed for their effectiveness in controlling the nucleation and growth of inorganic solids. This work has established that through systematic changes in the nature of the organic matrix the size, crystallographic orientation, and growth of the mineral phase can be controlled. Critical to this process was the translation of specific molecular information at the organic‐inorganic interface: epitaxial alignment, stereochemical complementarity, and electrostatic interactions were an essential feature of this recognition event. © 1994 Wiley‐Liss, Inc.
Electron and atomic force microscopic investigations of lead selenide crystals grown under monolayers
Authors: Yang J. , Fendler J. H. , Jao T.‐C. , Laurion T. 
Published: February 2005

AbstractLead selenide (PbSe) particulate films, composed of highly oriented, equilateral triangular crystals, have been in situ generated by the exposure of arachidic‐acid‐ (AA) monolayercoated aqueous lead nitrate [Pb(NO3)2] solutions to hydrogen selenide (H2Se). The AA coated PbSe films, at different stages of their growth, were transferred to solid substrates and characterized by transmission electron microscopy (TEM), electron diffraction, and atomic force microscopy (AFM). The epitaxial growth of PbSe crystals has been rationalized in terms of matching the {111} plane of crystalline PbSe and the (100) plane of the hexagonally close‐packed AA monolayer. The parallel alignment of the ⩽110> and ⩽001> axes and the perpendicular alignment of the ⩽110> axis to the monolayer have been suggested to be responsible for the observed formation of rod‐like PbSe particles. The presence of a negatively charged monolayer has been found to be an essential requirement for the oriented growth of PbSe crystals. © 1994 Wiley‐Liss, Inc.
Liquid crystalline order of biopolymers in cuticles and bones
Authors: Giraud‐Guille Marie‐Madeleine 
Published: February 2005

AbstractMicroscopic studies at different scales have shown that in biological tissues the three‐dimensional arrangement of chitin‐protein or of collagen fibrillar networks can follow the same spatial distributions as those described in certain liquid crystals. The present work reviews the structural analogies established between the dense fibrillar organic matrix found in two materials: crab cuticles and compact bones. In both systems mobile fringes are described in polarizing microscopy, periodic cleavage aspects in scanning electron microscopy (SEM), and arced patterns in transmission electron microscopy (TEM). In parallel to these structural data, results obtained in vitro are recalled which corroborate the relationship established between ordered arrays of biopolymers and liquid crystalline assembly principles, highly concentrated solutions of purified collagen molecules spontaneously form ordered assemblies characterized in polarizing microscopy as cholesteric phases. This particular state of matter joins both fluidity and order and could correspond to a transient state of collagen or chitin secretion, before the stiffening of these skeletal structures, bone or cuticle, by molecular cross‐links and crystalline deposition. © 1994 Wiley‐Liss, Inc.
Investigations of monolayers by fluorescence microscopy
Authors: Stine Keith J. 
Published: February 2005

AbstractThe technique of fluorescence microscopy enables imaging of coexisting domains in Langmuir monolayers which have been doped with a small amount of a fluorescent probe. It is also possible to image surface aggregates formed by labeled proteins interacting with phosholipid monolayers. The method has provided information concerning phase behavior and structure of monolayers and proven useful in the study of monolayers as model systems of membrance processes. © 1994 Wiley‐Liss, Inc.
Molecular organization in phospholipid monolayer domains by correlative fluorescence microscopy and electron diffraction
Authors: Hui Sek Wen , Yu Hao 
Published: February 2005

AbstractLipid monolayer is a half leaflet model for lipid bilayer, which forms the basis of biological membranes. Within a certain range of surface area per molecule of phospholipid monolayers at the air‐water interface, where the compressibility was nearly infinite, two phases with different molecular packings were observable by fluorscence microscopy. Mixed‐phase monolayers of L‐1,2‐dipalmitoyl‐N‐monomethyl‐3‐phosphatidylethanolamine [DP(Me)PE] or L‐1,2‐dipalmitoyl‐N‐dimethyl‐3‐phosphatidyl‐ethanolamine [DP(Me)2PE] were deposited on marker grids coated with Formvar films. The molecular organization in the dark and bright fluorescent areas on the grids was investigated by low dose, selected area electron diffraction. Sharp reflection arcs, at a spacing of 4.2Å and arranged in a hexagon pattern, were detected from dark domains of both lipids. A diffuse reflection ring at a spacing of 4.6Å was derived from the bright background areas. Diffraction patterns were obtained from neighboring areas along selected dark domains of both lipids. The orientations of diffraction patterns from areas along smooth and curving boundries of DP(Me)2PE domains were found to turn with the boundaries. In the branching domains of DP(Me)PE, the orientations of diffraction patterns indicated that the branches were formed by twinning. Electron diffraction thus provides an unique way to sample the local molecular packing order and orientation within individual domains in phospholipid monolayers. © 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.
Quantitation of blood‐brain barrier ultrastructure
Authors: Stewart P. A. , Hayakawa K. , Farrell C. L. 
Published: February 2005

AbstractThis paper describes a quantitative approach to evaluating the ultrastructural features of brain capillaries that relate to the low non‐specific permeability of the blood‐brain barrier (BBB). Critical features in this approach include examination of large numbers of tissue samples and consistent, objective means of measuring features of interest. Junctional clefts, i.e., continuous channels between tight junctional regions correlate well with the know vascular permeability, being low in normal adult blood‐brain barrier, high in fetal brain, and high in tumours, both human and rat. Endothelial vesicles do not always correlate with vascular permeability. They have a low density in normal adult BBB, but are also low in fetal BBB and low in some intracranial tumour vessels. However, they have a high density in muscle capillaries, and others have shown that they increase in BBB vessels damaged by hypertension. Fenestrations are consistently high in leaky vessels, but not all leaky vessels have fenestrations. The density of mitochondria in endothelial cells is high in BBB vessels of some species but not in others. Glut‐1, the glucose transporter of the BBB is asymmetrically distributed between the luminal and abluminal membranes of BBB capillaries, being almost four times as numerous on the abluminal face. A large intracellular pool of glucose transporter may provide a means for rapid upregulation of the surface transporters. © 1994 Wiley‐Liss, Inc.
Permeability of the blood‐brain barrier induced by 915 MHz electromagnetic radiation, continuous wave and modulated at 8, 16, 50, and 200 Hz
Authors: Salford Leif G. , Brun Arne , Sturesson Kerstin , Eberhardt Jacob L. , Persson Bertil R. R. 
Published: February 2005

AbstractBiological effects of electromagnetic fields (EMF) on the blood‐brain barrier (BBB) can be studied in sensitive and specific models. In a previous investigation of the permeability of the blood‐brain barrier after exposure to the various EMF‐components of proton magnetic resonance imaging (MRI), we found that the exposure to MRI induced leakage of Evans Blue labeled proteins normally not passing the BBB of rats [Salford et al. (1992), in: Resonance Phenomena in Biology, Oxford University Press, pp. 87–91].In the present investigation we exposed male and female Fischer 344 rats in a transverse electromagnetic transmission line chamber to microwaves of 915 MHz as continuous wave (CW) and pulse‐modulated with repetition rates of 8, 16, 50, and 200 s−1. The specific energy absorption rate (SAR) varied between 0.016 and 5 W/kg.The rats were not anesthetized during the 2‐hour exposure. All animals were sacrificed by perfusion‐fixation of the brains under chloral hydrate anesthesia about 1 hour after the exposure. The brains were perfused with saline for 3–4 minutes, and thereafter fixed in 4% formaldehyde for 5–6 minutes. Central coronal sections of the brains were dehydrated and embedded in paraffin and sectioned at 5 μm. Albumin and fibrinogen were demonstrated immunohistochemically.The results show albumin leakage in 5 of 62 of the controls and in 56 of 184 of the animals exposed to 915 MHz microwaves. Continuous wave resulted in 14 positive findings of 35, which differ significantly from the controls (P = 0.002). With pulsed 915 MHz microwaves with repetition rates of 200, 50, 16, and 8 s−1, 42 of 149 were positive, which is highly significant at the P = 0.001 level. This reveals that both CW and pulsed 915 MHz microwaves have the potential to open up the BBB for albumin passage. However, there is no significant difference between continuous and pulsed 915 MHz microwaves in this respect.The frequency of occurrence of extravasates (26%) was found to be independent of SAR for SAR < 2.5 W/kg, but rose significantly for the higher SAR values (to 43%).The question of whether the opening of the blood‐brain barrier constitutes a health hazard demands further investigation. © 1994 Wiley‐Liss, Inc.
Electron microscopy of the blood‐brain barrier in disease
Authors: Hirano Asao , Kawanami Toru , Llena Josefina F. 
Published: February 2005

AbstractThe anatomical site of the blood‐brain barrier (BBB) is at the capillary endothelium mainly, with some contribution from astrocytes. Electron microscopic observations of endothelial cells and perivascular astrocytes comprising the BBB in brain edema and other pathological conditions are reviewed in this article. The tight junctions of cerebral endothelial cells open under several conditions such as infusion of hyperosmolar solutions. Pinocytotic vesicles increase under various pathological conditions and fenestrae appear in blood vessels of certain brain tumors and several non‐neoplastic lesions. Inflammatory cells penetrate between or through endothelial cells. In long standing lesions, endothelial cells containing various tubular structures such as Weibel‐Palade bodies proliferate. Other alterations include surface infoldings of endothelial cells and fluid diffusion through damaged endothelium. Astrocytic alterations include abnormal junctions between astrocytic processes in certain gliomas. In vivo and in vitro studies suggest that astrocytes maintain or develop certain functions of BBB. As the BBB is disrupted, edema fluid infiltrates the brain parenchyma. Because the white matter consists of nerve fibers without demonstrable junctions, it invades between nerve fibers. In the gray matter, expansion of the fluid is limited by complicated anatomical structures. In myelinated nerve fibers, edema fluid accumulates in five separate compartments of extracellular space. © 1994 Wiley‐Liss, Inc.
Basic structure of basement membranes is a fine network of “cords,” irregular anastomosing strands
Authors: Inoue Sadayuki 
Published: February 2005

AbstractA three‐dimensional network of irregular anastomosing strands, referred to as “cords,” was found to be the main component of the lamina densa of (a) common, “thin” basement membranes in tissues from diverse origins including foot pad epidermis, trachea, jejunum, seminiferous tubule and vas deferens of the rat, monkey seminiferous tubule, and mouse ciliary process, (b) a “double” basement membrane, the rat glomerular basement membrane, and (c) “thick” basement membranes including rat Reichert's membrane, mouse lens capsule and the Engelbreth‐Holm‐Swarm (EHS) tumor matrix. The average thickness of the cords was 3.2–4.8 nm, 4 nm, and 4.7–5 nm, respectively, in these three types of basement membranes. The mean diameter of the intercordal spaces, or openings of the network, averaged 14 nm with a range from 8 nm in the glomerular basement membrane to 21.9 nm in the lens capsule. After cryofixation followed by freeze substitution or freeze drying, similar cord networks were observed in all basement membranes examined which included two thin basement membranes, that of the rat epididymis and seminiferous tubules, and three thick basement membranes, that is, the lens capsule and the EHS tumor matrix of the mouse, and rat Reichert's membrane. In addition, following the co‐incubation of laminin, type IV collagen and heparan sulfate proteoglycan at 35°C, a precipitate was formed which was found to contain lamina densa‐like sheets and large semisolid masses. Both types of structures were found to be made up of a network of 3 nm wide cords, which resembled that of natural basement membranes. With the immunoperoxidase technique, these cords were stained for major basement membrane components including laminin, type IV collagen, heparan sulfate proteoglycan, entactin, and fibronectin. Ribbon‐like “double tracks” 4.5 nm in width and being distributed along cords have been identified as the form taken by heparan sulfate proteoglycan in basement membranes. Following mild plasmin treatment, most of the cord components were digested away leaving behind a network of fine filaments found to contain type IV collagen. Each cord, therefore, is organized by a type IV collagen core filament which is surrounded by a plasmin‐sensitive sheath containing other basement membrane components. Two types of minor structural components, that is, 7–10 nm wide straight “basotubules” and 3.5 nm wide particulate structures referred to as “pentosomes” were associated with cord network in some basement membranes. In summary, since a fine network of about 4 nm thick cords was always found to occupy a bulk of all basement membranes examined in tissues of a diverse origin and of different species, and also after the use of different preparative methods, such cord network is likely to be the basic structure of basement membranes. © 1994 Wiley‐Liss, Inc.
Scanning and transmission electron microscopic studies of normal and diabetic acellular glomerular and retinal microvessel basement membranes
Authors: Carlson Edward C. 
Published: February 2005

AbstractBasement membranes (BMs) were first described in the mid‐19th century, but they were not isolated and prepared for compositional studies until nearly 100 years later. Early methods of isolation were carried out on renal glomeruli, which were first sub‐fractionated from kidney tissues by sieving. BMs were then isolated from the glomeruli by ultrasonic disruption, which, following low speed centrifugation, yielded “purified” but highly fragmented BM material. In an effort to obviate the mechanical damage to BMs produced by ultrasound, a sequential detergent solubilization technique was introduced that resulted in morphologically intact BMs from a variety of tissue sub‐fractions. This was highly advantageous because “acellular” BMs produced by the procedure could be examined critically by light and electron microscopic methods. Subsequently, this procedure has been utilized to demonstrate the substructural heterogeneity of vascular and non‐vascular BMs from a wide variety of animal species. The current review describes the results of scanning and transmission electron microscopic studies of acellular BMs prepared from renal glomeruli and from the retinal microvessels of the eye. These BMs are of particular interest to basic scientists and clinicians because they are altered in several disease states, most notably diabetes mellitus. An effort is made to point out the implications of glomerular and retinal vessel BM changes to the pathogenesis of diabetic kidney and retinal vessel BM disease. © 1994 Wiley‐Liss, Inc.
The glomerular basement membrane in lupus nephritis
Authors: Bruijn Jan A. 
Published: February 2005

AbstractSystemic lupus erythematosus is a disease that is particularly suited for studies of glomerular basement membrane pathology. Classification of the renal pathology of lupus nephritis is usually based on light microscopic features, combined with immunofluorescence findings and electron microscopic alterations. Study of renal biopsy helps to distinguish potentially reversible and irreversible disease, and to estimate prognosis of patients with lupus nephritis. Moreover, studies of human disease, as well as the availability of animal models and in vitro cell culture systems employing biochemical and molecular biological studies of extracellular matrix, have led to a considerable increase in knowledge of the pathogenetic events underlying derangements of the glomerular basement membrane in lupus nephritis. © 1994 Wiley‐Liss, Inc.