bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the presence of bridges linking the inner and outer acrosomal membranes of boar spermatozoa
Authors: Russell Lonnie , Peterson R. N. , Freund Matthew 
Published: February 2005

AbstractThe presence of structures bridging the inner and outer acrosomal membranes of the equatorial segment of boar spermatozoa was clearly demonstrated in cells that have undergone a variety of treatment procedures to displace the electron‐dense contents of the acrosome. En‐face sections show bridges to be punctate and not linearly extensive as might be suggested by sections perpendicular to the flat plane of the head. About 4.5 × 105 bridges, each measuring 7 nm across and spaced 7 nm apart, are arrayed hexagonally in the equatorial segment, but bridges are not present within the principal segment of the acrosome. Short‐term treatment with trypsin partially digests the bridges, but does not disrupt the spacing or strict parallel configuration of equatorial segment membranes. However, short‐term treatment with pronase digests most bridges and effectively disrupts the typical configuration of the equatorial segment. Freeze‐fracture of the cytoplasmic face of the acrosomal membranes of the equatorial segment reveals a pattern throughout the phospholipid layer of the membrane which is similar to the pattern of bridges present in en‐face thin sections of the equatorial segments. The data suggest that numerous bridges link the inner and outer acrosomal membranes of the equatorial segment of the acrosome and they play a major, if not an exclusive, role in maintaining the close spacing and parallel arrangement of the membranes in this portion of the acrosome.
Isolation of lung lamellar bodies and their conversion to tubular myelin figures in vitro
Authors: Sanders Ronald L. , Hassett Robert J. , Vatter Albert E. 
Published: February 2005

AbstractLamellar bodies of type II alveolar epithelial cells are the intracellular storage sites of lung surfactant, while tubular myelin figures are an extracellular surfactant form found in the alveolar fluid. A refined procedure was used to isolate intact lamellar bodies from rat lung homogenates in a fraction of high purity and yield. The stability of isolated lamellar bodies under various conditions was determined by electron microscopy. Lamellar bodies were completely disrupted after incubation at 37, 24, and O°C for 0.6, 2, and 12 hr, respectively, in 0.33 M sucrose, 0.01 M HEPES (pH 7.4). In addition, they were completely disrupted after incubation for 1 hr in 0.33 M sucrose, 1 mM EGTA at 0°C or 0.154 M NaCl or 0.10 M sodium phosphate (pH 7.4) at 24°C. Incubation of isolated lamellar body fractions in medium containing 5 mM Ca++ or Mg++ at 37°C for 1 hr resulted in the appearance of tubular myelin figures. A procedure is also presented for the isolation of tubular myelin figures from rat lung lavage fluid.
Effects of antigen dosage on early localization of specific antibodies in rat splenic germinal centers
Authors: Steven William M. 
Published: February 2005

AbstractIn order to identify the initial site of antibody formation in rat spleen, an investigation was made to determine the effects of different antigen dosages on the localization of specific antibodies against sheep erythrocytes (SRBCs). Sixty rats were intravenously injected with 1 ml of either 1%, 5%, or 10% suspensions of SRBCs and killed at days 1, 2, 3, and 4 after immunization. A tissue agglutination procedure in which the binding of SRBCs to cryostat sections of spleen was used to localized anti‐SRBC antibodies. Sections used for determination of SRBC binding patterns, and adjacent sections were stained for histological localization or processed for the determination of acid phosphatase (ACP) activity.Spleens of non‐immunized rats showing binding of SRBCs closely associated with the ACP‐positive marginal metalophils and marginal zone macrophages. This binding was not inhibited by preincubating the sections with 2‐mercaptoethanol. The bound SRBCs lysed when incubated with complement. The initial change that occurred after antigen injection was binding over the germinal centers and coronal regions, and heavier binding over the marginal zones that was not associated with ACP‐positive cells. In animals immunized with 1% SRBCs, these changes were seen on the third day after immunization. In animals immunized with 1% SRBCs, these changes were seen on the third day after immunization. In animals immunized with 5% or 10% suspensions of SRBCs, these changes occurred 24 hours after immunization, during dissociation of the germinal centers. In later stages there was heavy binding of SRBCs over the white pulp and over the red pulp. Binding induced by immunization was inhibited by pretreating the sections with 2‐mercaptoethanol and the bound cells lysed in the presence of complement. The results obtained suggest that IgM antibody to SRBCs appears in the germinal centers at least as early as in the marginal zone or peripheral periarterial region, and support the view that germinal centers may participate in primary antibody responses.
A light and electron microscopic study of the region of cartilage resorption in the embryonic chick femur
Authors: Sorrell J. Michael , Weiss Leon 
Published: February 2005

AbstractIt has long been known that uncalcified cartilage of embryonic chick long bones is removed to make way for invading marrow. However, no one has clearly established which cells are responsible for this erosion. Using the light and electron microscopes, we have studied the cartilage‐marrow interface, which we presume to be the region of resorption. Here, we found two types of mononuclear cells in intimate contact with cartilage matrix. 1. The predominate cell type had a euchromatic nucleus with a nucleolus and a cytoplasm containing extensive profiles of rough endoplasmic reticulum; also, processes extended from these cells into the adjoining cartilage matrix. 2. Macrophages containing many lysosomal vesicles, which often became swollen, were found on or near the surface of cartilage. In addition, a few cells with an intermediate appearance were present. A decrease in the amount of sulfated material in a 25–30 μm zone of cartilage in advance of the interface and an alteration in the orientation, and in some cases the integrity, of collagenous fibers were associated with the presence of the above mentioned cells. These alterations in cartilage were not due to the synthesis of sulfated or of collagenous material. The above evidence, although not conclusive, suggests that these mononuclear cells are responsible for cartilage resorption. In this respect, the removal of avian uncalcified cartilage is similar to the resorption of uncalcified articular cartilage which occurs in rheumatoid arthritis.
The use of computer imaging techniques to visualize cardiac muscle cells in three dimensions
Authors: Marino Thomas A. , Cook P. Nong , Cook Larry T. , Dwyer Samuel J. 
Published: February 2005

AbstractAtrial muscle cells and atrioventricular bundle cells were reconstructed using a computer‐assisted three‐dimensional reconstruction system. This reconstruction technique permitted these cells to be viewed from any direction. The cell surfaces were approximated using triangular tiles, and this optimization technique for cell reconstruction allowed for the computation of cell surface area and cell volume. A transparent mode is described which enables the investigator to examine internal cellular features such as the shape and location of the nucleus. In addition, more than one cell can be displayed simultaneously, and, therefore, spatial relationships are preserved and intercellular relationships viewed directly. The use of computer imaging techniques allows for a more complete collection of quantitative morphological data and also the visualization of the morphological information gathered.
Histochemical study of long nuclear chain fibers in the cat muscle spindle
Authors: Kucera Jan 
Published: February 2005

AbstractCat intrafusal muscle fibers were examined histochemically in serial transverse sections of tenuissimus muscle spindles. The “myofibrillar” adenosine triphosphatase staining reaction was used to recognize the nuclear bag and the nuclear chain fibers in 309 spindle poles. Poles of 40 nuclear chain fibers extended for 1,000 μm or more beyond the termination of the spindle capsule. These long chain fibers stained less intensely for nicotinamide adenine dinucleotide tetrazolium reductase (NADH‐TR) than the typical chain fibers of shorter polar length. In sections stained for cholinesterases (ChE), the extracapsular regions of most long chain fibers displayed one or two short, dense “plate”‐type ChE deposits, which may represent the terminals of skeleto‐fusimotor axons. In addition, about one‐third of the long chain fibers displayed one or more thinner and smaller areas of ChE activity, possibly corresponding to the endings of fusimotor axons. The overall ChE staining pattern of the typical chain fibers was unlike that of the long chains. However, some of the shorter nuclear chain fibers resembled long chain fibers with the NADH‐TR reaction, even though their ChE “plates” were located intracapsularly.It is concluded that nuclear chain fibers in the cat spindle form a class of intrafusal fibers with heterogeneous histochemical properties, and that the long chain fibers represent one fiber subtype.
Indirect immunofluorescent staining of fibronectin associated with the floor of the foregut during formation and rupture of the oral membrane in the chick embryo
Authors: Waterman Robert E. , Balian Gary 
Published: February 2005

AbstractThe distribution of the glycoprotein, fibronectin, within the cranial region of stage 8–16 chick embryos was examined by indirect immunofluorescence using paraffin sections exposed to affinity‐purified rabbit anti‐human CIG and FITC‐conjugated goat anti‐rabbit immunoglobulins. Fluorescence was present within the matrix surrounding the cranial mesenchyme, along the basal surfaces of all epithelia, and surrounding the notochord at all stages. Fluorescence associated with the floor of the foregut was particularly intense. The fluorescent layers beneath the ectoderm and endoderm of the oral (oropharyngeal) membrane at stage 8 merged into a single, continuous, intensely fluorescent line as the extra‐cellular space within the oral membrane narrowed during stages 9–12. This line of uniform fluorescence parallels the previously described histological reorganization of the extracellular compartment of the oral membrane, but the ultrastructural localization of this fluorescent material remains unknown. Fluorescence was also intense beneath the foregut endoderm in the presumptive cardiac region caudal to the oral membrane and was continuous with strands of fluorescent material extending into the matrix of the dorsal mesocardium and cardiac jelly of the developing tubular heart. These observations indicate that the extracellular matrix associated with the floor of the entire foregut contains fibronectin during stages encompassing the formation and rupture of the oral membrane. The presence of fibronectin within the oral membrane and dorsal mesocardium, as well as between Rathke's pouch and infundibulum and within the closing plates between ectodermal clefts and endodermal pouches, is consistent with the possibility that this glycoprotein may play a role in adhesion at these sites.
Fine morphological characteristics and microtopography of the free nerve endings of the human digital skin
Authors: Cauna Nikolajs 
Published: February 2005

AbstractBlocks of osmium‐fixed human digital skin, representing a total area of 5 sq mm, were cut serially parallel to the skin surface starting with the epidermis for electron microscopical studies. At intervals, single 1‐μ sections were taken and used for recording the microtopography of the receptor organs at various levels. Graphic reconstructions of 28 nerve endings were made.It was found that the digital skin accommodated up to 80 dermal papillae and three to four sweat duct orifices per square millimeter. Each papilla contained one to three fenestrated capillary loops. More than 60% of all papillae contained free nerve endings, sometimes up to five in a single papilla. As a result, up to 100 free nerve endings were counted per square millimeter. Intraepidermal endings were also present, one to five per square millimter. No endings of any kind were found within the boundary zones between the papillary ridges and in the immediate vicinity of the sweat ducts.The origin of a free ending was marked by the perikaryon of a modified Schwann cell, which constituted the terminal cell of the Schwann sheath. The perikaryon was situated at the base of the dermal papilla, while its distal process provided the cytoplasmic sheath to the axon terminals and their branches. Sometimes two endings merged into a single receptor organ. The terminal Schwann cell frequently served as a rallying point of endings. Three morphological kinds of free endings were observed: open endings, beaded endings, and plain endings. The intraepidermal endings were the derivatives of the plain endings.The free endings in the digital skin had essentially vertical distribution. Each ending covered a minute surface area of skin in a punctate pattern. This is in contrast to the mode of distribution of the free (penicillate) endings of the human hairy skin. Each penicillus covers a large horizontal skin area and overlap̀s that of their neighbors.
A histochemical and ultrastructural study of serotonin‐containing nerves in cerebral blood vessels of the lamprey
Authors: Iijima Tadahiko , Wasano Takeo 
Published: February 2005

AbstractLamprey, Entosphenus japonicus, cerebral blood vessel autonomic nerve supply was studied with fluorescence and cholinesterase histochemistry and electron microscopy.Nerve fibers emitting a yellow fluorescence characteristic of serotonin (Exc./Em. max.; 380/530 nm) were found on the major cerebral and pial arteries, but not acetylcholinesterase (AChE)‐positive ones. Single ganglion cells also emitting a strong yellow fluorescence were seen in the artery adventitia. On rare occasions these cells were observed in pairs. Terminal varicosities of central catecholamine‐containing nerves (Exc./Em. max.; 410/475 nm) were observed on parenchymal capillaries, but not central AChE‐positive nerve terminals.In ganglion cells, dense cored vesicles (ca. 130 nm in average diameter; DCV) were abundant in the Golgi area, suggesting their formation at this site. Two types of DCV were observed; one with a homogeneous dense core and the other with a granular core. DCV were numerous in axons as well, axons in which many small clear vesicles (40–60 nm in diameter) as well as DCV were occasionally observed. The question of whether the small clear vesicles or the DCV contained serotonin could not be resolved.
Traversing filaments in desmosomal and hemidesmosomal attachments: Freeze‐fracture approaches toward their characterization
Authors: Kelly Douglas E. , Kuda Aileen M. 
Published: February 2005

AbstractDesmosomes and hemidesmosomes from larval newt epidermis were examined by freeze‐fracture methods incorporating low osmolality fixation, short duration glycerination, complementary replica comparison, stereo imaging, and dark shadow printing. These procedures provide new evidence regarding the structure of “traversing” filaments as mediators of attachment between intermediate filaments and the cell membranes of desmosomes and hemidesmosomes. A detailed analysis of intramembranous particles and other structure in these attachments has also been possible. The relationship of this evidence to models of desmosomal structure suggested by other authors is discussed.
Tridimensional study of the deep cortex of the rat lymph node. I: Topography of the deep cortex
Authors: Bélisle C. , Sainte‐Marie G. 
Published: February 2005

AbstractDiagrams of the lymph node currently represent its deep cortex (paracortex) as a layer of rather uniform thickness underlying the whole peripheral cortex. However, this concept has not been supported by actual observations; previous nvestigators have observed, instead, related structures whose appearance varied greatly from nodule‐like to ill‐defined components. Clearly, the present knowledge of the histology of the deep cortex is inadequate and confusing. Therefore, we undertook a tridimensional study of the region in different nodes of rats. The present work, bearing on the topography of the region, revealed that the deep cortex of the rat node is formed of one to several basic “units”. Each unit is a semi‐rounded structure, varying from semispheric to semi‐ovoid in shape and contiguous to a portion of peripheral cortex. The work further showed that two to several units can fuse to form a “complex”. The data indicated that the number, the size and the shape of the units and/or of the complexes of a node differ to some extent according to its anatomical location. These differences probably reflect corresponding variations in the nature and importance of the antigenic stimulation in the different sites of the organism. Finally, the study demonstrated the necessity of tridimensional examination of a node to obtain adequate information on its overall architecture and, particularly, on its deep cortex topography.
Mouse uterine glands during the peri‐implantation period II. Autoradiographic studies
Authors: Given Randall L. , Enders Allen C. 
Published: February 2005

AbstractProtein synthesis and secretion in mouse uterine glands during the peri‐implantation period were studied, by both light and electron microscopic autoradiography, after the in vivo administration of tritiated leucine (3H‐leucine) and proline (3H‐proline). Light microscopic autoradiography revealed that the time course of synthesis and secretion of labeled proteins was constant during days four, five, and six of pregnancy. Labeled material could be detected in the glandular lumen by 45 minutes after administration and in higher concentrations by 90 minutes after administration.Analysis of electron microscopic autoradiographs from days five and six of pregnancy showed that high levels of activity were initially present over the rough endoplasmic reticulum and Golgi complexes and subsequently declined at the longer time intervals (45 and 90 minutes), while activity over the glandular lumen increased with time. The pathway of intracellular transport to the glandular lumen appeared to be via small cytoplasmic vesicles on both days five and six of pregnancy. Additional pathways for transport of the labeled protein to the glandular lumen appeared to be present in the form of the large vesicles on day five and granules on day six of pregnancy.Throughout the peri‐implantation period, mouse uterine glands were active secretory structures in which the mode of secretion was similar to other exocrine cells. Thus, the uterine glands of the mouse must be considered a source of uterine fluid proteins at the time of implantation that may contribute to quantitative changes in these proteins.
Ultrastructural events during early gonadal development in Rana pipiens and Xenopus laevis
Authors: Merchnt‐Larios Horacio , Villalpando Irma 
Published: February 2005

AbstractThe establishment of the undifferentiated gonad was studied in Xenopus laevis and Rana pipiens using high resolution techniques. It was found that the cells of the so‐called “mesonephric blastema” had no structural resemblance to the cells of the gonadal medulla in both species. Furthermore, there was no morphological evidence that would suggest a migration of the former cells towards the incipient gonad at the time of its appearance. However, the basal lamina of the coelomic epithelium was interrupted in the region of the genital crest, and there was a definite ultrastructural similarity between the cells of this epithelium and those that first form the medulla. These observations suggest that, in amphibians, the cells of the gonadal medulla come from a cellular line arising from the coelomic epithelium and not from the “mesonephric blastema,” as has been proposed.
Secretion granule formation in the rabbit parotid gland after isoprenaline‐induced secretion: Stereological reconstructions of granule populations
Authors: Cope G. H. , Williams M. A. 
Published: February 2005

AbstractThe development of the secretion granule population of rabbit parotid glands after isoprenaline (IPR)‐induced degranulation has been analyzed at the E.M. level using stereological techniques. Young male New Zealand White rabbits were sacrificed 2, 4, 8, 12 and 16 hours after IPR administration and the granule populations compared with those of starved controls. In controls. In control glands a third of cell volume was occupied by stored secretory material, and it was estimated that, on average, cells contained 386 granules. The granule population as a whole had a mean diameter of 0.94 μm, with a unimodal positively skewed size distribution. Two hours after IPR treatment overall granule volume density was only 15% of that of control glands, but there was evidence that the process of restitution had already begun. At 8 hours about a fifth of acinar cell volume was occupied by electron‐dense granules with an estimated mean diameter of only 0.58 μm, and the population as a whole was more strongly skewed than in the controls. In the later stages of restitution (12 and 16 hours), the volume of stored secretory material continued to rise, mean granule diameter increased, the size‐frequency distribution became less skewed and the estimated number of granules per cell fell to 277 by 16 hours, suggesting that some granule fusion occurs during development.The analyses are discussed in relation to the techniques employed, and the results are equated with other independent evidence of the mode of granule genesis.
Ultrastructure of the developing vascular system in the puppy kidney
Authors: Evan Andrew P. , Hay Don A. 
Published: February 2005

AbstractThe present study defined the ultrastructural features of peritubular capillary development. Two‐day‐old beagle puppies and adult dogs were perfused with 2.5% glutaraldehyde and routinely prepared for light and transmission electron microscopy. Some of the fixed tissue was subsequently used to make freeze‐fracture replicas.The outer cortex of the puppy kidney possessed large, thick‐walled vessels best termed sinusoidal capillaries instead of the small caliber vessels (peritubular capillaries) noted in the adult. These sinusoidal vessels showed extensive overlapping of the endothelium with isolated patches of fenestrae. Their luminal surfaces were irregular, owing to prominent ridges and sporadic bulges of endothelium. The basement membrane of most vessels was not present. Interstitial spaces were filled with mesenchymal cells and cells closely resembling pericytes. The diameter of the fenestrae of vessels throughout the cortex was similar; however, the number of fenestrae per micrometer of endothelium increased significantly from outer to inner cortex. Vessels of the inner cortex were also immature when compared to the adult. From these morphological findings, it was apparent that a true peritubular capillary system does not exist in the two‐day‐old puppy. Ultrastructural features of these vessels suggested reduced permeability characteristics.