bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gastrulation in the mouse embryo: Ultrastructural and molecular aspects of germ layer morphogenesis
Authors: Tam Patrick P. L. , Williams Elizabeth A. , Chan W. Y. 
Published: February 2005

AbstractUltrastructural studies and lineage analyses of gastrulating mouse embryos have revealed that differnt morphogenetic tissue movements are involved in the formation of the three definitive germ layers. Definitive ectoderm is formed by epibolic expansion of the pre‐existing progenitor population in the embryonic ectoderm. Formation of the mesoderm and the endoderm is initiated by cellular ingression at the primitive streak. The mesodermal layer is established by cell migration and cell sheet spreading, but the endoderm is formed by replacing the original primitive endodermal population. To this date, genes that are expressed during mouse gastrulation mostly encode cell surface adhesion or signalling molecules, growth factors and their receptors, and putative transcriptional factors. Their precise role during gastrulation remains to be investigated. © 1993 Wiley‐Liss, Inc.
Morphogenesis of the avian trunk neural crest: Use of morphological techniques in elucidating the process
Authors: Erickson Carol A. 
Published: February 2005

AbstractMorphological data generated from light and electron microscopy form the basis of our understanding of avian morphogenesis. Because chicken embryos are readily and cheaply obtained and are easily accessible for experimental manipulation, morphogenetic processes have been studied extensively in this species. Such studies have allowed us to identify the cells involved during morphogenesis, observe the shape changes or cellular translocations that accompany a morphogenetic process, and determine the timing of these events. Elucidation of the molecular basis of morphogenesis has awaited the integration of several additional approaches. Among these are experimental embryology, which has allowed us to understand cellular behavior associated with morphogenesis; immunocytochemistry, which has identified the macromolecular cues that regulate cell movements and the environmental factors that control them; and molecular techniques, which will permit us eventually to clarify the genetic regulation of morphogenesis. Although current research in development is heavily biased towards molecular biology, morphological studies continue to frame the questions that are now being addressed using molecular techniques.This review focuses on the cells of the neural crest as a model system where questions of avian morphogenesis have been profitably addressed. © 1993 Wiley‐Liss, Inc.
Clara cell differentiation in the mouse: Ultrastructural morphology and cytochemistry for surfactant protein A and clara cell 10 kD protein
Authors: Ten Have‐Opbroek Ank A. W. , De Vries Erwin C. P. 
Published: February 2005

AbstractThe morphologic and functional differentiation of the nonciliated columnar (Clara) cell, one of two secretory cell types in distalmost bronchioles in mammals, was studied in the mouse. Lungs from embryos (16–19 days of developmental age, dDA; birth on day 19), postnatal animals (5–20 days postnatally dPN), and adult animals were investigated by transmission electron microscopy, using standard staining procedures and immunogold (GAR‐Au10) labeling for SP‐A and Clara cell 10 KD antigen (CCA). At 16 dDa, all the columnar epithelial cells lining prospective distalmost bronchioles lacked distinctive features. By 17 dDa, some cells displayed a few cilia or apical dense granules. At 18 dDa, many nonciliated columnar cells had apical protrusions, as are seen in adult Clara cells. Apical concentrations of glycogen observed in nonciliated columnar cells perinatally were absent by 5 dPN, whereas apical dense granules became more abundant. Profiles of smooth and rough endoplasmic reticulum (ER), which had been randomly distributed, exhibited a selective, adult distribution at 20 dPN (apical vs. basal cytoplasmic domains). Labeling for SP‐A and CCA, which was almost absent between 17 and 19 dDa, reached adult levels at the same time. The two proteins differed in distribution. SP‐A predominated in adluminal cytoplasmic areas, where it was found over dense granules, vesicles, and multivesicular bodies; it was also present in bronchiolar lumens and intercellular spaces but not in rough ER or Golgi apparatus. In contrast, CCA showed a more uniform distribution; it was present over the same structures as SP‐A and in the synthetic organelles. Ciliated columnar cells were virtually devoid of SP‐A and CCA. We conclude that mouse Clara cells acquire a mature phenotype by 20 dPN. They are likely to be involved in recycling and/or degradation of SP‐A that is internalized from airway lumens through their apical or lateral cell borders; furthermore, they synthesize the Clara cell 10 kD protein. These two Clara cell functions (first detectable late prenatally) reach mature levels by 20 dPN. © 1993 Wiley‐Liss, Inc.
Role of alveolar macrophage chemotaxis and phagocytosis in pulmonary clearance responses to inhaled particles: Comparisons among rodent species
Authors: Warheit David B. , Hartsky Mark A. 
Published: February 2005

AbstractAlveolar macrophages (AM) play an important role in clearing inhaled particles from the lung. The mechanisms through which macrophages identify particles that have been deposited in the alveolar regions is not well understood, although macrophage motility and phagocytic functions appear to be prerequisites for efficient clearance of inhaled materials. In previous studies, we assessed the mechanisms of macrophage‐mediated clearance of inhaled particles using a rat model. In this regard, it appears that one mechanism by which rat alveolar macrophages are recruited to sites of particle or fiber deposition is through complement activation and consequent generation of chemotactic factors by the inhaled particulates. Whether this mechanism is operative in other rodent species remains an unanswered question. The current studies were undertaken to compare pulmonary clearance responses in several rodent species exposed to carbonyl iron (CI) particles. In vitro and in vivo pulmonary clearance responses were evaluated using one strain each of mouse, hamster, rat, and guinea pig. In vitro studies showed that hamster AM had the greatest phagocytic activity and that rat AM migrated best to complement‐dependent chemotactic factors. Subsequently, groups of animals from each species were exposed to CI particles for 1 or 6 hr at aerosol concentrations of 100 mg/m3. Particle deposition patterns in the distal lung were nearly identical for all species, although enhanced numbers of CI particles were deposited on alveolar duct bifurcations of either rats or mice compared to hamsters, and particle deposition in guinea pigs was substantially lower. Time course studies showed that enhanced numbers of rat AM migrated to deposition sites and phagocytized particles, and this correlated with increased numbers and percentages of phagocytic macrophages recovered by lavage (P <0.01). In vivo phagocytic rates were the lowest in the mouse, and this correlated with reduced phagocytic rates in vitro. It is concluded form these studies that the rat may be the most efficient rodent species in clearing inhaled iron particles. In addition, it is conceivable that hamster AM are recruited to sites of particle deposition by a noncomplement‐mediated mechanism. © 1993 Wiley‐Liss, Inc.
Surfactant and inhaled particles in the conducting airways: Structural, stereological, and biophysical aspects
Authors: Gehr Peter , Geiser Marianne , Hof Vinzenz Im , Schürch Samuel , Waber Urs , Baumann Markus 
Published: February 2005

AbstractWe have investigated the displacement into the sol phase of inhaled particles deposited in the intrapulmonary conducting airways. Hamsters inhaled an aerosol of monodisperse polystyrene particles of 6 μm diameter. Their lungs were fixed by intravascular perfusion, and light and electron microscopy was used to study the epithelial coating. The surfactant film at the wall‐air interface was investigated by measuring its surface tension. The number of particles retained was determined stereologically. In addition we investigated the displacement of spherical particles in vitro on a DPPC monolayer in a Langmuir‐Wilhelmy surface balance and determined the surface tension in vivo in the horse trachea by video bronchoscopy, applying the droplet spreading method. We found that particles deposited onto a surfactant film were pulled into the aqueous subphase, and we concluded that surface forces due to the airway surfactant likely displace deposited particles into the periciliary fluid (sol phase). Comparing lungs fixed immediately after inhalation with lungs fixed 24 hr after inhalation revealed that 86% of the particles retained in the intrapulmonary conducting airways immediately after inhalation had been cleared within 24 hr. One‐third of the particles of the lungs fixed immediately after inhalation was phagocytized. The combination of structural and stereological analyses with in vitro and in vivo measurements has led to new insights into the role of airway surfactant with respect to the fate of inhaled particles, which may have important consequences regarding the effects of hazardous particles, which may have important consequences regarding the effects of hazardous particles. These studies may also help to evaluate the deposition pattern and clearance of therapeutic particles, with important implications for their therapeutic use. © 1993 Wiley‐Liss, Inc.
In vivo effects of endotoxin on DNA synthesis in rat nasal epithelium
Authors: Harkema J. R. , Hotchkiss J. A. 
Published: February 2005

AbstractAirway inflammation in bacterial infections is characterized by the presence of neutrophils and often epithelial injury and repair. Release of endotoxin from bacteria may contribute to these processes. The purpose of this study was to determine the in vivo effects of repeated endotoxin exposure on DNA synthesis in rat nasal epithelium in the presence and absence of neutrophilic influx. Rats were intranally instilled, once a day for 3 days, with endotoxin or saline (controls). Before the first and third instillations, half of the saline and endotoxin‐instilled animals were depleted of circulating blood neutrophils by administering a rabbit anti‐rat neutrophil antiserum. Rats were sacrificed 6 or 24 h after the last instillation. Two hours prior to sacrifice, rats were intraperitoneally injected with bromodeoxyuridine (BrdU), an analog of thymidine that is incorporated in the nucleus of cells in the S‐phase of the cell cycle. Nasal tissues were processed for light microscopy and immunohistochemical detection of BrdU in nasal epithelial cells. The numbers of nasal epithelial cells, BrdU‐labeled epithelial nuclei, and neutrophils per millimeter of basal lamina in the epithelium lining the nasal turbinates in the proximal nasal passages were determined by morphometric analysis. We did not observe a neutrophilic influx in the nasal tissues of neutrophil‐depleted rats at 6 or 24 h after the last endotoxin instillation; however, the numbers of nasal epithelial cells and the BrdU‐labeling index were significantly increased compared to salineinstilled controls. In controls. In contrast, non‐neutrophil‐depleted rats instilled with endotoxin had a marked neutrophilic influx, but no significant differences in the number of nasal epithelial cells at 6 or 24 h, compared to controls. In addition, the BrdU‐labeling index in neutrophil‐sufficient rats was increased only 6 h after the last instillation, compared to controls. These results indicate that 1) endotoxin induces an increase in epithelial DNA synthesis that is neutrophil‐independent, and 2) without a neutrophilic influx, there is sustained epithelial proliferation, resulting in a hyperplastic epithelium after repeated endotoxin exposure. © 1993 Wiley‐Liss, Inc. © 1993 Wiley‐Liss, Inc. *This article is a US Government work and, as such, is in the public domain in the United States of America.
A step section method for full histopathological assessment of carcinogen‐affected target tissue during respiratory carcinogenesis
Authors: Hammond William G. , Teplitz Raymond L. , Benfield John R. 
Published: February 2005

AbstractStudies of carcinogenesis that are not limited to overt neoplasms but also involve evaluations of preneoplastic stages require histopathological assessment of the entire carcinogen‐affected tissue so that the true nature and sequence of the progressive process can be determined. The customary serial sectioning approach achieves this goal, but at an inordinate logistic cost. In studies of hamster bronchial carcinogenesis, a step section method was compared to a quasi‐random approach and to the customary serial section method. The step section method achieved the same diagnostic completeness as serial sectioning, but at a two orders of magnitude reduction in costs. © 1993 Wiley‐Liss, Inc.
Comparison of hexamethyldisilazane (HMDS), Peldri II, and critical‐point drying methods for scanning electron microscopy of biological specimens
Authors: Bray D. F. , Bagu J. , Koegler P. 
Published: February 2005

AbstractThree different drying methods, critical‐point drying (CPD), Peldri II, and hexamethyldisilazane (HMDS), were compared using representative animal( rat kidney, trachea, duodenum, lung, and red blood cells) and plant( leaves from ten species of monocotyledons and dicotyledons) specimens. All three drying methods produced identical results with animal specimens. Plant specimens showed signs of shrinkage regardless of which drying method was employed. The order of preservation quality from best to worst for leaves was CPD > Peldri II > HMDS, with the CPD method providing substantially better results in all but one case. Postfixation of leaves with osmium tetroxide resulted in poorer preservation in all instances. Peldri II caused complete extraction of leaf cuticular wax, while both both CPD and HMDS showed minimal extraction compared with samples air dried directly from acetone. These results indicate that HMDS provides a time‐saving and inexpensive alternative to CPD for animal specimens. Plant specimens, particularly those containing cells with large central vacuoles, are adequately preserved only with the CPD method. In addition, postfixation with osmium should be avoided when processing plant specimens for scanning electron microscopy. © 1993 Wiley‐Liss, Inc.
A method to detect areas high in sulfhydryl groups in mouse epithelium
Authors: Kawabe Thomas T. , Buhl Allen E. 
Published: February 2005

AbstractWe have recently modified a non‐fluorescent, non‐radioactive histochemical method to detect sulfhydryl (S‐H) groups in tissues. This method was originally intended to detect chloramphenicol acetyltransferase (CAT) in transgenic mice. Temporal developmental differences in the keratinization of mouse digits can be seen in the staining pattern of the skin about the toes of neonatal mice. The basal cells of the epidermis exposed to the air show intense staining while the epidermis that is still attached to an adjacent toe shows no staining. The degree of S‐H presence can be determined by the tissues' resistance to blocking of the S‐H groups by iodoacetic acid. Areas that contain very high numbers of S‐H groups still show staining following blocking by iodoacetic acid. We have found that this method shows clear differences in the S‐H distribution of various epithelium, including skin, hair, nails, and tongue epithelium. © 1993 Wiley‐Liss, Inc.
A review of electron probe X‐ray microanalysis studies of salivary gland cells
Authors: Izutsu Kenneth T. , Cantino Marie E. , Johnson Dale E. 
Published: February 2005

AbstractElectron probe X‐ray microanalysis (EPXMA) has now been successfully applied to several salivary gland preparations. This paper briefly reviews the principles underlying this technique and the specific sample preparation procedures which permit accurate measurement of elemental concentrations in the various intracellular spaces. Findings from salivary gland studies indicate that cytoplasmic and nuclear spaces of nonstimulated acinar cells have high concentrations of K and P, and low concentrations of Mg, Ca, and S; and that mature secretory granules have high concentrations of Ca and S, and relatively low concentrations of K and P. No consistent differences have been found between the elemental concentrations of mucous and serous secretory granules. In vivo and in vitro EPXMA studies of the elemental changes associated with secretory granule maturation indicate there are at least two stages in this process: an early stage during which granule S concentration increases in parallel with mass density as condensing vacuoles mature into secretory granules, and a late stage during which granule mass density and protein content increase with no further elemental concentration changes. Findings from other in vivo and in vitro studies indicate that secretory granule membranes are permeable to Na, K, and Cl ions because the granular concentrations of these elements are altered by electrochemical gradients. Recent EPXMA results indicate that cells stimulated with parasympathomimetic agonists have decreased K and Cl concentrations, and increased Na concentrations. Furthermore, the magnitude of these changes are quantitatively consistent with changes measured using radio‐isotope equilibration and other techniques. In contrast, cells stimulated with the β‐adrenergic agonist, isoproterenol, have increased concentrations of Na and Cl, but unchanged K concentrations. In terms of pathology, Na concentration is found to be elevated in secretory granules from labial salivary glands of patients with cystic fibrosis, but the pathophysiological consequences of this change are not known. Thus, studies utilizing EPXMA have obtained detailed and unique information about physiological and pathophysiological changes in elemental concentrations of intracellular organelles in salivary gland cells. © 1994 Wiley‐Liss. Inc.
Ontogeny of the cytoskeleton during mammalian oogenesis
Authors: Gallicano G. Ian , McGaughey Robert W. , Capco David G. 
Published: February 2005

AbstractMammalian oogenesis is a process which requires a variety of changes in the structure and function of the specialized female germ cell. Evidence suggests that the cytoskeleton may mediate several of these structural and functional changes. In this review we evaluate what is known of cytoskeletal function during oogenesis, with emphasis on specialized cytoskeletal features in mammals. Existing investigations suggest that the oocyte, as a highly specialized cell, contains unique cytoskeletal elements which exhibit functions restricted to the process of early development. © 1994 Wiley‐Liss, Inc.
Ultrastructural changes during meiotic maturation in mammalian oocytes: Unique aspects of the human oocyte
Authors: Sathananthan A. Henry 
Published: February 2005

AbstractThis paper reviews the process of peri‐ovulatory oocyte maturation and the ultrastructural organization of the human egg and compares it with that of the mouse. The main thrust of the paper is on the human, since there are several reviews on the mouse. Both preovulatory and postovulatory events at fertilization, as well as some of the aberrant features of maturation are covered. Some changes induced by oocyte culture and cooling in the human are also included. The report attempts to focus on unique features of the human oocyte and shows a variety of ultrastructural differences between human and murine oocytes, which may well reflect differences in their physiology and biochemistry. Based on these differences and further observations on the process of fertilization of both species, particularly with respect to the inheritance of paternal centrioles, it is concluded that the mouse may not be a suitable modle for the development and refinement of current procedures in human assisted reproductive technology. © 1994 Wiley‐Liss, Inc.
The internal compartmentation of rat‐liver mitochondria: Tomographic study using the high‐voltage transmission electron microscope
Authors: Mannella Carmen A. , Marko Michael , Penczek Pawel , Barnard David , Frank Joachim 
Published: February 2005

AbstractThe three‐dimensional organization of the internal compartments of conventionally fixed and embedded rat‐liver mitochondria has been determined by tomographic reconstruction from tilt‐series images collected on the Albany high‐voltage electron microscope. The results indicate that the inner membranes of these organelles are predominantly tubular in the orthodox (expanded matrix) conformation, as previously suggested by scanning electron microscopy. In the condensed (contracted matrix) conformation, the intracristal space opens up into large irregularly shaped compartments which are connected to each other and to the external (intermembrane) space by tubes with approximately the same diameter (20 nm) as those observed in the orthodox state. These results raise several questions, in particular about the nature of the structural transitions that occur in the cristae during matrix expansion and contraction, and about the influence of inner‐membrane shape on the diffusion of ions and metabolites between the intracristal and intermembrane compartments. © 1994 Wiley‐Liss, Inc.
Allografts of CNS tissue possess a blood‐brain barrier: III. Neuropathological, methodological, and immunological considerations
Authors: Broadwell Richard D. , Baker Belinda J. , Ebert Paul S. , Hickey William F. 
Published: February 2005

AbstractDevelopment of a blood‐brain barrier (BBB) within mammalian CNS grafts, placed either intracerebrally or peripherally, has been controversial. Published data from this laboratory have emphasized the presence or the absence of a BBB within solid mammalian tissue or cell suspension grafts is determined intrinsically by the graft and not by the surrounding host parenchyma (e.g., brain, kidney, testis, etc.). Nevertheless, correctly interpreting whether or not a BBB exists within brain grafts is manifested by methodologies employed to answer the question and by ensuing neuropathological and immunological consequences of intracerebral grafting. The present study addresses these issues and suggests misinterpretation for the absence of a BBB in brain grafts can be attributed to: (1) rupture of interendothelial tight junctional complexes in vessels of CNS grafts fixed by perfusion of the host; (2) damage to host vessels and BBB during the intracerebral grafting procedure; (3) graft placement in proximity to inherently permeable vessels (e.g., CNS sites lying outside the BBB) supplying the subarachnoid space/pial surface and circumventricular organs such as the median eminence, area postrema, and choroid plexus; and (4) graft rejection associated with antigen presenting cells and the host immune response. The latter is prevalent in xenogeneic grafts and exists in allogeneic grafts with donor‐host mismatch in the major and/or minor histocompatibility complex. CNS grafts between non‐immunosuppressed outbred donor and host rats of the same strain (e.g., Sprague Dawley or Wistar rats) can be rejected by the host; these grafts exhibit populations of immuonohistochemically identifiable major histopatibility complex class I+ and class II+ cells (microglia, macrophages, etc.) and CD4+ T‐helper and CD8+ T‐cytotoxic lymphocytes. PC12 cell suspension grafts placed within the CNS of non‐immunosuppressed Sprague Dawley rats are rejected similarly. Donor cells from solid CNS grafts placed intracerebrally and stained immunohistochemically for donor major histocompatibility complex (MHC) class I expression are identified within the host spleen and lymph nodes; these donor MHC expressing cells may initiate the host immune response subsequent to the cells entering the general circulation through host cerebral vessels damaged during graft placement. Rapid healing of damaged cerebral vessels is stimulated with exogenously applied basic fibroblast growth factor, which may prove helpful in reducing the potential entry of donor cells to the host circulation. These results have implication clinically for the intracerebral grafting of human fetal CNS cell suspensions. © 1994 Wiley‐Liss, Inc.