bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thymic morphology during in vitro culture
Authors: Eerola E. , Ekfors T. , Tammi R. , Ruuskanen O. 
Published: February 2005

AbstractMorphology of guinea‐pig thymic fragments was studied sequentially during in vitro organ culture by using light and electron microscopy and 3H‐thymidine autoradiography. In culture the fragments became alymphoid. Thymic lymphocytes started to disappear first at the corticomedullary border, which gradually broadened, giving rise to alymphoid epithelial fragments. As the lymphoid cells disappeared the thymic epithelium began to transform into a keratinized squamous epithelium. The keratinization started in the cells surrounding the Hassall's corpuscles, causing the enlargement of the corpuscles and finally total keratinization of the cultured epithelial fragments. In autoradiographic studies cell proliferation could be observed in uncultured thymuses at the cortical pericapsular area. In cultured alymphoid fragments labelled cells were distributed diffusely in the epithelium. Later labelling was concentrated to epithelial cells transforming to keratinized epithelium. Ultrastructural studies similarly showed transformation of the epithelial cells to squamous keratinized epithelium. The observation support the view that Hassall's corpuscles are derived from the keratinized thymic epithelium and that their existence is connected to the normal function of the epithelium.
Innervation of rat molar teeth: I. Distribution of neuronal cell bodies in the trigeminal ganglion from a mandibular molar tooth
Authors: David Aker F. , Reith Edward J. 
Published: February 2005

AbstractThe cell bodies of neurons innervating a rat mandibular molar tooth were examined with respect to their location in the trigeminal ganglion. The study sought to determine if these cell bodies were restricted to a specific somatotopic location within the mandibular territory of the ganglion or if they were distributed throughout the entire mandibular territory. Horseradish peroxidase (HRP) pellets were placed in the cavity preparation of right first mandibular molar teeth for a 24‐hour period. The animals were then perfusion fixed, and the right trigeminal ganglion was removed, sectioned and processed by the tetramethyl benzidine neurohistochemical technic.The four trigeminal ganglia constituting this experimental series demonstrated 129, 185, 236, 318 HRP‐positive cell bodies. These cell bodies were dispersed throughout the extent of the mandibular territory. It was concluded from these observations that the distribution of cell bodies innervating a rat mandibular molar tooth is not restricted to a specific region of the mandibular territory of the trigeminal ganglion, but rather the distribution of these cell bodies is throughout all parts of the mandibular territory.
A method of study of the pathology of the conduction system for electrocardiographic and his bundle electrogram correlations
Authors: Lev Maurice , Bharati Saroja 
Published: February 2005

AbstractThere have been advances in electrophysiology which have necessitated a more thorough semi‐quantitative analysis of the entire conduction system to yield data useful for correlation purposes. Thus an attempt is made to modify and expand our previous method of studying the conduction system pathologically. This method thus includes the study of the sinoatrial (SA) node and its approaches, the atrial preferential pathways, the approaches to the atrioventricular (AV) node, the AV node, the penetrating and branching portions of the AV bundle, the bundle branches, the peripheral Purkinje nets, and the remainder of the atrial and ventricular myocardium.The SA node and its approaches are studied in a longitudinal manner. This gives a better insight into the pathologic changes than does a study in the transverse direction. The approaches to the AV node, bundle and bundle branches are studied in an oblique manner, rather than horizontally apicalward, or from the posterior to the anterior septal region. The horizontal manner does not give sufficient sampling of the AV node and bundle unless complete serial sections are made. Sectioning from the posterior to the anterior septal wall makes difficult an evaluation of the right bundle branch.In conduction system correlation with Wolff‐Parkinson‐White and Lown‐Ganong‐Levine syndromes complete serial sectioning of both AV rims is advisable. Where complete serial sectioning is impossible in large adult hearts, retaining every fifth section may be permissable. In the study of congenitally abnormal hearts, it is advisable to embed the entire heart as a unit. If that is impossible because of the size of the heart, then very careful judicious planning of the fashioning of the blocks is necessary, so that displaced SA nodes, and anterior AV nodes and bundles are not overlooked.
The internodal atrial myocardium
Authors: Anderson Robert H. , Ho Siew Yen , Smith Audrey , Becker Anton E. 
Published: February 2005

AbstractThe anatomical substrates of internodal conduction have long been a contentious topic. Debated first by the German Pathological Society in 1910, the consensus of established opinion for over half a century was that conduction between sinus and atrioventricular nodes occurred through plain myocardium. This was a conclusion supported by Truex in 1961. Despite his restatement of this fact in 1976, it has become fashionable to describe internodal conduction as being mediated by specialized internodal pathways. To reinvestigate this problem we studied 22 human fetal and 32 human infant hearts. In each case it was possible to cut the atrial tissues as a single block of tissue and to examine serial sections through the internodal myocardium. The sinus node, atrioventricular node, and segments of atrioventricular ring specialized tissue were recognized as specialized tissue using the light microscope in each heart. In contrast, there was nothing “special” about the myocardium between the nodes, nor was it possible to recognize tracts on the basis of either histological appearance or cellular architecture. It is concluded that, from the standpoint of light microscopy, there is no evidence whatsoever to support the purported concept of specialized anatomical substrates for internodal conduction.
Ephemeral, rudimentary glomerular structures in the mesonephros of the mouse
Authors: Zamboni Luciano , Upadhyay Shakti 
Published: February 2005

AbstractThe fine morphology of glomeruli present in the mesonephroi of mouse embryos from days 12 to 14 of gestational age is described. The glomeruli are rudimentary, ephemeral structures which probably result from temporary juxtaposition of a blood capillary to the ventral extremity of a mesonephric tubule. Yet, they might possess a certain degree of functionality.
The fine structure of the placental labyrinth in the sloth, Bradypus tridactylus
Authors: King Barry F. , Pinheiro Paulo B. N. , Hunter Robert L. 
Published: February 2005

AbstractThe placental labyrinth of the three‐toed sloth (Bradypus tridactylus) was examined by electron microscopy. The material available was from two fetuses of 55 mm and 150 mm crown‐rump length (CRL). The placenta of the younger specimen was a transition form between the syndesmochorial type and the endotheliochorial type. The interhemal membrane of the 55 mm CRL specimen consisted of the following components: (1) hypertrophied maternal endothelial cells surrounding the maternal vessels; (2) a small amount of extracellular material and spindle‐shaped cells, both presumed to be of maternal origin; (3) a layer of syncytial trophoblast that had an unusual, reticulated or sponge‐like appearance; and (4) the fetal capillary endothelium. In addition, the fetal connective tissue contained hypertrophied mesenchymal cells that were characterized by abundant granular endoplasmic reticulum. The placenta of the 150 mm CRL fetus was poorly preserved, but it was possible to determine that the placenta was of the endotheliochorial type. There was a close apposition of maternal endothelium and trophoblast. The results confirmed virtually all of the light microscopic observations of Wislocki (1927; 1928b). The ultrastructure of the sloth interhemal membrane is compared to that of other endotheliochorial placentas, particularly that of the shrew, with which it shows many cytological similarities.
The fate of sperm after vasectomy in the hamster
Authors: Flickinger Charles J. 
Published: February 2005

AbstractYoung adult male hamsters were subjected to bilateral vasectomy. The reproductive tracts were studied by light and electron microscopy at intervals up to 1 year after the operation. Sperm continued to be produced, since testicular alterations were focal. Spermatic granulomas were associated with the excurrent ducts of all animals 5 months or 1 year after vasectomy and with those of one of four hamsters 2 weeks after the operation. Phagocytosis of sperm in the lumina of the efferent ducts and proximal parts of the epididymis, and disintegration of membranous components of intraluminal sperm occurred in approximately three‐fourths of the animals studied 5 months or more after vasectomy. The results indicate that after vasectomy in the hamster sperm are disposed of by phagocytosis in spermatic granulomas, intraluminal phagocytosis, and dissolution in the lumen of the male ducts, although the latter process may be incomplete.
Plexus muscularis profundus and associated interstitial cells. I. Light microscopical studies of mouse small intestine
Authors: Rumessen Jüri Johannes , Thuneberg Lars 
Published: February 2005

AbstractThe zinc iodide/osmic acid (ZIO) method was used in a modification that selectively stained nerves and associated interstitial cells of Cajal (ICC ) of muscularis externa. Due to its selectivity the method allowed a detailed stereoscopical analysis of whole mounts with respect to the topography and morphology of these elements. The method thus assisted and expanded our ultrastructural studies. The ZIO staining allowed a distinction of four morphologically different interstitial cell types (ICC‐I‐IV) confined to four compartments. The stained components were: (1) A rich plexus of highly ramified intestitial cells (1CC‐II) in the subserous laver. (2) Auerbach's plexus with an associated extensive plexus of interstitial cells (ICC‐I) in close contact with tertiary fasciculi. (3) Nerve fasciculi of the outer division of the circular muscle layer. These formed a nerve plexus in a well‐defined plane in the outermost cell layers (plexus muscularis super‐ficialis), with few fasciculi located internal to this plexus. A few bipolar interstitial cells (ICC‐IV) were associated with nerve fasciculi of this region. (4) A nerve plexus located in the region between the two subdivisions of the circular muscle, plexus muscularis profundus (PMP). PMP was revealed throughout the small intestine as a continuous network of elongated, circularly oriented meshes. The pattern of connections between PMP and the other enteric plexuses was studied stereoscopically. Ganglion cells intrinsic to PMP occurred widely scattered. Interstitial cells associated with PMP (ICC‐III) were arranged in a plexiform manner; their morphology and relations to nerves were investigated in great detail. A selective innervation of ICC‐III via axons of PMP was strongly supported.
Sequence of ossification in human vertebral neural arch centers
Authors: Ford D. M. , McFadden K. D. , Bagnall K. M. 
Published: February 2005

AbstractThe purpose of the present study is to determine whether ossification of the human vertebral neural arches follows a craniocaudal sequence of development or develops in separate groups from the lower cervical/upper thoracic, upper cervical, and lower thoracic/upper lumbar regions as described by Bagnall et al. (1977b) in a radiographic study.Seven formalin‐fixed, two fresh frozen, and six serial‐sectioned human embryos and fetuses, ranging in crown‐rump length (C‐R) from 27 mm to 76 mm, were examined. A procedure adapted by Watson (1977a,b) for in toto staining of whole specimens with alcian blue and alizarin red S for cartilage and bone was used, whereas serial sections were stained with hematoxylin and eosin, or Koneff's stain (1960). The intact specimens demonstrated a vivid deep blue cartilaginous skeleton with differentiated red areas of bone development seen through soft tissues rendered transparent by potassium hydroxide or enzyme clearing. The ossification sequence of the neural arches differed from the conventional craniocaudal descriptions given in anatomical textbooks. Neural arch ossification was found to commence in the lower cervical/upper thoracic regions, quickly followed by a second group in the upper cervical region, and subsequently a third group in the lower thoracic/upper lumbar region.
Persistent left hepatic venous connection with the coronary sinus
Authors: Bunger Paul C. , Parke Wesley W. 
Published: February 2005

AbstractAn anomalous direct connection between the left hepatic vein and the coronary sinus in two cadavers is described. The normal development of the central systemic venous system with particular reference to the hepatic region is reviewed and a possible explanation for the present configuration is put forth. Although this configuration of venous anomaly without abnormal shunting of blood is considered clinically insignificant, the association of cardiac arrhythmias with these variations heightens the importance of their identification.
Pulmonary alveolar pores and alveolar macrophage‐mediated particle clearance
Authors: Ferin J. 
Published: February 2005

AbstractPulmonary alveolar macrophages (AM) are considered to have an essential role in alveolar clearance of particles. The AM occupy only a small portion of the alveolar surface and their number is probably lower than the number of alveoli. Even at realistic experimental exposures the number of deposited particles, which are distributed all over the lung surface, is orders of magnitude higher than the number of AM. Phagocytosis of deposited particles, however, is being accomplished rapidly within hours. Based on microscopic evidence, we suggest that alveolar pores serve as important passageways for AM by shortening the distance between particles and AM. Accordingly, the pores of Kohn may, in part, lend efficiency to the in vivo particle collection by AM.
Chemotherapy does not affect the development of inter‐sertoli junctions in childhood leukaemia
Authors: Camatini Marina , Franchi Emilia , de Curtis Ivan , Anelli Giuliana , Masera Giuseppe 
Published: February 2005

AbstractThe inter‐Sertoli junctions of children aged between 5 and 12 years, affected by acute lymphoblastic leukaemia, were analyzed in sections and freeze‐fracture replicas. The testicular biopsies were performed at the end of therapy, when patients were in continuous remission for over 30 months. Chemotherapy does not seem to affect the development of junctions that were studied in sections and freeze fracture. Two age groups were considered (I, 5 to 8 years; II, 9 to 12 years). In age group I, oval Sertoli cells were connected by occasionally focal points of fusion, which in replicas appeared as scattered, interrupted ridges on the P face and grooves on the corresponding E face. In age group II Sertoli cells presented cytoplasmic extensions and interdigitations. Tight junctions appeared close to one another in conventional sections. Freeze fracture evidenced extensive although isolated areas formed by intervining strands. Lanthanum penetrated freely the intercellular spaces and gap junctions were observed in both age groups. The results suggest that tight junctions formation is initiated long before puberty; a progression in the complexity of the strand organization is present as the tubules mature; the strands reorganize in parallel and continuous rows only at puberty.
Membrane differentiation in the golgi apparatus of mammalian urinary bladder epithelium
Authors: Alroy Joseph , Merk Frederick B. , James Morré D. , Weinstein Ronald S. 
Published: February 2005

AbstractThe endomembrane system in superficial and intermediate epithelial cells of mammalian urinary bladder was studied by cytochemistry, thin‐section and freeze‐fracture electron microscopy to determine the sites where special forms of membrane differentiation first appear. Glutaraldehyde‐resistant NADH‐ferricyanide reductase, distinctive 11–12 nm intramembrane particles (IMP), and asymmetry of membrane leaflets served as markers of membrane maturation. The three markers were specifically associated with the maturing face of Golgi apparatus and were absent from the remainder of the endomembrane system. Activity of this enzyme was associated with the lateral regions of the maturing face, fusiform vesicles, and the plasmalemma. Asymmetric unit membrane (AUM) plaques were not observed in the Golgi apparatus per se but were present in immature fusiform vesicles that had not detached from the maturing face. When freeze‐fracture replicas and thin sections were compared, randomly arranged 11–12 nm IMP first appeared in maturing face membranes that were adjacent to clusters of “free” polyribosomes in the Golgi apparatus region. The proximity of these polyribosomes suggests that they may be related to the coincident appearance of the 11–12 nm IMP in the maturing face membrane. Our observations support the hypothesis that membranes undergo differentiation during “flow” through compartments of the endomembrane system. The lateral regions of the maturing face of the Golgi apparatus appear to be a critical location for the morphogenesis of plasma membranes in urinary bladder.
Scanning electron microscopy studies of the vascular pole of the rat glomerulus
Authors: Frank Martina , Kriz Wilhelm 
Published: February 2005

AbstractThe vascular poles of 30 renal corpuscles were studied in critical‐point dried renal cortex of the Munich‐Wistar rat by scanning electron microscope (SEM). In 28 cases one afferent and one efferent arteriole were observed; one afferent and two efferent arterioles were found in two cases only. The same study was done in the Sprague‐Dawley rat, where 34 renal corpuscles were examined. One afferent and a single efferent arteriole were found in 32 cases; in one case only one afferent and two efferent arterioles were observed. In another case it was questioned whether a single or a double efferent arteriole arteriole is present. In addition, the specimens allowed an evaluation of the area where the extraglomerular mesangium passes into the mesangial cells of the glomerular tuft. This area was found to be rather small to represent a “punctum fixum” for a contraction of the entire mesangium.
Freeze‐fracture studies of neonatal mouse incisors
Authors: Hasty David L. 
Published: February 2005

AbstractDifferentiation of preodontoblasts to odontoblasts and preameloblasts to ameloblasts during development of the mouse mandibular incisor proceeds in a gradient from the area of the odontogenic organ, where undifferentiated ectomesenchymal and epithelial cells proliferate, toward the incisal tip where mature tooth tissues, dentin and enamel, are present. The freeze‐fracture technique has been used in the work presented here to study cell membrane ultrastructure of preodontoblasts and preameloblasts at several stages of differentiation. At early stages of differentiation, cuboidal preameloblasts are joined together distally by numerous gap junctions. Relatively fewer junctions occur elsewhere on the lateral plasma membranes, but gap junctions frequently occur proximally between preameloblasts and stratum intermedium cells. As differentiation proceeds and the cells become columnar, distal and proximal junctions persist. Tight junctions, however, were not observed at any of the stages studied. Intramembrane particle concentration of the lateral preameloblast plasmalemma appears to increase as differentiation proceeds. Odontoblasts are also joined distally by numerous gap junctions which persist through later stages of differentiation. Although odontoblast cell processes were observed to project toward the preameloblast layer, no clear points of cell to cell contact or defined intercellular junctions between the two cell types were observed.
Dynamics of lysosomal elements in pulmonary alveolar macrophages: II. Transitory intracytoplasmic events in activated cells
Authors: Sorokin Sergei P. 
Published: February 2005

AbstractIntracytoplasmic interactions were examined in iron oxideexposed and ‐unexposed alveolar macrophages of mice by electron microscopy and ultrastructural cytochemistry. Submicronic‐sized particles are taken up by microendocytosis into 800‐Å tubules that sometimes open up into a large vacuole located midway between the plasmalemma and the Golgi complex and sometimes lead directly to that organelle, which is reactive for acid phosphatase while cells are only modestly engaged in lysosomal synthesis and then serves as the main locus for formation of heterolysosomes. In more activated cells, nascent lumbricoid lysosomes are budded directly off branches of the granular reticulum; in consequence, much of the newly synthesized acid phosphatase bypasses the Golgi apparatus, and heterolysosomes are formed throughout a widened expanse of cytoplasm. The lumbricoids exist either as free elements or as a labyrinthian network of lumbricoid units, and the two forms appear interconvertible. They are short lived in contrast to larger rounded lysosomes more commonly present, many of which are heterolysosomes as judged by their content of ingested particles. Lumbricoids readily fuse with exoplasmic structures; indeed, in some lumbricoid‐producing cells terminal segments of the reticulum may share this propetry to a degree, since they resemble transitional elements when extended along large phagosomes. Microendosomes can be taken up into lumbriciods, but if the endosome is larger, lumbricoids will adhere to its surface and become part of the digestive vacuole. A labyrinth is formed to envelop large phagosomes or regions of cytoplasm marked for autophagy. The interior is invaded by branches and digestion ensues. In active macrophages the Golgi apparatus is enlarged. The centrioles organize an array of microtubules about themselves, and individual Golgi stacks are turned outward to give the organelle better access to phagosomes and lysosomes. In less active cells the microtubules disappear, and the stacks reform in a circle about the diplosome. Alveolar macrophages therefore make a variety of lysosomes. Depending on cellular activity, one kind or another predominates. Few of them fall cleanly into “primary” and “secondary” classes, and in their interactions with other cellular structures they are influenced by mechanisms operating on microscopic as well as molecular scales.