bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogeny of platelet‐derived growth factor receptor in fetal rat lung
Authors: Han Robin N. N. , Liu Jason , Tanswell A. Keith , Post Martin
Published: February 2005

There is increasing evidence that platelet‐derived growth factor (PDGF) or PDGF‐like molecules play a role in fetal lung morphogenesis. Our previous studies demonstrated the presence of PDGF‐AA and PDGF‐BB homodimers in fetal rat lung. To study further the target cells of PDGF in lung development, immunolocalization studies of PDGF receptors (PDGFR) were conducted on embryonic and fetal rat lung from day 13 to day 21 of gestation (term = 22 days) using two polyclonal PDGFR antibodies, one of which one recognizes both α and β receptors (PDGFR‐α/β), while the other is specific for the β receptor (PDGFR‐β). A similar immunostaining pattern for both antibodies was noted. Immunoreactivity to PDGFR was evident in both epithelial and mesenchymal cells of the embryonic lung bud as early as 13 days gestation. The number of PDGFR immunoreactive cells increased with advancing gestation. Intense immunoreactivity was noted in both epithelial cells and interstitial cells during the saccular stage of lung development. The immunoreactivity to PDGFR was localized to the apical/luminal side of bronchial and distal airway epithelial cells. PDGFR‐immunopositive bronchial and vascular smooth muscle cells were detected only during the canalicular and saccular stages of lung development. Immunopositive endothelial cells lining the internal vascular plexuses were observed from days 14–16 of gestation. No PDGFR was detected in endothelial cells of large pulmonary vessels. We conclude that PDGFR are present in airway epithelial cells, interstitial cells, and bronchial and vascular smooth muscle cells and that gestation‐dependent up‐ and down‐regulation of PDGFR may play a role in developmental regulation of PDGF bioactivity during lung morphogenesis. © 1993 Wiley‐Liss, Inc.
Pathology of the salivary glands: The contribution of electron microscopy
Authors: Dardick Irving , Burford‐Mason Aileen P.
Published: February 2005

Electron microscopy has a limited role in the diagnosis of primary salivary gland tumors, although it can be helpful in metastatic lesions of possible salivary gland origin. The diversity of subtypes in salivary gland tumors, as well as the range of histomorphology within any one subtype, is unparalleled in any other human tumor. This and their relative infrequency causes diagnostic problems for pathologists. Ultrastructural techniques have been of major importance in determining the inter‐relationship of these tumors for classification purposes, revealing the subtle variations in common cellular differentiation pathways, determining the organization of tumor cells, and displaying the importance of extracellular matrix materials in establishing diagnostic criteria for each of the many subtypes. Electron microscopy has also been valuable in non‐neoplastic salivary gland disease and has an increasing role in experimental studies involving tissue from human and animal salivary parenchyma. © 1994 Wiley‐Liss, Inc.
Plasticity of cell organization during differentiation of normal and oncogene transformed granulosa cells
Authors: Amsterdam A. , Aharoni D.
Published: February 2005

Granulosa 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

Our 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

Cytochrome 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

Effective 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

Lead 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

Microscopic 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

The 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

Lipid 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

This 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

Biological 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

The 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

A 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

Basement 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

Systemic 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.
Ischemia‐Induced delayed‐onset paraplegia is accompanied by an unusual form of synaptic degeneration in the lumbosacral segments: An experimental light and electron microscopic study in dogs
Authors: Marsala Joseph , Marsala Martin , Sulla Igor , Burda Joseph , Galik Jan , Orendacova Judita
Published: February 2005

We studied the effect of high thoracic aorta cross‐clamping, complete transverse section of the spinal cord at Th6 level, and combined hemisection at Th6 level followed later by high thoracic aorta cross‐clamping upon the morphology and number of identified presynaptic knobs in lumbosacral segments in dogs. In animals surviving 48‐72 hours after high thoracic aorta cross‐clamping the occurrence of an unusual form of boutons accompanied by periboutonal halo in L3‐S1 segments was found. According to the bouton size and light as well as electron microscopic appearance, four types, i.e., light giant (T1), dark enlarged (T2), light giant with periboutonal halo (T3), and giant disintegrating (T4) boutons were detected after 48 and 72 hour reperfusion. The appearance of four boutonal types in the lumbosacral segments is caused by spinal cord ischemia secondary to high thoracic aorta cross‐clamping followed by 48 or 72 hour reperfusion. At the end of the sixth reperfusion day no signs of enlarged and giant boutons were detected in L3‐S1 segments. A statistically significant increase of enlarged and giant boutons was noted at the end of the third reperfusion day in comparison with 48 hour survival. After spinal cord transection at midthoracic (Th6) level, followed by 72 hour survival, no such unusual synaptic knobs could be found in L3‐S1 segments. The laminar distribution pattern of T1‐T4 types based on light microscopic analysis and confirmed electron microscopically is characteristic and strictly bound to those spinal cord gray matter layers which serve as main termination sites of the descending cortical, brain stem, as well as long propriospinal projections in the lumbosacral segments (laminae V‐VIII). A statistically significant increase of enlarged and giant boutons was found in the intermediate zone (lamina VII). Hemisection at midthoracic level (Th6) followed later by 30 minute high thoracic aorta cross‐clamping and 48 hour reperfusion caused a marked decrease of enlarged and giant boutons in L3‐S1 segments on the hemisectioned side in comparison with the contralateral one. Large amounts of irregularly arranged round vesicles and tubular profiles were disclosed in the boutonal matrix of T1, T3, and T4 types in L3‐S1 segments of animals subjected to 30 minute high thoracic aorta cross‐clamping followed by 72 hour reperfusion. Accumulation of tubular and membranous materials was invariably seen in the bulbous enlargement of the terminal axonal branch. Therefore, it is reasoned that the ischemia‐induced delayed‐onset paraplegia is closely related to synaptic uncoupling, resulting after ischemia‐reperfusion damage of the spinal cord interneurons acting as postsynaptic neurons for long descending spinal cord afferents of cortical and brain stem origin. © 1994 Wiley‐Liss, Inc.
Structural and functional changes in salivary glands during aging
Authors: Kim Sun‐Kee , Allen Edward D.
Published: February 2005

Various salivary glands in senescent humans and other animals have been examined extensively to characterize the structural and functional changes that occur during aging. Although a wide range of different structural changes, involving both the parenchymal and stromal tissues, have been described, it is unclear how any of these changes affects the function of the salivary glands. One major change in structure is the reduction in the volume of acini with a concomitant increase in the ductal volume. Despite this loss of functional acini, the salivary output and the contents seem to be unaltered, or minimally altered, due to aging. One consistent change observed in many salivary glands of aged animals is the decline in the rate of synthesis of proteins and their messenger RNA (mRNA). However, the salivary acinar cells from aged animals can synthesize secretory proteins at an elevated rate just as effectively as those from their younger counterparts in response to external stimuli, which are known to enhance the rate of protein synthesis. Thus, it appears that the salivary acinar cells, which remain structurally intact during aging, seem to retain their functional efficiency. Furthermore, these acinar cells, although reduced in number, are sufficient in quantity to carry out most of the salivary gland functions. © 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.
Backscatter electron imaging of double immunogold labeled erythrocytes using two primary monoclonal IgM antibodies
Authors: Namork Ellen , Heier Hans Erik
Published: February 2005

The majority of mouse monoclonal antibodies reacting with blood group epitopes on erythrocytes are of the IgM class, have equal light chain type, and are available as culture supernatants only. To study the interrelationship of the blood group antigens, a method is presented which allows double labeling applying two unconjugated monoclonal antibodies of the same class and species. The method comprises two indirect, sequential labelings using mouse IgM anti‐A and anti‐H as primary antibodies and two goat anti‐mouse IgM conjugated to 30 and 20 nm colloidal gold particles as secondary antibodies. After labeling for the first antigen, free binding sites on the primary antibody are blocked by incubation with an unconjugated goat anti‐mouse antibody. The free anti‐species on the secondary antibody, conjugated to 30 nm gold particles, are inactivated by silver enhancement. The silver enhancement also enlarges the gold particle for optimal discrimination between the two particle sizes, which are chosen accordingly. Semiquantitations of double labeled cells from subgroup A2 and A3 were found to be in good agreement with the counts of the corresponding single labelings as well as between experiments, irrespective of which of the two antibodies was applied in the first labeling sequence. The results were in accordance with a reciprocal but nonlinear relationship between the A and H antigens and suggest different affinities of the two antibodies for the epitopes in the subgroups investigated, indicating different biochemistry of the antigen determinants. © 1994 Wiley‐Liss, Inc.
Combined use of immunocytochemical techniques and ligand‐gold complexes for investigation of platelet membrane responses to surface activation
Authors: Escolar Gines , White James G.
Published: February 2005

Exposure of blood platelets to foreign surfaces results in dramatic changes in physical appearance and conversion from a non‐sticky to an adhesive state. Membrane glycoproteins and cytoskeletal assembly play a pivotal role in these interactions. Cytochemical techniques commonly applied for demonstration of macromolecules in tissues have been used for the localization of target glycoproteins on spread cells. The present review examines different experimental strategies and immunocytochemical techniques that can be combined to better understand the organization of platelet receptors during surface activation. Glycoprotein IIb‐IIIa (GPIIb‐IIIa) was localized by immunocytochemical techniques on fixed, surface‐activated platelets. The distribution of functional fibrinogen receptors expressed on GPIIb‐IIIa was revealed by incubation of fixed platelets with fibrinogen‐gold conjugates (Fgn/Au). The movement of receptor complexes was investigated in additional experiments in which surface‐activated platelets were interacted with Fgn/Au and then fixed at different periods. The overall impression of these observations suggests that fibrinogen receptors on surface‐activated platelets do not redistribute spontaneously and that particulates (gold particles), rather than fibrinogen, may trigger the movement. These results are presented in detail and their significance discussed in the light of current theory. Applications and limitations of such techniques are also discussed. © 1994 Wiley‐Liss, Inc.
Programmed cell death of the normal human neutrophil: An in vitro model of senescence
Authors: Payne Claire M. , Glasser Lewis , Tischler Marc E. , Wyckoff Deborah , Cromey Douglas , Fiederlein Roger , Bohnert Oliver
Published: February 2005

The present study provides experimental data which indicate that the neutrophil is ideal for studying programmed cell death or apoptosis in vitro. Neutrophils can be obtained from human peripheral blood in large numbers with minimal experimental manipulation and are easily separated from other leukocytes, providing nearly pure cell suspensions. The neutrophil life span in vitro is sufficiently short to allow observations to be made within eight hours after experimental manipulation. Neutrophils can also be easily maintained in serum‐free, chemically defined media which can be systematically altered, thereby defining specific variables that influence the apoptotic process. Since the neutrophils do not need an exogenous trigger to undergo programmed cell death, it is also an excellent model to study senescence. It was determined from this study that neutrophils undergo apoptosis most efficiently at 37°C, a temperature requirement for physiologic cell death. Neutrophils undergo apoptosis at a slightly faster rate and maintain membrane integrity better when incubated in a tissue culture medium (e.g., RPMI 1640) compared with a balanced salt solution (e.g., HBBB). Cycloheximide, an inhibitor of protein synthesis, was shown to accelerate apoptosis in a dose‐dependent manner. The presence of Zn++ significantly decreased the rate of apoptosis, whereas the presence of Ca++ and Mg++ had no apparent effect. These studies indicate that the process of senescence, culminating in cell death, is subject to modulation by a variety of agents and experimental conditions. In addition, the ultrastructural features of neutrophils undergoing programmed cell death in vitro were compared in detail to those occurring in vivo and were found to be comparable. © 1994 Wiley‐Liss, Inc.
Cartilage proteoglycans: Structure and potential functions
Authors: Roughley Peter J. , Lee Eunice R.
Published: February 2005

Hyaline cartilage contains five well‐characterized proteoglycans in its extracellular matrix, and it is likely that others exist. The largest in size and most abundant by weight is aggrecan, a proteoglycan that possesses over 100 chondroitin sulfate and keratan sulfate chains. Aggrecan is also characterized by its ability to interact with hyaluronic acid to form large proteoglycan aggregates. Both the high anionic charge on the individual aggrecan molecules endowed by the sulfated glycosaminoglycan chains and the localization within the matrix endowed by aggregate formation are essential for aggrecan function. The molecule provides cartilage with its osmotic properties, which give articular cartilage its ability to resist compressive loads. The other proteoglycans are characterized by their ability to interact with collagen. They are much smaller than aggrecan in size but may be present in similar molar amounts. Decorin, biglycan, and fibromodulin are closely related in protein structure but differ in glycosaminoglycan composition and function. Decorin and biglycan possess one and two dermatan sulfate chains, respectively, whereas fibromodulin bears several keratan sulfate chains. Decorin and fibromodulin both interact with the type II collagen fibrils in the matrix and may play a role in fibrillogenesis and interfibril interactions. Biglycan is preferentially localized in the pericellular matrix, where it may interact with type VI collagen. Finally, type IX collagen can also be considered as a proteoglycan, as its α2(IX) chain may bear a glycosaminoglycan chain. It may serve as a bridge between the collagen fibrils or with the interspersed aggrecan network. © 1994 Wiley‐Liss, Inc.
Fine structure of Tritrichomonas foetus as seen using cryotechniques
Authors: Benchimol Marlene
Published: February 2005

Tritrichomonas foetus was studied using different physical and chemical fixation methods such as fast‐freezing (by high pressure, “slam‐freezing,” and jet‐propane), freeze‐substitution, conventional freeze‐fracture and deep‐etching, cryoultramicrotomy, and routine preparation for transmission electron microscopy. The use of fast‐freezing fixation (FFF) proved to be superior in terms of structural preservation due to the rapidity of this fixation compared to that obtained using conventional chemical fixation. The low temperature techniques used here were useful to confirm data already obtained by conventional freeze‐fracture using chemical fixation and cryoprotection, such as the presence of flagellar rosettes and costa structure. Cryoultramicrotomy and slam‐freezing also demonstrated the presence of hair‐like structures projecting out from the protozoan surface. New aspects of organelles of T. foetus were demonstrated. Published 1994 by Wiley‐Liss, Inc.
Nitric oxide synthase containing neurons in the carotid body and sinus of the guinea pig
Authors: Tanaka Koichi , Chiba Tanemichi
Published: February 2005

The morphology and function of the carotid sinus and carotid body have been extensively studied, but our knowledge of their transmitter(s) is still incomplete. Nitric oxide (NO) recently has been identified as a novel messenger molecule in a number of neuronal and non‐neuronal tissues. Nitric oxide synthase (NOS) has been demonstrated in many neurons of the autonomic nervous system. The present study examines the distribution of NOS in the carotid sinus and body. The carotid sinus and body of newborn guinea pigs were removed for histochemical examination of NOS using the NADPH‐diaphorase method. In the carotid body, many nerve fibers enveloping the glomus cells were positive for NOS. In addition, some glomus cells were positive for NOS. In the carotid sinus, NADPH‐d positive fibers were distributed unevenly in the adventitia and media. These results indicate the possibility that nitric oxide plays a role in both arterial chemoreception and baroreception. © 1994 Wiley‐Liss, Inc.
Chemosensitivity, plasticity, and functional heterogeneity of paraganglionic cells in the rat coeliac‐superior mesenteric complex
Authors: Borghini Nadine , Dalmaz Yvette , Peyrin Liliane , Heym Christine
Published: February 2005

Chemosensitivity and plasticity of paraganglionic cells in the rat coeliac‐superior mesenteric complex (CSMC) were investigated at a basal state of normoxia (21% O2) and after long‐term moderate hypoxia (10% O2, 14 days). Chemical sympathectomy previous to hypoxia was performed to destroy principal ganglionic neurons and thus to allow measurement of the norepinephrine and dopamine content of paraganglionic cells.

At the basal state, the CSMC contained dopaminergic (TH+/DBH−) and noradrenergic (TH+/DBH+) paraganglionic cells, the majority being of the noradrenergic type. After 14 days of hypoxia, this ratio was reversed and dopaminergic cells predominated, as indicated by a twofold increase of TH+cells and a twofold decrease of DBH+cells. Biochemically, hypoxia produced an increase in the content (1.6‐fold) and utilization (1.4‐fold) of dopamine as well as a smaller increase in the content of norepinephrine, with no change in its utilization rate. The dopaminergic activation induced by hypoxia persisted after sympathectomy with guanethidine.

It is concluded that paraganglionic cells in the CSMC display a chemosensitive function. Furthermore, our findings indicate that paraganglionic cells are differentially affected by hypoxia, depending on their distribution and the nature of their neuromodulators. The alterations induced by hypoxia point out the phenotypic plasticity developed by paraganglionic cells in adaptation to hypoxia and further demonstrate the functional heterogeneity of this autonomic cell population in the rat CSMC. © 1994 Wiley‐Liss, Inc.
Adrenal medulla in neural grafting and neural plasticity
Authors: Hansen John T. , Gash Don M.
Published: February 2005

The recent history of neural transplantation using the adrenal medulla parallels an evolution in our thinking about neural grafting as a therapeutic approach to treat neurodegenerative diseases such as Parkinson's disease. Initially, neural grafting was an approach to study development and regeneration. With the discovery that adrenal chromaffin cell grafts would ameliorate some of the motor deficits associated with the loss of striatal dopamine, adrenal grafts were used to provide dopamine to the dopamine‐depleted striatum. However, subsequent studies showed poor chromaffin cell survival unless trophic factors were present at the site of transplantation. These experiments lead to the appreciation of the complex interactions between neurotrophic factors, inflammatory cytokines, the grafted tissue, and the host brain's response. Thus, we find ourselves again using neural transplantation as an approach to help us better understand central nervous system plasticity and the features this plasticity shares in common with development and regeneration. © 1994 Wiley‐Liss, Inc.
Nitric oxide modulates sympathetic neurotransmission at the prejunctional level
Authors: Addicks K. , Bloch W. , Feelisch M.
Published: February 2005

In spite of accumulating evidence for a modulation of sympathetic neurotransmission by endogenously produced nitric oxide (NO), it remains unclear in which parts of the vascular system and at what level this interaction takes place. The aim of the present study was to investigate the distribution of endothelial and neuronal NO synthase (NOS) along the vascular tree of the heart at the light and electron microscopic level using NADPH‐diaphorase (NADPH‐d) staining as a marker for NOS. In addition, the functional effects of exogenous NO on coronary vascular resistance and cardiac adrenergic nerves was studied using the isolated perfused rat heart as a model. The intraaxonal catecholamine content of adrenergic nerve fibers was visualised and morphometrically assessed by applying glyoxylic acid‐induced histofluorescence. The expression of endothelial NOS in the heart was found to depend on the diameter of the blood vessel. Arteries >100 μm always showed intense staining, whereas staining in smaller arteries and veins was considerably weaker. Smooth‐muscle free vessels were essentially devoid of NADPH‐d activity. In atrial and ventricular myocardium, neuronal NOS localised in autonomic nerve fibers along the entire vascular tree. Ultrastructurally, NADPH‐d staining revealed adjacent localisation of NOS‐positive and ‐negative axons, suggesting an interaxonal modulation of adjacent autonomic nerve fibers by NO. In isolated perfused rat hearts, the intracoronary application of 10−8 M NO produced a marked decrease of coronary perfusion pressure, which was accompanied by a distinct increase in intraaxonal catecholamine levels of intramural adrenergic nerve fibers. These results suggest that the entire vascular system from arteries to veins is under the influence of NO and implies that two independently operating NO‐driven processes are involved in the modulation of blood vessel tone: the well‐known pathway of endothelium‐derived NO acting directly on smooth muscle, and a second indirect pathway that inhibits noradrenaline release from perivascular nerve endings by endothelially or neuronally produced NO. The uneven distribution of endothelial NOS furthermore suggests that the latter mechanism predominates when the size of the blood vessel decreases. © 1994 Wiley‐Liss, Inc.
Light microscopic distribution of some cholinergic markers in the rat and rabbit locus coeruleus and the nucleus angularis grisea periventricularis of the domestic pig (Sus scrofa): A correlative electron microscopic investigation of cholinergic receptor proteins in the rabbit
Authors: Caffé A. R.
Published: February 2005

Cholinergic modulation of locus coeruleus (LC) neurons evokes a variety of neuronal and behavioural effects. In an attempt to understand the LC cholinergic circuit, several markers has been investigated and compared. (Immuno)‐histochemical and autoradiographic methods have been used on rat, rabbit, and pig tissue. To identify the boundaries of the LC in each of these species, sections through the entire brainstem have been stained for tyrosine hydroxylase. The results that the pig does not possess a LC proper that conforms to the accepted features of this cell group. However, in this location fusiform cells reminiscent of LC interneurons are still present. This group of fusiform neurons has been named the nucleus angularis grisea periventricularis (NAGP).

LC cells of the rat and rabbit show strong acetylcholinesterase (AChE) activity. In the pig the NAGP is markedly free from AChE staining. Muscarinic binding sites are densely distributed over the rabbit LC and adjacent region. The rat and rabbit LC neurons synthesise both muscarinic (mAChR) and nicotinic receptor protein (nAChR). In the pig NAGP region mAChR and nAChR positive cell bodies are almost absent, while some nAChR immunoreactive dendrites are present. The light microscopic data in the rabbit have been confirmed by electron microscopic analysis.

It is concluded that the general concept of a noradrenergic LC that is present throughout mammals is questionable. At present, choline acetyltransferase immunoreactive terminals that closely correspond to the other cholinergic components in the rat or rabbit LC have not been observed. However, in these species the cholinergic sensitivity of LC cells is mediated via both muscarinic and nicotinic receptors on somata and dendrites. © 1994 Wiley‐Liss, Inc.