bluuebunny/crossref_metadata_2025_split huggingface dataset:
The innervation of salivary glands as revealed by morphological methods
Authors: Garrett John R. , Kidd Audrey 
Published: February 2005

AbstractSalivary secretion is nerve mediated. The salivary glands are supplied by parasympathetic and sympathetic efferent nerves which travel to the glands by separate routes. Once in the glands the axons from each type of nerve intermingle and travel together in association with Schwann cells, forming Schwann‐axon bundles. Two types of neuro‐effector relationships exist with salivary parenchymal and myoepithelial cells: epilemmal (outside the parenchymal basement membrane) and hypolemmal (within the parenchymal basement membrane). Their relative frequencies with either type of nerve differ greatly between glands and species. Salivary blood vessels receive epilemmal innervations by both sympathetic and parasympathetic axons. The classical transmitters—acetylcholine in parasympathetic and noradrenaline in sympathetic axons—are stored in small vesicles. A variety of non‐conventional neuropeptide transmitters have also been found in salivary nerves by immunohistochemistry, and they occur in large dense‐cored vesicles. Prolonged high frequency stimulation has been found to cause depletion of large dense‐cored vesicles from glandular nerves. In recent years afferent nerves have started to be identified and are found in greatest numbers around the main salivary ducts, where they may form a hypolemmal association with the epithelial cells. Functional studies demonstrate complex interactions between parasympathetic and sympathetic nerves. Morphological assessments of changes in the parenchymal cells after nerve stimulations or denervations add greatly to our understanding of the nerve functions. At least four types of influence can be exerted on salivary parenchymal cells by the nerves: hydrokinetic (water mobilizing), proteokinetic (protein secreting), synthetic (inducing synthesis), and trophic (maintaining normal functional size and state). In respect to each role, wide glandular and species differences exist between the relative contributions made by each type of nerve. © 1993 Wiley‐Liss, Inc.
Evolutionary modifications of morphogenetic mechanisms and alternate life history strategies in ascidians
Authors: Bates William R. 
Published: February 2005

AbstractComparative embryological studies using anural and urodele ascidians provide an experimental system to study interactions between developmental and evolutionary mechanisms that produce alternate life history strategies. In this paper, cellular features of anural morphogenesis in Molgula pacifica are compared to morphogenesis in species that develop tailed (urodele) larvae and other anural molgulid species. The results of these studies are discussed with regard to possible mechanisms responsible for the evolution of anural morphogenesis and the ecological consequences of anural development. Early developmental processes including ooplasmic segregation, cleavage patterns, and the site and timing of gastrulation were similar in M. pacifica compared to urodele embryos and embryos produced by other anural species. The limited extent of invagination caused by large, yolky cells that restricted vegetal pole cell movements in M. pacifica gastrulae contrasted with the extensive movements of vegetal pole cells that accompanied invagination in M. provisionalis embryos and the embryos of four urodele species. The modified mode of gastrulation exhibited by M. pacifica embryos is likely due to the relatively high yolk content of their eggs.The developmental fates of muscle and epidermal progenitor cells in M. pacifica embryos were altered compared to urodele embryos. Ultrastructural studies and acetylcholinesterase histochemistry experiments indicate that muscle progenitor cells have lost their potential to develop muscle cell features. This loss in myogenic potential suggests that muscle progenitor cells were re‐programmed to die. However, this possibility was not supported by the results of ultrastructural studies. A second possibility is discussed in that muscle progenitor cells may have been re‐specified to differentiate into adult cells after metamorphosis. Evidence is presented suggesting that the timing mechanism responsible for controlling the onset of metamorphosis, first evident by the outgrowth of epidermal ampullae, was modified in M. pacifica. This paper concludes with a discussion of how anural morphogenesis altered the ancestoral urodele life cycle and the possible ecological benefits of these evolutionary alterations. © 1993 Wiley‐Liss, Inc.
Ultrastructural features of alveolar epithelial cells in the late fetal pulmonary acinus: A comparison between normal and hypoplastic lungs using a rat model of pulmonary hypoplasia and congenital diaphragmatic hernia
Authors: Brandsma Annelies E. , Tibboel Dick , Vulto Irma M. , Egberts Johannes , Ten Have‐Opbroek Ank A. W. 
Published: February 2005

AbstractThe aim of this study was to describe and compare the ultrastructural features and functional maturity of alveolar epithelial cells in hypoplastic and normal fetal rat lungs. Pulmonary hypoplasia in association with congenital diaphragmatic hernia was induced in fetuses by administration of 2,4‐dichlorophenyl‐p‐nitrophenylether (Nitrofen) to pregnant Sprague Dawley rats (100 mg on day 10 of gestation). Lung tissue of Nitrofen‐exposed and control fetal rats aged 19–22 days (vaginal plug day 1, birth day 23) was embedded in Epon. Semithin (1 μm) toluidine blue‐stained sections were examined by light microscopy; ultrathin sections (∼80 nm) were studied via transmission electron microscopy. In bronchoalveolar lavage fluid from control and Nitrofenexposed fetuses (day 22), phospholipid fractions and surfactant protein A content were measured semiquantitatively. On day 19 both control and Nitrofen‐exposed lungs contained only cuboid alveolar epithelial cells; from day 20 there were cuboid, low cuboid, and thinner epithelial cells. The (low) cuboid cells contained large glycogen fields, some precursory stages of multilamellar bodies (MLBs), and just a few mature MLBs on day 19 and 20; smaller glycogen fields, more precursory stages, and more mature MLBs on day 21; and little or no glycogen but many precursory stages and mature MLBs on day 22. The thinner cells contained little or no glycogen and a few precursory stages of MLBs on days 20–22; very thin cells on day 22 contained neither glycogen nor any precursory stages of MLBs. MLBs and tubular myelin were seen in the lumens of future air spaces from day 20 onward. Nitrofen‐exposed lungs differed from control lungs in that inclusion bodies (IBs) were less numerous in (low) cuboid alveolar cells on days 19 and 20, and more glycogen was seen on day 22. In addition intra‐ and extracellular “MLBs” in exposed lungs more often had an unusual appearance, i.e., a confluent structure and higher electron density. However, despite morphologic differences, there was no clear difference in phospholipid composition and SP‐A content per mol phospholipid in bronchoalveolar lavage fluid. We conclude that morphologically hypoplastic lungs are less mature near term, without an apparent effect on surfactant composition. © 1993 Wiley‐Liss, Inc.
New aspects of microvascular corrosion casting: A scanning, transmission electron, and high‐resolution intravital video microscopic study
Authors: Aharinejad Seyedhossein , MacDonald Ian C. , Mackay E. Carole , Mason‐Savas April 
Published: February 2005

AbstractWe used intravital microscopy of small intestine and pancreas in order to show dynamic interactions between vascular wall and undiluted Mercox, because previous studies of ours have shown that Mercox diluted with monomeric methylmethacrylate penetrates cells in the vascular wall. Scanning and transmission electron microscopy were used to show three‐dimensional pathways and correlating tissue structures, which cannot be identified in vivo. The microvascular diameters were not altered when the vasculature was flushed with saline/dextran solution using perfusion pressures between 70 and 140 mm Hg, but, in circumscribed areas, contraction of vascular wall was observed immediately after Mercox injection. This phenomenon was carried out by endothelial cells; pericytes were never present at the site of constrictions. Extravasation, i.e., leakage of the resin into the surrounding tissue, occurred in circumscribed areas regardless of the applied perfusion pressure. The resin also filled routes, which were not perfused with blood before casting. Scanning microscopy of corresponding specimens showed flattened cast channels, with impressions of valves and endothelial cell nuclear imprints characteristic of lymphatics. These results show that undiluted Mercox is a stimulus for vascular cellular components and that it changes the vascular wall permeability, resulting in extravasation and filling of lymphatics. Transmission electron microscopy showed that large vessels were homogeneously filled with resin and that cellular structures were not infiltrated with Mercox. Cut sections of the gold‐coated surface of casts showed grooves up to 20 nm wide, suggestive of minimal deformation, while the abluminal surface of the metal film was almost smooth. Another proof of minimal deformation of undiluted Mercox casts is that the diameter of vessels was not altered during and after polymerization. Obtained casts are not fragile, as are casts of diluted Mercox, and phase separation does not occur, which would result in penetration of the cells in the vascular wall. For these reasons, the use of undiluted Mercox is recommended. Mixing 10 ml Mercox with 1 g catalyst resulted in complete polymerization within 5.5–7 min. This mixture can be used for casting biological specimens. © 1993 Wiley‐Liss, Inc.
Myoepithelium of salivary glands
Authors: Redman Robert S. 
Published: February 2005

AbstractIn salivary glands and other exocrine organs, there are starfish‐shaped cells that lie between the basal lamina and the acinar and ductal cells. These have structural features of both epithelium and smooth muscle cells, and so are called myoepithelial cells. Their functions include contraction when the gland is stimulated to secrete, compressing or reinforcing the underlying parenchymal cells, thus aiding in the expulsion of saliva and preventing damage to the other cells. They also may aid in the propagation of secretory and other stimuli. Their common developmental origin with the basal cells of the larger ducts is displayed in the mature glands by shared structural and immunohistochemical features, but most such basal cells do not have the distinguishing features of myoepithelial cells, such as myofibrils. Although myoepithelial cells can be identified by light microscopy through enzyme histochemistry and special stains and immunohistochemistry for their myofibrils, these techniques can be misleading in salivary gland neoplasms. Thus, the most reliable means of identifying neoplastic myoepithelial cells is with a combination of histochemistry and electron microscopy. The extent to which these cells are derived from undifferentiated stem cells in both normal and neoplastic growth is controversial. The presentation here of transmission electron microscopy (TEM) of well‐differentiated myoepithelial cells in mitotic division indicates that stem cells are not necessarily the only source of myoepithelial cells in the later stages of salivary gland development or in neoplasia. © 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.
Patterns of intercellular connectivity in the mammalian cumulus‐oocyte complex
Authors: Albertini David F. , Rider Virginia 
Published: February 2005

AbstractElectron and fluorescence microscopic techniques have been used in a complementary fashion to study the patterns of follicle cell‐oocyte interactions within cumulus‐oocyte‐complexes of various mammals. The principal findings are: (1) two distinct types of transzonal processes exist that are distinguishable on the basis of cytoskeletal composition; (2) in some of the species examined (pig, goat, primate), corkscrew‐shaped processes rich in tubulin, traverse the zona pellucida and are invaginated into the oocyte cortex; (3) actin‐rich processes either ramify as a network at the outer surface of the zona pellucida or penetrate the zona and make contact with the oolemma in a species specific manner. These results are discussed with respect both to the need to employ complementary optical methods in assessing connectivity patterns within COC and to the possible role that extracellular matrix‐cell interactions play in the homeostatic control of oocyte growth and maturation. © 1994 Wiley‐Liss, Inc.
Variations in mitochondrial ultrastructure and dynamics observed by high resolution scanning electron microscopy (HRSEM)
Authors: Lea Peter J. , Temkin Robert J. , Freeman Karl B. , Mitchell Grant A. , Robinson Brain H. 
Published: February 2005

AbstractRat adrenal cortex was processed for high resolution scanning electron microscopy (HRSEM) to confirm tubular cristae, reported by transmission electron microscopy to be present in cortex mitochondria. Mitochondria in several other tissue and cell types were also observed and their ultrastructure confirmed by using three‐dimensional, stereo, high resolution scanning electron microscopy. The mitochondria in rat and human hepatocytes as well as human skin fibroblasts mitochondria proved to be long, up to 46 micrometers and branching, as compared to those in liver which were spherical in shape. Cold adapted brown fat cells were packed with mitochondria, these containing plate or shelf‐like cristae. Branched, rat striated muscle mitochondria were observed to curve around contractile protein filament bundles. The muscle mitochondrial cristae were found to be both tubular and plate‐like, within the same mitochondrion. The ratio of tubular cristae to plate‐like cristae varied considerably between muscle mitochondria. In order to use ultrastructural changes in mitochondria for differential diagnosis, and because 3D reconstruction of mitochondria based on transmission electron microscopy serial sections is severely limited in resolution, it is imperative to first develop a correct understanding of tissue specific, normal mitochondrial ultrastructure based on three‐dimensional, HRSEM methods. © 1994 Wiley‐Liss, Inc.
Electron microscopy of the F1F0 ATP synthase: From structure to function
Authors: Gogol Edward Peter 
Published: February 2005

AbstractThe 1F0 ATP synthase is the large multisubunit complex which uses the proton gradient of energetically active membranes to synthesize ATP. While biochemical and genetic approaches have characterized the composition of the enzyme and elucidated many details of its mechanism and assembly, electron microscopy has been the tool of primary importance in determining the arrangement of the many subunits which comprise the F1F0. The highly cooperative catalytic mechanism is tightly coupled to transmembrane proton translocation in a separate and rather distant sector of the complex. An understanding of this intricate process and its control requires an appreciation of subunit interactions, starting with their locations relative to one another. Electron microscopy has provided most of the available structural information on the F1F0, and recent applications of cryo‐electron microscopy have captured different functionally relevant configurations which may finally address longstanding questions about subunit rearrangement during the catalytic cycle. © 1994 Wiley‐Liss, Inc.
Blood barriers of the epididymis and vas deferens act asynchronously with the blood barrier of the testis in the mink (Mustela vison)
Authors: Pelletier R.‐Marc 
Published: February 2005

AbstractThe purpose of the present study was to determine whether the blood barrier of the epididymis and vas deferens acted synchronously or not with the blood barrier of the testis. The permeability of the blood‐epididymis and blood‐vas deferens barrier was tested in neonatal kit mink up to puberty and monthly in adult minks throughout the annual seasonal reproductive cycle. Attention was focused particularly on time intevals when the blood barrier of the testis has been documented to be permeable, namely, before puberty and during testicular regression in the adult. One of two electron‐opaque permeability tracers was perfused into the blood stream: horeseradish peroxidase (HRP) or lanthanum nitrate. The convoluted tube of the epididymis was divided into three anatomical regions: the caput, corpus, and cauda. The vas deferens was divided into proximal and distal regions. At birth and throughout puberty, the three regions of the epididymis and the two of the vas deferens showed a lumen and a competent blood barrier. In the adult, a lumen persisted in the epididymis and vas deferens throughout the annual seasonal reproductive cycle, and the blood barrier of the excurrent duct remained impermeable even when the blood barrier in the testis become momentarily permeable during testicular regression. When HRP was used to test the permeability of the blood‐tissue barrier of the excurrent ducts, no tracer deposits were observed on the lumenal surface of the epithelium. Conversely, when lanthanum served as the tracer, deposits of the probe were associated with microvilli and intracellular membranes despite impermeability of tight junctions. The data show that the lanthanum technique can yield false‐positive results. The findings also indicate that (1) a blood‐excurrent duct barrier is established before the blood‐testis barrier and (2) the two barriers act asynchronously. It is therefore plausible that they are modulated by distinct factors. © 1994 Wiley‐Liss, Inc.
An introduction to biomimetics: A structural viewpoint
Authors: Sarikaya Mehmet 
Published: February 2005

AbstractBiomimetics is a newly emerging interdisciplinary field in materials science and engineering and biology in which lesson learned from biology form the basis for novel technological materials. It involves investigation of both structures and physical functions of biological composites of engineering interest with the goal of designing and synthesizing new and improved materials. This paper discusses microarchitectural aspects of some structural biocomposites, presents microstructural criteria for future materials design and processing, and identifies areas of future research. © 1994 Wiley‐Liss, Inc.
Molecular‐weight factors affecting formation of the OBDD morphology in block copolymer blends
Authors: Spontak Richard J. , Smith Steven D. , Ashraf Arman 
Published: February 2005

AbstractBlock copolymers undergo self‐organization when the blocks are sufficiently incompatible, and generate a variety of periodic morphologies in the limit of strong segregation. An equilibrium morphology only recently added to the diblock copolymer phase diagram is the ordered bicontinuous double‐diamond (OBDD) morphology, which possesses a Pn3m space group. It has been observed over a very narrow composition range (ca. 4 vol%), thereby making it difficult to obtain in pure copolymers. This obstacle can, however, be surmounted by blending a copolymer with one of the parent homopolymers. In the present study, several symmetric poly(styrene‐b‐isoprene) diblock copolymers varying in molecular weight (M) have been blended with homopolystyrene to produce the OBDD morphology. Transmission electron microscopy is employed here to identify the morphologies in cryosections of each blend and reveals that, at intermediate molecular weights, the OBDD morphology is indeed observed. At low M, near the order‐disorder transition, however, a lamellar catenoid or disordered morphology is preferred. At the other extreme, high‐M blends are frustrated by molecular entanglements and adopt a cylindrical morphology. © 1994 Wiley‐Liss, Inc.
Insight into the regulation by second messenger molecules of the permeability of the blood‐brain barrier
Authors: Joó Ferenc 
Published: February 2005

AbstractRecent advances in our knowledge of the blood‐brain barrier have in part been made by studying the properties and function of cerebral endothelial cells in vitro. After an era of working with a fraction, enriched in cerebral microvessels by centrifugation, the next generation of in vitro blood‐brain barrier model systems was introduced, when the conditions for routinely culturing the endothelial cells were established. This review summarizes the results obtained mainly from this in vitro approach. Different elements of the intracellular signaling messenger systems have been detected in the course of our studies in the cerebral endothelial cells. It has been shown that the synthesizing enzymes of and substrate proteins for the second messenger molecules are present in the cerebral endothelial cells, and their activity and/or amount can change in pathological circumstances, i.e., during the formation of brain oedema. Pharmacological treatments interfering with the second messenger systems proved to be effective in the prevention of brain oedema formation. © 1994 Wiley‐Liss, Inc.
High resolution platinum‐carbon replication of freeze‐dried basement membrane
Authors: Ruben George C. , Yurchenco Peter D. 
Published: February 2005

AbstractHigh angle platinum/carbon (Pt/C) replication has proved to be a valuable tool in analyzing basement membrane structure in human amnion, bovine lens capsule, and the Engelbreth‐Holm‐Swarm (EHS) tumor. High resolution replicas for transmission electron microscopy (TEM) have been achieved by depositing 1.0 ± 0.1 nm thick Pt/C films backed with rotary deposited 12.5 ± 2.5 nm thick carbon films. The basement membrane collagen IV network was observed to consist of fine branching filaments containing globular domains intrinsic to the filaments. A second quasi‐regular network is formed by laminin. Unidirectional 45° angle Pt/C replication was used for most of this work. The merits and deficiencies of unidirectional vertical replication (80° angle), unidirectional 45° angle, and 20° low angle rotary replication are discussed. Vertical replication produces the highest resolution replicas and has the potential for revealing the overall pattern of basement membrane structural assembly if basement membrane preparations freeze‐dried in low salt can faithfully maintain their in vivo structure. © 1994 Wiley‐Liss, Inc.
The borderline: Basement membranes and the transition from premalignant to malignant neoplasia
Authors: Bosman Fred T. 
Published: February 2005

AbstractIn this paper, the use of immunohistochemistry for the analysis of basement membrane components and related extracellular matrix proteins in human cancer is reviewed. Basement membranes in cancer are dynamic structures that are constantly degraded but also deposited, in close collaboration between tumor cells and stromal cells. Basement membrane immunohistochemistry, using antibodies against type IV collagen and laminin, appears to be a useful tool in the analysis of lesions on the borderline between premalignant and malignant. Basement membrane interruptions, however, cannot be used as the only criterion for the diagnosis of malignancy. Type VII collagen is often degraded prior to type IV collagen and laminin in early invasion. This protein also tends to be expressed in carcinomas when it is not found in the corresponding normal tissue. Tenascin seems to play a complex role in the development of human tumors, including promotion of cell growth and differentiation, cell migration during invasion, and tissue remodeling during the development of primary and metastatic lesions. Further systemic exploration of extracellular matrix molecules in neoplasms should yield new information relevant for cancer biologists and useful in cancer diagnosis. © 1994 Wiley‐Liss, Inc.