bluuebunny/crossref_metadata_2025_split huggingface dataset:
Origin and migratory pathways of the eleven epithelial cell types present in the body of the mouse stomach
Authors: Karam Sherif , Leblond Charles Philippe 
Published: February 2005

AbstractThe secretions of the mammalian stomach are produced by cells present in invaginations of the epithelium, which in the mouse are straight tubules referred to as “zymogenic units.” These units comprise four regions, namely pit, isthmus, neck, and base, in which there are several cell lineages with different phenotypes and migratory pathways. In the isthmus, stem cells designated “undifferentiated granule‐free cells” undergo division so as to maintain their own number and produce several differently oriented progenitors: (1) “Pre‐pit cell precursors” are characterized by prosecretory Golgi vesicles with a uniform, fine particulate content. They give rise to “pre‐pit cells” defined by the presence of few dense mucous granules. These cells migrate outward from the isthmus to the pit, where they become the dense granule‐rich “pit cells” which populate the pit region and migrate to the gastric surface where they are lost. (2) “Pre‐neck cell precursors” are identified by prosecretory Golgi vesicles containing an irregular dense center and a light rim. They give rise to “pre‐neck cells” defined by a few mucous secretory granules with a clear‐cut core. These cells migrate inward from the isthmus to the neck where they become “neck cells,” which contain many such granules. Even though neck cells are mature mucus‐producers, they are not end cells. As they enter the base region, they become “prezymogenic cells” whose phenotype gradually changes from mucous to serous. These cells eventually lose the ability to produce mucus and thus become the typical zymogenic cells that populate the base region. (3) “Pre‐parietal cells” are classified into three variants, which probably come from three different sources, that is, pre‐pit cell precursors, pre‐neck precursors, and the undifferentiated granule‐free cells themselves. The preparietal cells mature into parietal cells which migrate either outward to the pit or inward to the neck and base. As a result, parietal cells are scattered in the four regions of the unit. (4) Precursors of “entero‐endocrine” and “caveolated” cells give rise in the isthmus to these cells, which may also migrate outward or inward. © 1995 Wiley‐Liss, Inc.
Development and application of a dry ultramicrotomy technique for the preparation of galvanneal sheet coatings
Authors: Barreto Marie Paule , Veillette René , L'espérance Gilles 
Published: February 2005

AbstractThe formability of galvanneal steel sheets used in the automotive industry is influenced by the presence and distribution of brittle and difficult to distinguish Zn‐Fe intermetallics in the coating. Characterization of these intermetallics requires a high spatial resolution technique such as analytical transmission electron microscopy (ATEM). Sample preparation by ion milling is impossible due to iron redeposition, and traditional ultramicrotomy using water affects the coating chemistry. A technique based on dry ultramicrotomy has therefore been developed.To optimize the technique, different parameters (knife angle, cutting medium, thickness setting on the ultramicrotome, cutting speed) have been investigated for the preparation of galvanneal coatings and pure Al sections. Results show that dry cutting does not affect the coating chemistry but shortens the life of the knife. Knife quality (cleanliness, sharpness and absence of defects) is a major factor to obtain good dry sections. The best results for the more ductile pure Al are obtained with a 35° knife whilst for the harder galvanneal coating it is recommended to use a 55° knife. These results suggest that the sectioning mechanism for the harder material involves more a cleavage‐fracture mechanism whilst a greater amount of shear is involved when sectioning relatively ductile Al. The optimum parameters for sectioning galvanneal coatings are established and results obtained by parallel electron energy loss spectrum imaging and energy dispersive X‐ray spectrometry in the TEM are given. This study shows that with a good control of all the sectioning parameters it is possible to obtain good sections repeatedly and rapidly. © 1995 Wiley‐Liss, Inc.
Ultramicrotomy of industrial alumina
Authors: Antonovsky A. 
Published: February 2005

AbstractIndustrial materials, such as alumina, often pose difficulties in their preparation for TEM examination. Composite and particulate materials are particularly difficult to prepare using conventional thinning techniques, i.e., ion beam and chemical jet thinning. Ultramicrotomy (UM) can be used to produce TEM specimens with a uniform thickness and an unaltered composition.Some crystalline materials, i.e., alumina hydrate, were difficult to section due to conflict between the cutting direction and cleavage planes. Sectioning was successful when these two directions were mutually parallel or perpendicular. At other orientations shattering occurred. Microcrystalline particulate materials, i.e., calcined alumina, were sectioned successfully in particles < 70 μm in diameter.The phases found in industrial alumina particles were gamma, delta, theta, and alpha alumina. Gamma alumina consisted of fine‐grained, equiaxed crystallites. The selected area electron diffraction (SAED) patterns indicated poor crystallinity with a distinct hexagonal texture. Delta and theta alumina appeared as an undifferentiated intermediary microstructure of elongated grains. The SAED patterns indicated poor crystallinity, but without a distinct texture. Alpha alumina was found to be a coarse‐grained crystalline phase with high diffraction contrast. SAED patterns consisted of fine, randomly oriented spots.Considerable variation was observed in the distribution of phases. In some specimens, discrete particles of gamma and alpha predominated. In others, particles were a mixture of phases repre‐sentative of the bulk composition. To characterise these samples, TEM of numerous whole particles was required. Ultramicrotomy was the only preparation technique capable of producing such samples. © 1995 Wiley‐Liss, Inc.
Ultramicrotomy of diamond films for tem cross‐section analysis
Authors: Swab P. 
Published: February 2005

AbstractUltramicrotomy has been used to prepare TEM cross‐sections of typical hard dielectric, semiconductor, and metal coatings, providing a critical capability in the study of structure‐property relationships of thin films. Ultramicrotomy of thin film coatings requires meticulous attention to technique and handling. The sample to be microtomed must be very small, well bonded to the epoxy embedding medium, and precisely oriented. In this article we report the ability to microtome TEM cross‐sections of diamond and cubic boron‐nitride (cBN) coatings. © 1995 Wiley‐Liss, Inc.
Microscopy of the gap junction: A historical perspective
Authors: Severs Nicholas J. 
Published: February 2005

AbstractGap junctions were discovered more than three decades ago, and since this time, enormous strides have been made in understanding their structure and function. This article summarises the part played by microscopy, within the context of multidisciplinary research, in the historical development of our knowledge of the gap junction. © 1995 Wiley‐Liss, Inc.
Differential connexin distribution accommodates cardiac function in different species
Authors: van Kempen Marjan J. A. , Velde Ingrid Ten , Wessels Andy , Oosthoek Petra W. , Gros Daniel , Jongsma Habo J. , Moorman Antoon F. M. , Lamers Wouter H. 
Published: February 2005

AbstractUsing immunohistochemical staining, the distribution of connexin40 (Cx40) and connexin43 (Cx43) was studied in rat, guinea pig, porcine, bovine and human hearts. These species display differences in the degree of morphological differentiation of the conduction system. This study was performed in the anticipation that comparison of the distributions of Cx40 and Cx43 in young and adult specimens may provide clues as to the physiological role of connexins in the heart. To a large extent, the distribution patterns of Cx40 and Cx43 are comparable between species. In neonates and adults, Cx43 was immunolocalized throughout the working myocardium, but in the conduction system Cx43 was detected only after birth. Cx40 was found to appear slightly earlier in development than Cx43 and to disappear when levels of Cx43 became more abundant. This time course was seen in working myocardium and in the ventricular conduction system. Together these data suggest that expression of Cx40 induces or facilitates expression of Cx43, while abundant expression of Cx43 in turn leads to suppression of Cx40 expression. The exceptions to this may represent blocks in this potential regulatory sequence. A second conclusion is that Cx40 and Cx43 containing gap junctions appear in the ventricular conduction system from distal to proximal and only after birth. This indicates that terminal differentiation of the conduction system occurs unexpectedly late in development. © 1995 Wiley‐Liss, Inc.
Elaboration of an oviductin by the oviductal epithelium in relation to embryo development as visualized by immunocytochemistry
Authors: Kan Frederick W. K. , Roux Emmanuelle 
Published: February 2005

AbstractThe hamster oviduct secretes a high molecular weight antigen that belongs to the family of glycoproteins known as oviductins. In the present study, using immuno‐electron microscopy, we examined the location of this hamster oviductin‐1 (Hm Ov‐1) in hamster oviductal oocytes and early embryos up to the blastocyst stage. The immunoreactive pattern of Hm Ov‐1 changes markedly during the embryo development. In oviductal oocytes prior to fertilization, Hm Ov‐1 was associated exclusively with the zona pellucida. Following fertilization, immunolabeling was detected in the perivitelline space and over the plasma membrane of 2‐cell, 4‐cell, and 8‐cell embryos as well as young blastocysts. The change of the immunoreactive pattern was accompanied by the formation of an abundant number of coated pits, endocytic vesicles, multivesicular bodies, and lysosomal‐like structures which were strongly labeled by gold particles. These immunogold‐labeled cytoplasmic organelles characteristic of the endosomal‐lysosomal apparatus were particularly evident in 2‐cell, 4‐cell, and 8‐cell embryos and showed a decrease in number in the blastocysts. The close resemblence between the labeled flocculent material detected in the perivitelline space and that found in the zona matrix of early embryos and blastocysts suggested that the Hm Ov‐1‐associated electron‐dense, flocculent material in the perivitelline space originated from the zona pellucida and was later endocytosed by the blastomeres through coated pits and endocytic vesicles. The detection of Hm Ov‐1 in numerous multivesicular bodies and lysosomal structures indicated that the oviductin is eventually degraded. Although the exact functional role of Hm Ov‐1 is not known, the presence of a copious amount of Hm Ov‐1 in early hamster embryos may be ascribed to a special relationship between this particular oviductin and embryo development. © 1995 Wiley‐Liss, Inc.
Bovine oviductal epithelial cells (boec) and oviducts: I. For embryo culture. Ii. Using sem for studying interactions with spermatozoa
Authors: Suzuki Hiroyuki , Foote Robert H. 
Published: February 2005

AbstractThe oviduct (uterine tube) plays a major role in reproduction. It is a dynamic organ which selectively permits a few sperm to undergo capacitation and reach the oocyte which has continued to undergo maturation following ovulation. Then following fertilization the embryo undergoes cleavage before arriving in the uterus. Extensive information has become available from in vitro studies on oocytes as well as spermatozoal interactions with oviductal cells. Bovine oviduct epithelial cell (BOEC) monolayers with simple media provide an environment in which zygotes can be cultured to blastocysts in 6 days with cell numbers essentially equivalent to blastocysts grown totally in the donor animal. These yield normal pregnancy rates upon transfer. The simple protein‐free media currently under test hold promise for elucidating specific requirements of the preimplantation embryo and these defined conditions facilitate many related studies on in vitro fertilization and genetic engineering of embryos.The second part of this paper is an extensive study on the interaction of fresh and frozen‐thawed bull spermatozoa with BOEC and segments of intact oviducts as viewed by SEM. Both types of oviductal cells were incubated at 39°C for 0, 3, 6, and 9 hours, using material obtained from periovulatory cows. Sperm attached immediately to both types of epithelium and reached a peak at 3 hours. They were found primarily in the furrows of the intact oviducts. Secretory droplets appeared rapidly on the anterior portion of the sperm head and acrosomal changes were evident in 3 hours, similar to those reported in vivo. Changes were more rapid with frozen‐thawed sperm. © 1995 Wiley‐Liss, Inc.
Functions of proteins secreted by oviduct epithelial cells
Authors: Gandolfi Fulvio 
Published: February 2005

AbstractStudies on embryonic development in vitro as well as observations in vivo, suggested that two aspects of oviduct physiology are important for early development. On one side has to be considered the oviduct “environment”: temperature, pH, osmotic pressure, nutrients, oxygen tension, free radical scavengers, etc. On the other, the oviduct “active components”: stimulatory and/or regulatory molecules, supposed to finely regulate the fertilisation process and the first differentiative steps.While the physical environment of the oviduct has been under investigation for some decades, studies on oviduct‐specific molecules and their functions have only been developed much more recently. The amount of information on this topic, however, has rapidly reached the size that demands a summary.In this review the descriptive literature on oviduct specific proteins will be examined as a basis for illustrating the possible functions of these molecules. In particular their role in fertilisation and early embryonic cleavages will be analysed in some details. Finally a section is devoted to the presence and physiological significance of growth factors in oviduct fluid. © 1995 Wiley‐Liss, Inc.
Quantitative and three‐dimensional aspects of the rat parathyroid gland in normo‐, hypo‐, and hypercalcemia
Authors: Wernerson Annika , Svensson Olle , Reinholt Finn P. 
Published: February 2005

AbstractThe ultrastructure of the rat parathyroid has been under study for more than 35 years, but controversies still exist, especially regarding structure‐function relationships. The present review focuses on recent morphological parathyroid research on rats under normal conditions and in various states of disturbed calcium metabolism. To facilitate discussions on functional aspects, current biochemical data, particularly those dealing with the regulation of parathyroid hormone synthesis and release, are also considered. Our results from quantitative studies and from investigations employing serial sectioning form the basis for the discussions. A central issue is whether the parathyroid secretory cells undergo secretory cycles. Prompted by results obtained from improved fixation procedures and serial sectioning, we question the basis for the theory of secretory cycles. Since the rat parathyroid secretory cell is polar, a single section is not an appropriate sample for estimating functional activity and for comparing the structure and distribution of intracellular components of adjacent cells. The heterogeneity in ultrastructural appearance of intracellular vesicles calls for the use of specific markers in relating the structure of the vesicular compartment to intracellular processing of hormone. The importance of unbiased quantitative techniques is illustrated in discussions on cell number and size for estimating the response of the parathyroid gland to different functional states or disorders demanding changes in secretion of parathyroid hormone, e.g., hyper‐ and hypocalcemia. © 1995 Wiley‐Liss, Inc.
Human lung volume, alveolar surface area, and capillary length
Authors: Wiebe Britt Marie , Laursen Henning 
Published: February 2005

AbstractWe compare the effectiveness of morphometric methods for extimating lung parameters. Various stereological methods are applied on human lungs and described in detail. The lung volume was estimated by Cavalieri's principle and by fluid displacement. But methods are reliable, but Cavalieri's principle is superior when systematic sections are needed or when volumes of parts of the lung are wanted. Point counting demonstrated that 87.5% of the lung is parenchyma, 5.4% is vessel volume, and 7.1% is bronchia volume. Alveolar surface was estimated on vertical and isotropic uniform random tissue (IUR) sections. The capillary length and length density was estimated on projected images of vertical slices (Gokhale method) and on IUR sections. Only minute differences were found whether IUR sections or vertical sections were used. Of the total variation, approximately 2% was due to the stereological variation and approximately 98% was due to the biological variation on IUR sections and vertical sections. Estimates for volumes, surfaces, and lengths coming from model‐based and design‐based methods gave similar results for human lungs. In our hands, the design‐based methods were easier to use and required less time. However, only the design‐based methods offer the guarantee of an unbiased estimate. © 1995 Wiley‐Liss, Inc.
Dysmyelination in class I MHC transgenic mice
Authors: Turnley Ann M. , Morahan Grant. 
Published: February 2005

AbstractWhy is it that oligodendrocytes do not normally express major histocompatibility complex (MHC) molecules? To examine the effect of aberrant MHC expression in oligodendrocytes, transgenic mice have been produced which expressed the class I MHC gene, H‐2Kb, under direction of the MBP promoter [Turnley et al. (1991b) Nature, 353:566‐569; Yoshioka et al. (1991) Mol. Cell. Biol., 11:5479‐5486]. A proportion of these mice exhibited a shivering phenotype, with tonic seizures and early death. Oligodendrocyte function and viability was shown to be affected, resulting in severe dysmyelination of the CNS. Is this phenomenon of cell damage due to aberrant expression of MHC molecules restricted to oligodendrocytes, and could other, non‐MHC molecules, when aberrantly expressed, result in similar cell damage? This paper discusses these questions and examines possible mechanisms for the oligodendrocyte damage and hypomyelination observed in these transgenic mice. Finally, the implications of aberrant MHC expression in oligodendrocytes for demyelinating diseases such as multiple sclerosis are discussed. © 1995 Wiley‐Liss, Inc.
Reconstruction of the glia limitans by sub‐arachnoid transplantation of astrocyte‐enriched cultures
Authors: Franklin R. J. M. , Blakemore W. F. 
Published: February 2005

AbstractLesions in CNS white matter involving loss of glial cells with concurrent destruction of the glia limitans lead to widespread remyelination of CNS axons by Schwann cells. Previous studies have demonstrated that this situation can be changed by transplanting cultured CNS glial cells into lesions early on in the repair process. In this study we have transplanted cultured astrocytes into the sub‐arachnoid space above such a lesion in order to (1) influence the normal repair process by transplant‐assisted reconstruction of the glia limitans, and (2) explore the potential of a minimally invasive route for introducing cells to white matter lesions. In some cases, it proved possible to influence normal repair by transplanting cells via the sub‐arachnoid route, although the results were inconsistent. However, the experiment permitted observations to be made on the migration of transplanted astrocytes across the surface of and within the spinal cord. © 1995 Wiley‐Liss, Inc.
Theory and practice of stereological techniques applied to the estimation of cell number and nuclear volume in the testis
Authors: Wreford Nigel G. 
Published: February 2005

AbstractThe historical background to contemporary approaches to the estimation of cell/ nuclear number and volume in the testes is reviewed. The limitations of older geometric model‐based approaches to the estimation of cell/nuclear number are discussed, and the need for absolute estimates of cell number rather than ratio estimates is examined. The physical and optical disector approaches to the direct estimation of numerical density and, hence, absolute cell number are presented together with data illustrating their operational efficiency in the testis. New approaches to the direct estimation of nuclear/cell volume, using the point‐sampled intercept family of methods, are presented and illustrated, using the example of the Sertoli cell nucleus. The use of both classical transverse and the newer vertical section approaches is explored. Estimation of Sertoli cell/nuclear volume in the volume (point‐sampled intercept procedure) and number (nucleator and rotator methods) distributions on both conventional transverse and vertical sections is discussed. The use of transverse sections of the testis is shown to produce a consistent bias in the estimation of Sertoli cell nuclear volume in 120‐day‐old animals, with all the estimators. Comparison of the Sertoli cell nuclear volume (measured on vertical sections) in the volume and number‐weighted distribution suggests a coefficient of variation of volume in the number distribution of 0.4–0.5, suggesting either a random or stage‐dependent variation in Sertoli cell nuclear size which requires further exploration. © 1995 Wiley‐Liss, Inc.
Integumentary changes during moulting of arthropods with special reference to the subcuticle and ecdysial membrane
Authors: Taylor Ronald L. , Glenn Richards A. 
Published: February 2005

AbstractAt or shortly prior to the separation of the cuticle and the epidermis a cuticular layer appears to be added to the inner surface of the old cuticle. The term interzone cuticle is applied to this layer. The interzone cuticle appears to give rise to the ecdysial membrane.Ecdysial membranes are characterized by the fact that they (1) vary in position with respect to the moulting fluid and old cuticle, (2) are generally quite thin, transparent, delicate membranes, (3) contain chitin, (4) vary in their resistance to the action of the moulting fluid, and (5) generally have the same stainng properties as the subcuticle, due primarily to the presence of a mucous material present in the subcuticle which becomes attached to the inner surface of the ecdysial membrane and which is believed to function as a lubricant at ecdysis.The ecdysial membrane and subcuticle are structurally quite different when examined under the electron microscope.No particular evolutionary significance can be ascribed to the existence of an ecdysial membrane — such membranes being found all the way from the primitive Collembola to the advanced Hymenoptera. Any possible function(s) of the ecdysial membrane has yet to be discovered. Various functions are suggested for the subcuticle, all of which are consistent with its reactions to various histochemical reagents.Additional observations were made and discussed concerning (1) the reactions of various portions of the cuticle at various stages to the PAS test, (2) the staining reactions of cuticle undergoing enzymatic degradation by the moulting fluid, and (3) the distinct staining reactions of the intersegmental membranes and basement membranes.