bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of germ cells and sertoli cells in the postnatal rabbit testis
Authors: Gondos Bernard , Renston Richard H. , Conner Lucy A. 
Published: February 2005

AbstractSpermatogenesis begins in the rabbit at seven to eight weeks of age. During the preceding postnatal period, seminiferous tubules contain round to oval prespermatogonia arranged in pairs at the tubular periphery and elongated Sertoli cells lying perpendicular to the basal lamina. Prespermatogonia are distinguished from fetal gonocytes by their abundant cytoplasm and the presence of intercellular bridges. Preceding the onset of spermatogenesis, prespermatogonia undergo diminution in cell size and cytoplasmic condensation. At the same time there is marked nucleolar enlargement, with elaborate proliferation of the nucleolonema. By the end of the seventh week, characteristic type A and B spermatogonia are present. Spermatocytes are seen at the end of the eighth week. Spermatids appear in the twelfth week, coincident with tubular lumen formation. The duration of the initial spermatogenic cycle is similar to that in the adult. Sertoli cells are closely associated with adjacent germinal elements throughout the postnatal period. The Sertoli cell cytoplasm includes elongated mitochondria, abundant smooth endoplasmic reticulum and prominent Golgi complexes. Many of the cells contain phagocytized material, presumably derived from degenerating germ cells. The observations suggest possible mechanisms by which Sertoli cells support early germ cell maturation.
Pinocytosis by epithelium associated with lymphoid follicles in the bursa of fabricius, appendix, and Peyer's patches. An electron microscopic study
Authors: Bockman Dale E. , Cooper Max D. 
Published: February 2005

AbstractThe fine structure and micropinocytotic capabilities of epithelial cells closely associated with lymphoid follicles in the chicken bursa of Fabricius, rabbit appendix, and mouse Peyer's patch were compared. Epithelial cells capable of transporting ferritin and India ink tracers from the lumen were demonstrated in all three locations. Epithelial cells not associated with lymphoid follicles in the bursa and appendix did not express pinocytotic activity. Lymphoid cells were identified in bursal epithelium of chick embryos as early as the twelfth day of incubation. These lymphoid cells were smaller than typical bursal lymphocytes, had dense cytoplasm, numerous cytoplasmic projections, and prominent nucleoli. The small lymphoid cells were first demonstrable at a time in incubation during which lymphoid stem cells have been shown to migrate into the bursal epithelium. Lymphoid cells were seen earlier than the specialized follicle‐associated epithelium. It is concluded that specialized pinocytotic follicle‐associated epithelium does not induce initial migration of stem cells into areas along the intestinal tract, but that this transepithelial pinocytotic flow of intestinal contents after birth may provide a significant stimulus for attraction, proliferation and egression of lymphocytes.
Experimental manipulation of desmosome structure
Authors: Borysenko Joan Z. , Revel Jean Paul 
Published: February 2005

AbstractA systematic investigation of the effects of proteolytic enzymes, chelators and detergents on desmosomes originating in a variety of tissues was undertaken. Although junctions from different tissues are morphologically similar, we found great differences in their sensitivity to various reagents, indicating dissimilarities in biochemical composition.In general, desmosomes from stratified squamous and glandular epithelia were insensitive to ethylenediaminetetraacetic acid (EDTA), but readily dissociable with trypsin. Enzymatic digestion caused disruption of material within the junctional extracellular space, and dislocation of paired desmosomal plaques. In contrast, the extracellular components of desmosomes from simple columnar epithelia were usually EDTA‐sensitive but trypsin‐resistant. There were, however, exceptions to the general pattern. Desmosomes from rat pancreas were affected only by the detergent sodium desoxycholate (DOC). DOC also solubilized the intermediate dense line of desmosomes from the frog skin.We have divided desmosomes into two broad categories based upon the differential effects of these reagents. One group, sensitive to trypsin or DOC, may be functionally “stable” in maintaining cell‐to‐cell associations for long periods. Such junctions occur in stratified squamous and many glandular epithelia. Another group of desmosomes, affected by chelating agents, may be physiologically “labile” or plastic. These junctions, occurring in simple columnar epithelia such as the gut, may respond to physiological stimuli by opening or closing, thus allowing intercellular migration of cells and substances passing through the epithelial sheet.
Dynamic function of the human fibula
Authors: Weinert Carl R. , McMaster James H. , Ferguson Roger J. 
Published: February 2005

AbstractThere is general agreement that motion between the tibia and fibula is an important and necessary part of normal ankle function in man.We studied the function of the tibiofibular unit in healthy college athletes running barefooted. Movies and cine‐roentgenograms showed the fibula moving downward and laterally during the strike phase of gait. Fibular motion in this direction rather than upward, as suggested by cadaver studies, deepens the ankle mortice and stabilizes the joint when the ankle is dorsiflexed and load is the greatest. This motion also stretches the interosseous membrane and tibiofibular ligaments, converting compressive force in the ankle to tension in these structures.
The morphology of M. tensor veli palatini in the five‐month human fetus
Authors: Rood Stewart R. 
Published: February 2005

AbstractThe morphology of M. tensor veli palatini in the five‐month human fetus was studied using a light microscopic procedure. The muscle was found to be divided into two fairly distinct bundles. In cross‐section, the fibers of the more lateral bundle coursed in an inferior‐superior direction from the hard palate to the level of the cranial base. The fibers of the bundle lying just lateral to the Eustachian tube and medial to the previously identified bundle ran in a medial‐lateral direction between their attachment to the lateral membranous tubal wall and the fibroelastic tissue layer separating the two bundles. It is suggested that these observations may account in part for lateral movement of the lateral membranous wall without necessitating a hamular or velar insertion of the tensor palati.
The early differentiation of the testis and interstitial cells in the fetal pig, and its duplication in organ culture
Authors: Moon Young S. , Hardy Margaret H. 
Published: February 2005

AbstractThe unusual histogenesis of the fetal pig testis was examined as part of a study of its role in reproductive biology. Three types of interstitial cells were defined and their numbers estimated per unit area of testicular tissue in 6 μ‐serial sections. Statistical analysis of the percentage frequency of each cell type showed that the mature Leydig cells (C‐type) reached a peak at about 4.5 cm crown‐rump length (CRL) fetus and then fell to a low level, rising again sharply from 20 cm CRL until near birth. It was postulated that the first mature Leydig (C‐type) cells arose from mesenchymal (A‐type) cells which differentiated first into immature Leydig (B‐type) cells, and the process was repeated in the last part of fetal life.Mixtures of cock plasma, chicken embryo extract and balanced salt solution allowed maintenance and differentiation of whole fetal testes or testicular slices as organ cultures in Maximow slide assemblies for 6 to 14 days. Medium 199 with 10% bovine serum allowed maintenance and differentiation in some explants for at least six days. Indifferent gonads developed into recognizable testes or ovaries. Testes from 2.5, 3.0, and 3.5 cm CRL fetuses differentiated at a fairly normal rate, and some of their interstitial cells underwent the transformation postulated from the in vivo study. It was concluded that organ cultures from indifferent gonads and early testes provided living, functioning systems which could be used to test for androgenic activity with biological indicators.
Morphogenesis of the fetal membranes and placenta of the black bear, Ursus americanus (pallas)
Authors: Wimsatt William A. 
Published: February 2005

AbstractKnowledge of placentation in bears has been limited to analysis of a single shed placenta of the European brown bear. It was shown that the mature allantoic placenta is discoidal, endotheliochorial, provided with a circular marginal hematoma, and that the allantoic sac is large and permanent. The present study, based on a small series of conceptuses younger than any previously examined, provides new details concerning implantation and the morphogenesis of the fetal membranes, placenta and paraplacental organs. Implantation in the black bear is central and superficial; the orientation of the embryonic disc is antimesometrial. Amniogenesis and chorion formation are almost certainly accomplished by folding. The decidual reaction is minimal. As in other carnivores the yolk sac is prominent early, but progressively declines. A well‐developed choriovitelline placenta is formed early, but is eliminated before the limb bud stage. The bilaminar omphalopleure persists only slightly beyond the limb bud stage. The allantois, however, is extensive and permanent. Initially, the allantoic placenta is cup‐shaped but eventually flattens out to form the discoidal placenta. It is lobuliform and endotheliochorial, and probably a marked attenuation of the interhemal membrane occurs in later stages. The marginal hematoma, which is completed before the limb bud stage, is formed by enlargement and coalescence of separate extravasations, and apparently remains fully functional to term. Overall, morphogenetic sequences and relationships in bears more nearly resemble those of the dog than of other carnivores.
The origin, distribution and disappearance of surface cilia during embryonic development of Rana pipiens as revealed by scanning electron microscopy
Authors: Kessel R. G. , Beams H. W. , Shih C. Y. 
Published: February 2005

AbstractCilia begin to grow from the free surface of some ectodermal cells during the neural plate stage (stage 13). Ciliary growth is not closely synchronized between cells in the same embryo, but the number of ciliated cells increases greatly during neural fold development and further growth in length of pre‐existing cilia occurs. Ciliated cells are numerous and widely distributed over the surface of early tailbud stages. However, cilia do not develop on cells in the neural plate and inner sides of the neural fold, and only an occasional ciliated cell is observed on the surface of the paired suckers. The number of ciliated epidermal cells per embryo increases during tail growth (stages 18–22). Ciliated epidermal cells persist after hatching (stage 20), but regression of cilia can be detected in stage 24 larvae. By late stage 25, most of the cilia have disappeared and the morphological variations observed indicate that the process involves resorption of cilia. Non‐ciliated (secretory) ectodermal cells from the neurula onward to stage 25 synthesize granules which are released to provide a mucous‐like coat for the embryo and larva. The surface structure of both ciliated and non‐ciliated ectodermal cells is described in sections studied with the transmission electron microscope and compared to the surface architecture of both cell types observed with the scanning electron microscope.
Spermatogonial stem cells in the albino rat
Authors: Clermont Yves , Hermo Louis 
Published: February 2005

AbstractThe existence of two classes of spermatogonial stem cells in the rat testis, i.e., reserve type A0 spermatogonia and renewing, types A1‐A4 spermatogonia, postulated by Clermont and Bustos‐Obregon (′68), was reexamined in a quantitative analysis of type A spermatogonia in both whole mounts of tubules and in radioautographed sections of testes from animals killed at various times, up to 26 days, after one or multiple injections of 3H‐thymidine.The cell counts obtained from whole mounts of tubules revealed that the number of isolated type A0 cells per unit area of limiting membrane remained constant throughout the cycle of the seminiferous epithelium. Paired type A0 spermatogonia also remained unchanged in number per unit area of basement membrane from stage I to stage VIII of the cycle. The low mitotic index of type A0 spermatogonia (0.1%) indicated that these cells were not actively involved in the production of spermatogonia or spermatocytes during each cycle of the seminiferous epithelium and thus were considered as reserve stem cells.The type A1 spermatogonia, which are formed during stage I of the cycle, remained resting until stage IX, when they undertook a series of four successive divisions resulting in the production of new type A1 and Intermediate‐type spermatogonia. An analysis of the labeling indices of type A spermatogonia obtained from cell counts in radioautographed testicular sections after a single or multiple 3H‐thymidine injections indicated that the percentages of labeled type A cells corresponded to the percentages of type A1‐A4 at each stage, whereas the percentages of unlabeled type A cells corresponded to the percentages of type A0 spermatogonia obtained from counts of cells in whole mounts. This confirmed that type A0 cells were generally non‐proliferative throughout the cycle of the seminiferous epithelium while the type A1‐A4 spermatogonia underwent complete renewal during each cycle. The present results thus support the concept of the existence of two classes of spermatogonial stem cells in rats.
Direct quantitative estimation of Paneth and total cell populations in the jejunal glands of Lieberkühn
Authors: Malinin George I. 
Published: February 2005

AbstractDirect morphometric estimation of the number of intestinal crypts per 10 mm length of jejunum, the total number of cells per crypt, and the number of Paneth cells per crypt was performed using Zenker‐fixed, serially sectioned small intestines from adult BALB/c mice. The mean volume of a crypt cell was estimated to be in the order of 6.6 ± 0.1 × 10−4 mm3, while the total volume of all cells in a single crypt was 1.833 ± 0.02 × 10−1 mm3. The cell population per crypt was 278 ± 7 cells, of which 44 ± 10 were Paneth cells. It was estimated further that 265 ± 30 crypts per 10 mm length of jejunum contained 7.4 ± 0.1 × 104 cells, including 1.2 ± 0.24 × 103 Paneth cells. The volume of all crypt and Paneth cells per 10 mm length of jejunum was in the order of 49 ± 1.2 and 8 ± 1.8 mm3, respectively. The volume of the tunica muscularis and the surface area of the crypt's lumina were estimated to be 33.5 ± 2.2 mm3 and 118 ± 19 mm2, respectively.
Motor‐sensory cortex‐corticospinal system and developing locomotion and placing in rats
Authors: Hicks Samuel P. , D'Amato Constance J. 
Published: February 2005

AbstractNormal and abnormal development of movement in the rat were studied by investigating the growth and organization of the motor‐sensory cortexcorticospinal tract system (MSC‐CST) and the functional and morphologic effects of ablating the MSC or quadrants of it at different ages. Major growth of the MSC outflow, the CST, in the brain stem and rostral cord occurred in the second and third weeks postnatally, coinciding approximately with the normal mid‐third week transition from infantile to mature locomotion. Ablation of the MSC at birth revealed that while the MSC‐CST was not essential for ordinary locomotion on flat terrain, its presence hastened normal development of this kind of movement, and that it was absolutely essential for locomotion on difficult terrain. The MSC quadrants showed quite different, and in some domains mutually exclusive, CST projection patterns to forebrain, diencephalon, brain stem, and spinal destinations (determined by Fink‐Heimer‐Nauta fiber degeneration studies). Ablation of some quadrants produced distinctive syndromes of disordered movement: the posterolateral quadrant related to active grasping in positioning limbs, while the posteromedial quadrant related to tactile motorsensory positioning of limbs. Thus in addition to the classic somatotopic organization of the MSC, there was another kind of organization into regions concerned with components of integrated movement of a number of parts of the body. Several forms of aberrant circuitry developed after MSC ablations in infants, but their possible roles in functional adaptation remain to be determined.
Light and electron microscopic studies of postcapillary venules in developing human fetal lymph nodes
Authors: Bailey Raymond P. , Weiss Leon 
Published: February 2005

AbstractDeveloping lymph nodes from 30 human fetuses with crownrump lengths (CRL) of 38 mm (8.7 wk) to 245 mm (26 wk) were studied by light and electron microscopy. Blood vessels that appear to be postcapillary venules (PCV) are present in nodes of 47 mm CRL and older fetuses. These venules first appear in nodes when the nodal population of lymphocytes is sparse. In these early nodes PCV are distributed randomly and consist of a low endothelium, underlying basal lamina and incomplete pericyte sheath. Early nodal PCV are distinguished from other nodal blood vessels by the presence of lymphocyte diapedesis and several luminal lymphocytes.In the late stages of nodal development PCV are the more common noncapillary blood vessel and appear in the parenchyma near the periphery of the node. Late nodal PCV are generally characterized by a cuboidal endothelium that is rich in Golgi apparatus, lysosomes and Weibel‐Palade bodies. The lumen and wall of late nodal PCV contain lymphocytes.The relationship between the development of the parenchyma of fetal nodes and the appearance and activity of PCV, the passage of lymphocytes through the PCV wall and the fine structure of developing PCV are described. It is suggested that the lymphocytes that first appear in developing nodes, and the majority of the lymphocytes found in late nodes, migrate to the node via the blood vascular system and enter the nodal parenchyma by passing across PCV endothelium.
Morphogenesis of rat lingual filiform papillae
Authors: Baratz Robert S. , Farbman Albert I. 
Published: February 2005

AbstractThe morphogenesis of filiform papillae on rat tongue was investigated with the electron microscope. Tongue rudiments were first seen on the 12th day of gestation. At 15–17 days, dermal papillae had formed and were arranged in hexagonal array on the dorsal lingual surface. Capping each dermal papilla was a two‐layered epithelium that protruded slightly above the lingual surface, thus forming the early filiform papilla. In the next stage of development, at 18–19 days of gestation, the epithelium lining the papilla had differentiated into two cell populations, one producing hard keratin, the other producing soft keratin. Some of the keratinized epithelial cells assumed a position at an acute angle to the tongue surface and extended deep into the epithelium. In the next stage, 20–21 days, a cleft appeared within these angularly oriented cells. This resulted in the division of the epithelium into keratin‐lined individual filiform papillae. Finally, the individual papillae increased in size to the adult form.
Inverse prominence of ependyma and capillaries in the spinal cord of vertebrates: A comparative histochemical study
Authors: Sarnat Harvey B. , Campa Justiniano F. , Lloyd Judith M. 
Published: February 2005

AbstractSpinal cords of 15 species representing six classes of vertebrates and the protochordate amphioxus were examined with histochemical methods for esterase, ATPase, LDH, PAS, and PAS‐phosphorylase. Ependymal and glial cell processes were demonstrated and resembled heavy metal impregnations. Capillaries also were shown. The prominence of glycogen‐rich ependymal structures in the spinal cord of nonmammalian vertebrates, and the increase in intramedullary blood vessels in placental mammals, suggest an inverse relationship between the relative development of the ependyma and of the blood supply. The marsupial opossum has sparseness of both ependyma and capillaries, but exhibits an extensive pattern of branched glial processes in both white and gray matter.
The development of primordial and definitive amniotic cavities in early rhesus monkey and human embryos
Authors: Luckett W. Patrick 
Published: February 2005

AbstractRe‐examination of early rhesus monkey and human embryos in the collection of the Carnegie Institution of Washington suggests that the mechanism of amniogenesis in both is basically similar to that of the hedgehog and vespertilionid bats. A primordial amniotic cavity develops by cavitation within the embryonic mass of 10‐day rhesus monkey, and 7‐day human, blastocysts. This primordial cavity has no relationship initially with the overlying trophoblast, contrary to earlier reports. Subsequently, there is a thinning and peripheral spreading of the epiblastic roof of the primordial cavity, resulting in partial opening of the roof and formation of a slightly cupped embryonic disc. The resulting space is not homologous with the primordial amniotic cavity; instead, it is a transitory tropho‐epiblastic cavity. The definitive amniotic epithelium forms by the upfolding and mitotic proliferation of the margins of the epiblastic disc; this process is completed in 11‐day rhesus, and 9‐day human, blastocysts.Amniogenesis by cavitation is associated with the persistence of polar trophoblast following implantation, and it is suggested that this cavitation process may be essential for providing a free epithelial surface for the morphogenetic movement of epiblastic cells during subsequent formation of the primitive streak.
Correlative microscopy of enamel prism orientation
Authors: Weber Dennis F. , Glick Paul L. 
Published: February 2005

AbstractBoth mature and developing human enamel were studied by correlative light and electron microscopic techniques. Ordinary light microscopic observations of routinely prepared ground sections produced a totally inaccurate impression of enamel prism direction. In contrast, ground sections which were acid‐etched and viewed with phase contrast optics, as well as thin (0.5 μm) sections, were in concert with further electron microscopic preparations. The appearance of longitudinally sectioned prisms as demonstrated on thick ground sections is often the result of structural interrelation between groups of obliquely sectioned prisms. The arrangement between enamel prism heads and tails is often such as to produce the light microscopic appearance of classical enamel cross striations. The production of such optical artifacts may be related to conflicting interpretations concerning enamel cross striations as well as light microscopic descriptions of the histopathology of enamel caries.