bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neonatal development of the diaphragm of the horse, Equus caballus
Authors: Cobb Matthew A. , Schutt William A. , Petrie Jacquelyn L. , Hermanson John W. 
Published: February 2005

AbstractThe diaphragm of neonatal horses is significantly different from the diaphragm of adult horses in terms of histochemical fiber type composition, myosin heavy chain isoform, and native myosin isoform composition. There is a significant increase in the percentage of type I fibers present in the diaphragm with increasing age from birth through about seven months postnatal age. A possible lack of postural tone in the hiatal region of the neonatal diaphragm is suggested to account for increased incidence of vomiting or aspiration pneumonia in younger horses. The isoform data lead to rejection of the hypothesis that the diaphragm of the horse should, as an ungulate, be relatively precocial in its rate of maturation relative to other non‐ungulate mammals that have been studied. © 1994 Wiley‐Liss, Inc.
Translocation of enamel proteins from inner enamel epithelia to odontoblasts during mouse tooth development
Authors: Nakamura Masanori , Bringas Pablo , Nanci Antonio , Zeichner‐David Margarita , Ashdown Brian , Slavkin Harold C. 
Published: February 2005

AbstractThe developmental problem of how dental epithelia and/or dental papilla ectomesenchyme induce and/or up‐ or down‐regulate tooth formation are as yet unresolved issues. We have desinged studies to map the synthesis and fate pathways of secreted amelogenin proteins from Kallenbach differentiation zones II–IV during in vivo and in vitro mouse mandibular first molar tooth development (M1). Tooth organs from cap, bell, and crown stages were processed for reverse transcriptase/polymerase chain reaction (RT‐PCR) and high resolution Protein A immunocytochemistry using anti‐amelogenin and anti‐peptide antibodies. Cap stage M1 were cultured for periods ranging from 10–21 days in vitro using either serumless, or 15% fetal calf sera‐supplemented, chemically‐defined medium. Amelogenin transcripts are expressed in the mouse embryonic molar from E15 through early postnatal development. Amelogenin antigens were first detected in Kallenbach's differentiation zone II. Amelogenin proteins secreted from preameloblasts were identified along cell processes and cell surfaces of odontoblasts adjacent to forming mantle dentine extracellular matrix (ECM) prior to biomineralization. Amelogenin proteins were restricted to forming endocytotic vesicles, clathrin‐coated vesicles, and lysozomes within odontoblasts. At later stages (e.g. 2 days postnatal development), enamel proteins were not identified in odontoblasts or predentine matrix following mineralization. Comparable observations for stages of development were noted for in vitro cultured tooth explants. Preameloblasts synthesize and secrete amelogenin proteins which bind to odontoblast cell surfaces possibly through the process of receptor‐mediated endocytosis. We conclude that amelogenin proteins secreted from preameloblasts, prior to the initiation of biomineralization, were translocated to odontoblasts to serve as yet unknown biological functions. © 1994 Wiley‐Liss, Inc.
Ultrastructural studies and immunolocalization of enamel proteins in rodent secretory stage ameloblasts processed by various cryofixation methods
Authors: Nanci A. , Kawaguchi H. , Kogaya Y. 
Published: February 2005

AbstractBackground: Cryofixation rapidly immobilizes cell and tissue components in their native state, thereby resulting in an ultrastructural preservation very close to the living situation. We have applied this approach to examine the morphology of secretory stage ameloblasts and the distribution of enamel proteins in these cells.Methods: Molar and incisor tooth germs from newborn mice and/or rats were quickly dissected and divided into segments. The segments were then rapidly frozen using slam, plunge or pressure freezing, freeze‐substituted and embedded in Epon. In addition, incisors from older rats were chemically fixed by vascular perfusion and also dehydrated by freeze‐substitution.Results: Well‐preserved ameloblasts were obtained with all four tissue processing methods. However, slam freezing often showed mechanical damage to the ameloblasts, particularly at the level of the distal portion of Tomes' processes which appeared severed or distorted. Plunging into liquid nitrogen‐cooled liquid propane resulted in comparatively less tissue distortion. High pressure freezing gave a relatively higher yield of well‐preserved specimens, although displacement of organelles in ameloblasts was sometimes observed, probably resulting from hydrostatic pressure. Minimal ice crystal and mechanical damage was observed in chemically fixed tooth samples processed by freeze‐substitution since such specimens are cryoprotected and their examination is not restricted to a surface layer. With all of the above cryopreparation methods, the ultrastructure of well preserved ameloblasts was, in general, similar to that obtained following conventional chemical fixation, and immunocytochemistry with an anti‐amelogenin antibody indicated no profound differences in the distribution of enamel proteins.Conclusions: These results indicate that, despite some limitations, it is possible to adequately cryofix tooth organs while preserving the architecture of ameloblasts and permitting immunolocalization of enamel proteins. Furthermore, they confirm the general morphology of secretory stage ameloblasts as currently derived from conventional chemical tissue processing. © 1994 Wiley‐Liss, Inc.
Organization of tracheal epithelium in the cartilaginous portion of adult rabbit and its persistence in organ culture
Authors: Johnson Russell A. , Stauber Ziva , Robert Hilfer S. , Kelsen Steven G. 
Published: February 2005

AbstractBackground: The rabbit trachea provides a model system to test the physiological responses of the airways to various agents. Since three‐dimensional organization may affect responses of an organ, an organ culture model was established in serum free medium.Methods: Tracheas were fixed in situ, at steps in the preparation of organ cultures, and after one day to three weeks in organ culture. Samples were examined by light microscopy and scanning and transmission electron microscopy for surface morphology, distribution of cell types, and characteristics of the epithelial cell layer.Results: The normal tracheal mucosa was discovered to consist of extensive circumferential folds in the cartilaginous portion, which were enhanced upon isolation of the trachea from the animal. The folds consisted principally of differences in epithelial cell height rather than folding of the lamina propria. Enhancement of folding upon removal of the trachea coincided with increased secretion by Clara and possibly mucous cells. In organ culture, epithelial cell height initially increased, producing tall folds and cell types were retained in normal proportions. After prolonged culture, cilia were lost but glandular secretion continued.Conclusions: Changes in the arrangement of basal cells and secretory activity in isolated trachea and in culture may give insight into the functional significance of the epithelial folds. © 1994 Wiley‐Liss, Inc.
Ultrastructure and development of a thick basement membrane‐like layer in the anchoring villi of macaque placentas
Authors: King Barry F. , Blankenship Thomas N. 
Published: February 2005

AbstractBackground: Anchoring villi and cytotrophoblastic cell columns are important structural components involved in placental morphogenesis. We have previously described the presence of an unusual basement membrane‐like layer (BMLL) that separates these placental compartments. The purpose of the present study was to identify developmental changes in the ultrastructure of the BMLL and to assess its changes in extracellular matrix composition over the course of gestation.Methods: Conventional techniques were used to examine macaque placental tissue by transmission electron microscopy. Standard immunoperoxidase methods were used to identify type IV collagen, laminin and fibronectin in paraffin sections.Results: Until day 35 of gestation the BMLL was 70–100 nm thick and appeared similar to basement membranes seen in other regions of the villus, although it usually lacked a lamina lucida along the surface adjacent to the cytotrophoblast cells. Immunohistochemistry revealed the presence of laminin and type IV collagen in the BMLL. By 53 days of gestation the BMLL had hypertrophied at the junction of the anchoring villus and cell column, measuring 2,000–5,000 nm in thickness. The BMLL retained immunoreactivity for laminin and type IV collagen. Ultrastructural examination revealed the presence of a new component in the form of 10 nm microfibrils. By 89 days of gestation the BMLL was not reactive for laminin or type IV collagen but otherwise maintained the structural organization seen at 53 days. No additional changes were observed in the BMLL during late pregnancy.Conclusions: The BMLL is a distinct extracellular matrix region that separates the distal aspect of the anchoring villus from the proximal portion of the cell columns. Evidence indicates that adjacent cytotrophoblast plays a prominent role in the production of the BMLL. The BMLL may serve to organize this complex tissue by separating fetal mesenchyme from cytotrophoblast cells that are proliferating, differentiating, and migrating. Modifications to the composition of the BMLL may indicate changes in the role this matrix plays in the development of the placenta. © 1994 Wiley‐Liss, Inc.
Extractions reveal specific argentophilic proteins in rat and bull sperm heads
Authors: Yagi Ahmed , Paranko Jorma 
Published: February 2005

AbstractBackground: Silver‐stainability (argentophilia) of cytoplastmic structures occurring in spermatids have been localized into the organizing perinuclear theca, but the biochemical nature and structural associations of these proteins with the cytoskeletal and membranous elements are unresolved and, therefore, were the aim of the present study.Methods: Light and electron microscopic analysis of the silver‐stainability in the rat spermatids and spermatozoa was carried out in the intact testis tissue and epididymal spermatozoa and after their chemical and mechanical extraction. Correlation of argentophilia with specific proteins of rat and bovine spermatids and spermatozoa was investigated using a recently developed technique for silver nitrate staining of proteins on nitro‐cellulose.Results: Sequential formation of the silver‐stainable domains seemed to proceed from the argentophilic acrosomal ring. Various extractions indicated that argentophilia in the spermatids and spermatozoa was mainly associated with the perinuclear theca and to some extent to the plasma membrane. Hyamine‐soluble extract from spermatozoa of rat and bull revealed only a single argentophilic protein of 130 kDa. Hyamine and SDS‐soluble extracts of rat testis tissue contained an additional group of argentophilic polypeptides of lower molecular weight (115, 94, 36, 23, and 21 kDa).Conclusions: Reduction in the number of argentophilic proteins appears to be involved in a series of changes in the cyto‐architecture of developing spermatids. Tentative cytoskeletal nature of argentophilic proteins remains to be identified. Nevertheless, they may have important physical relations with the higher‐order organization of the sperm head cytoskeleton and overlying membranes. © 1994 Wiley‐Liss, Inc.
Neuroepithelial bodies in the lung of Basiliscus vittatus (Reptilia, Iguanidae)
Authors: Steen Peter van Den , van Lommel Alfons , Lauweryns Joseph M. 
Published: February 2005

AbstractBackground: Neuro‐epithelial bodies (NEB) are corpuscles of currently equivocal function which are present in the lungs of vertebrates. Comparative studies may help to elucidate their role.Methods: The NEB of Basiliscus vittatus (Reptilia, Iguanidae), a terrestrial lower vertebrate able to dive, are for the first time examined by electron microscopy, immunocytochemistry, and for argyrophilia.Results: Most NEB contain both immunoreactive calcitonin and serotonin but are not labelled with argyrophilia or immunocytochemistry against calcitonin gene‐related peptide (CGRP), protein gene product 9.5 (PGP 9.5), or the Leu‐7 epitope (Leu‐7). Therefore, in NEB of this species, the transcription of the calcitonin/CGRP gene exclusively favors the expression of calcitonin and this is in contrast to the intrapulmonary small neurons. Also, a physiologic difference is expected in the metabolism of ubiquitin in NEB of B. vittatus vs. mammalian NEB and neurons. In addition, the NEB cells are always covered by at least a thin cytoplasmic extension of a neighbouring cell, indicating that luminal contact is not required. Stronger still, it appears that in some lower vertebrates contact to the airspace is avoided. Finally, we provide ultrastructural evidence for the basket‐like innervation of NEB in some reptiles. This way of innervation possibly represents an evolutionarily different concept for interaction between NEB corpuscular cells and nerve fibers.Conclusions: Beyond the confirmation that morphology, content of biologically active substances such as serotonin and calcitonin, and innervation are evolutionary well preserved features of NEB, the results reveal some intriguing features of B. vittatus NEB: strict separation of calcitonin and CGRP, reduced need for the de‐ubiquitinating enzyme PGP 9.5, lack of luminal contact, and the basket‐like innervation. The latter two properties possibly refer to a mechanoreceptor function of NEB in this species. © 1994 Wiley‐Liss, Inc.
Conjoined twin piglets with duplicated cranial and caudal axes
Authors: McManus Cheryl A. , Partlow Gary D. , Fisher Kenneth R. S. 
Published: February 2005

AbstractBackground: Twins with doubliong of the cranial and crudal poles, yet having a single thorax, are rare.Methods: One set of diprosopus, dipygus porcine conjoined twins was studied.Results: In addition to the conjoining anomaly, these twins also exhibited ambiguous internal reproductive features. The twins had two snouts, three eyes, a single thorax, and were duplicated from the umbilicus caudally. Radiography indicated a single vertebral column in the cervical region. The vertebral columns were separate caudally from this point. There was a total of six limbs—one pair of forelimbs and two pairs of hindlimbs. Many medial structures failed to develop in these twins. Medial cranial nerves V–XII were absent or displaced although apprarently normal laterally. The medial palates were present but shortened, whereas the medial mandibular rami had folded back on themselves rostrally to form a midline mass between the two chins. Each twin had only one lateral kidney and one lateral tests. Medial scrotal sacs were present but devoid of a testis. There was a midline, “uterine”‐like structure which crossed between the twins. However, histological analysis of this structure revealed it to be dysplastic testicular tissue.Conclusions: The relationship between the abnormal reproductive features in these twins and the conjoining is unclear. The anatomy of these twins, in addition to the literature reviewed, illustrates the internal anatomical heterogeneity of grossly similar conjoined twins. A review of the literature also suggests that conjoined twinning may be more common in swine than was previously suspected. © 1994 Wiley‐Liss, Inc.
Association of the cardiac neural crest with development of the coronary arteries in the chick embryo
Authors: Waldo Karen L. , Kumiski Donna H. , Kirby Margaret L. 
Published: February 2005

AbstractBackground: Chick coronary arteries orginate as penetrating channels from a subepithelial peritruncal ring into the wall of all three aortic coronary sinuses. Two of these capillaries develop a muscular wall and become the definitive coronary arteries. Since cardiac neural crest (CNC) contributes ectomesenchyme to the tunica media (TM) of the aortic arch vessels, we wished to learn if the CNC also contributes to the media of the coronary arteries and if CNC plays an inductive role in determining the site of aortic penetrations and influences which channels persist to hatching.Methods: Quail‐to‐chick chimeras were made by bilaterally removing the chick CNC and replacing it with quail CNC. The chimeras and unoperated controls were collected on embryonic days (ED) 7–18, fixed in Carnoy's fixative, serially sectioned, stained with Feulgen‐Rossenbeck stain, and analyzed. Several ED 18 controls and chimeras were also stained with Gomori's trichrome stain, or labeled with antineurofilament or antivascular smooth muscle alpha actin.Results: The TM of the coronary arteries and the aortic coronary sinuses did not consist of CNC cells. The media of the surviving coronary arteries was disrupted by clusters of CNC cells scattered in the wall of the base of the coronary artery on ED 14 and 18. Persisting coronary arteries were always associated with large neural crest‐derived parasympathetic ganglia near their origin. Branches from parasympathetic nerves entered the base of the coronary arteries where the clusters of neural crest cells were located. Quail cells were also associated with tiny vessels exiting the ostia of the coronary arteries and traveling in the outer aortic wall. Labeling with antibodies confirmed a disruption of the TM at the base of the coronary arteries, and showed innervated clusters of quail cells in the disrupted part of the TM.Conclusion: Although the TM of the coronary arteries and the aortic coronary sinuses contained no CNC cells, clusters of innervated quail cells disrupted the TM at the base of the coronary arteries. CNC does not appear to induce capillary penetration direclty; however, the exclusive association of CNC‐derived parasympathetic ganglia and nerves with persisting coronary arteries suggests that the presence of parasympathetic ganglia is essential to the survival of the definitive coronary arteries. CNC cells may also be associated with the development of the aortic vasa vasorum. © 1994 Wiley‐Liss, Inc.
Effects of distribution of muscle fiber length on active length‐force characteristics of rat gastrocnemius medialis
Authors: Ettema Gertjan J. C. , Huijing Peter A. 
Published: February 2005

AbstractBackground: The length‐force curve of mammalian skeletal muscle is often wider than expected on basis of the optimum length of the muscle fibers. Two important effects may explain this discrepancy: muscle pennation and distribution of fiber lengths in the muscle. In the present study of the effects of a Gaussian distribution of fiber lengths on muscle length‐force characteristics were investigated in rat gastrocnemius medialis.Methods: Fiber length‐force characteristics and parameter values of the Gaussian distribution were derived from literature data (Stephenson et al., 1989, J. Physiol., 410:351–366; Heslinga and Huijing, 1990, J. Morph. 206:119–132; Zuurbier and Huijing, 1993, J. Morphol., 218:167–180). Three different constructions of the distribution model were compared with experimental data. Pennation effects were incorporated in the model.Results: Two constructions gave reasonably good results: (1) the model with a fiber optimum distribution, in which fibers acted at the same absolute length at a given muscle length; (2) the model in which fiber optimum length was uniform but absolute length at a given muscle length was distributed.Conclusions: In rat gastrocnemius medialis, the magnitude of the effects of these distributions is similar to pennation effects. The current results help to explain the relative wide working range of skeletal muscles in human movement and the differences in specific muscle tension as affected by muscle type, species, and age. © 1994 Wiley‐Liss, Inc.
Middle‐ear development VI: Structural maturation of the rat conducting apparatus
Authors: Zimmer Wayne M. , Rosin Deborah F. , Saunders James C. 
Published: February 2005

AbstractBackground: The contribution of middle‐ear development to the overall development of hearing has not been explored in great detail. This presentation describes the maturation of conductive elements in the rat middle ear, and provides the basis on which future studies of middle‐ear functional development will follow.Methods: The middle‐ear apparatus was examined at nine different ages (between 1 and 80 days postpartum) in Long Evans rats. At each age elements of the conducting apparatus were observed with either light or scanning electron microscopy (SEM), and quantitative measurements were made from video enhanced photomicrographs. Tympanic membrane area and cone depth, the length of the malleus and incus arms, ossicular weight, stapes foot plate and oval window areas, and bulla volume were all measured. Development of the area and lever ratios were derived from these measurements. The data were fitted to exponential equations and the time in days required to reach 90% of the adult level determined.Results: The pars tensa achieved 90% of total area by 17 days. The oval window achieved the 90% criterion by 13 days, while the area ratio was within 10% of its adult size by 8 days. The ossicles took between 26 and 34 days, while bulla volume took 59 days to reach the 90% level.Conclusions: Middle‐ear growth was very orderly and systematic in the data reported. When maturation of the area ratio was considered against development of the endocochlear potential or the round window compound action potential, it was clear that the growth of this important aspect of the middle ear preceded the onset of cochlear function. © 1994 Wiley‐Liss, Inc.