bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of oxyntic cell membranes during conditions of rest and secretion of HCl as revealed by freeze‐fracture
Authors: Black Joel A. , Forte Trudy M. , Forte John G.
Published: February 2005

The density and distribution of membrane associated particles of piglet oxyntic cell tubulovesicular and apical surface membranes were investigated during resting (nonsecreting) and secreting conditions. For the resting oxyntic cell, the abundant tubulovesicles showed a highly asymmetrical distribution of particles between fracture faces, with the P face heavily studded by particles and the E face particle deficient. The apical surface, however, had a relatively symmetrical distribution of particles on both membrane fracture faces. In contrast to the resting state, the apical surface of the stimulated oxyntic cell showed a marked asymmetry of membrane particles; the P face had a high density of particles, while there was a scarcity of particles on the E face. The observed changes in apical surface membrane particle distribution support the hypothesis that, following the initiation of acid secretion, the tubulovesicles fuse with and become an integral part of the apical surface. Thus, the apical membrane P face of the stimulated cell is enriched and the E face is diluted by the incorporation of tubulovesicular membranes.
Cell interactions between hematopoietic and stromal cells in the embryonic chick bone marrow
Authors: MiChael Sorrell J. , Weiss Leon
Published: February 2005

Light microscopic, scanning electron microscopic, and transmission electron microscopic studies of the early developmental stages of chick embryonic bone marrow disclose characteristic associations of the first hematopoietic cells with stromal cells. The first hematopoietic cells, large basophilic cells that we have termed presumptive stem cells, segregate into erythropoietic and granulopoietic regions. Intravascular erythropoietic cells associate with sinusoidal endothelial cells, while granulopoietic cells associate with extravascular reticular cells. Extensive, intimate contacts between erythroid and endothelial cells are maintained, in part, by marginal arrays of microtubules, which promote a flattening of the adherent erythroid cell surface. In addition, cell surface components of opposing cells, visualized by ruthenium red staining, appear to merge and possibly to interact. Granulopoietic cells establish intimate but less extensive associations with reticular cells through cell‐surface interactions. Stationary granuloid cells appear to be held in place by small, thin processes emanating from the sheet‐like reticular cells. Granuloid cells are capable of moving within the extravascular region, using reticular cell surfaces as a substrate. Intimate associations also occur among granulopoietic cells, the significance of which is unclear. Thus, sinusoidal endothelial cells and reticular cells comprise the critical non‐hematopoietic or stromal elements of avian bone marrow, where they have a putative role in segregating presumptive stem cells into erythrocytic and granulocytic compartments. They serve as an architectual, and possibly regulatory, framework on which hematopoiesis occurs.
The ultrastructural histochemistry and stereoscanning electron microscopy of the rodent and amphibian surfactant systems
Authors: Stratton C. J. , Wetzstein H. Y. , Hardy T.
Published: February 2005

Ultrastructural histochemical procedures were employed to determine the carbohydrate components and their contributions to the rodent and amphibian surfactant systems. Zirconium stained the rodent (rat) cytoplasm surrounding the multilamellar bodies, the Golgi, and was associated with the membrane structures of the compact lamellae of alveolar multilamellar bodies. In the rodent and amphibian (Rana pipiens), ruthenium red stain was observed within all tubular myelin surfactant matricies. The “gutters” tubular myelin surfactant matrix, and intratubular myelin surfactant matrix materials all demonstrated a positive reaction product. The periodic acid‐chromic acid‐silver procedure revealed irregular channels extending from the multilamellar bodies to the surface of the rodent great alveolar pneumocyte.

The extra‐pulmonary and respiratory surfaces in both species were additionally studied by stereoscanning electron microscopy. The respiratory anatomy of the rodent was corroborated. The amphibian lung demonstrated three orders of septa, and in the expired state, tertiary septal pits. The amphibian primary septa were hollow, blind tubules containing respiratory surfaces.
Structure and orientation of extracellular matrix in developing chick optic tectum
Authors: Krayanek Susan
Published: February 2005

The mechanisms underlying directed axonal movement in the developing central nervous system are largely unknown. Histochemical methods for transmission and scanning electron microscopy were used to study the surface of the developing optic tectum in the chick embryo at the time of optic fiber ingrowth.

A highly structured extracellular matrix consisting of fibrillar and granular components was seen in normal and in uninnervated specimens that had been fixed in solutions containing the cationic dyes Alcian blue, ruthenium red, or safranin O. The strong affinity of these stains for glycosaminoglycans suggests that the matrix contains such macromolecular aggregates. With routine fixation methods the matrix was not seen, but empty extracellular spaces were apparent.

The tectal matrix was particularly prominent ahead of the growing front of optic fibers. Its location was thus appropriate for interacting with pioneering axons that cross the surface of the developing tectum along its anteriorposterior axis. Matrix fibrils were organized in a stacked alignment predominantly parallel to the tectal surface, but otherwise their orientation appeared random. The matrix possibly bears on the guidance of optic fibers. However, its geometry suggests that this may involve a mechanism more specific than mechanical contact guidance.
A random arrangement of albumin‐containing hepatocytes seen with histo‐immunologic methods. II. Conditions that produce the artifact
Authors: Lebouton A. V. , Peters Masse J.
Published: February 2005

The cellular immunolocalization of albumin in rat liver has been studied as a function of various physiological and physical conditions. Our observations show that the prime requisite for accurate immunolocalization of albumin and other hepatic‐based proteins is the complete removal of blood and especially plasma from sinusoids and the perisinusoidal space of Disse prior to fixation.

Fixation of blood‐filled liver specimens results in the antifactual entrance of plasma constituents into hepatocytes. When the fixative used is formaldehyde, the artifactual uptake occurs primarily into hepatocytes that have a high glycogen content. Fixation of blood‐filled liver with acetic acid‐ethanol causes a massive influx of plasma into all hepatocytes. On the contrary, with blood‐free liver, varying the type of fixative consistently demonstrates that all hepatocytes normally contain albumin, transferrin, and fibrinogen simultaneously.

Increasing the time between cessation of blood flow and outright fixation by either withholding the fixative or by impeding its diffusion through the specimen causes a progressive loss of antigenicity of albumin. The same result ensues when specimens remain in contact with the fixative for an extended time.
Amplitude‐reduction and acrophase‐advance of circadian mitotic rhythm in corneal epithelium of mice with bilaterally lesioned suprachiasmatic nuclei
Authors: Powell E. W. , Pasley J. N. , Scheving L. E. , Halberg Franz
Published: February 2005

Lesions of the suprachiasmatic nuclei (SCN) have been reported to disrupt or abolish circadian rhythms of motor activity and body temperature as well as of several neuroendocrine functions. This study was undertaken to determine any effect the SCN may have on the prominent circadian rhythm characteristic of the mitotic index of the corneal epithelium. Singly caged adult mice of both sexes were fed ad libitum and standardized to 12 hours of light alternating with 12 hours of darkness. Animals were divided into experimental and control groups. Later they were killed in subgroups at the time intervals of 0800, 1200, 1000, 0000, 0400 hour. Mitotic counts were determined on both right and left corneas of all mice. The data were plotted separately for both groups and reflect colony variation. We conclude that major lesioning of the SCN or its efferent projections disturbed but did not abolish the rhythm. In animals with unilateral lesions of the SCN, the mitotic index was consistently lower in the ipsilateral cornea. The mitotic index for animals with lesions which missed the SCN or its efferent projections did not differ from controls. The nuclei appear to function as pace‐resetters and amplifiers of the rhythm studied.
Cyclic variations in the oviductal ciliated cells during the menstrual cycle and after estrogen treatment in the pig‐tailed monkey, Macaca nemestrina
Authors: Odor D. Louise , Gaddum‐Rosse Penelope , Rumery Ruth E. , Blandau Richard J.
Published: February 2005

The epithelium of the oviduct of the pig‐tailed monkey, Macaca nemestrina was studied (1) to determine whether quantitative changes in the number of ciliated, deciliated, reciliating and nonciliated cells occur during the menstrual cycle and under certain experimental conditions and (2) to describe the ultrastructure of the ciliated and ciliogenic cells. The mean percentage of ciliated cells decreased from 48.2 in the fimbriae and 48.3 in the ampullae in the postovulatory stage to 7.7 and 18.8, respectively in the late luteal phase; these changes are significant as determined by Duncan's multiple range test. In the early follicular phase 3.9% of the cells in the fimbriae and 11.2% in the ampullae are ciliated, and the number of ciliogenic (deciliated and reciliating) cells is the highest of any time in the cycle in both the fimbrial (6.3%)and ampullar (8.4%)epithelium. In contrast, although the percentage of ciliated cells in the isthmus varies from 44.4 in the preovulatory phase to 34.3 in the early follicular phase, the differences between the various times in the cycle are not significant. However, in the late luteal phase, the values for the fimbriae and ampullae are significantly different from that of the isthmi. Ciliated cells constitute less than 1% of both the fimbrial and ampullar epithelium 2 ¾ years after ovariectomy, but 16.7 in the isthmic tissue. In ovariectomized monkeys treated for 7 or 12 days with estradiol benzoate reciliation occurs, but to a significantly lesser extent in the fimbriae and ampullae than in the pre‐ or postovulatory animals; the degree of reciliation in the isthmus is not different from the values noted during the cycle. The ultrastructure of ciliated, deciliated and reciliating cells is described. Of much interest is the finding of cytoplasmic protrusions containing variable numbers of ciliary axonemal complexes. It is postulated that such internalization of ciliary micotubules may represent one way in which deciliation may be accomplished.
Phenobarbital‐induced alterations of the rat adrenal cortex
Authors: Penney David P. , Averill Kathy T.
Published: February 2005

To determine the morpholic changes in adrenocortices induced by chronic phenobarbital therapy, the male rats were orally administered the drug daily for varying periods up to three months. Fine structural changes attributable to the drug included mitochondrial pleomorphism and cavitation, loss of cholesterol ester clefts, reorganization of intracellular lipid, hypertrophy of the agranular endoplasmic reticulum and a juxtapositioning of the agranular endoplasmic reticulum, mitochondria and lipid droplets—all suggestive of an actively secreting cortex. The digitonin‐glutaraldehyde reaction suggested an active translocation of free cholesterol from lipid droplets to the mitochondria and agranular endoplasmic reticulum following phenobarbital treatment. Phenobarbital appears to stimulate corticosteroidogenesis due in large part to enhanced hepatic corticoid metabolizing enzymes.
Ultrastructure of the chondrocytes and extracellular matrix of the Swarm rat chondrosarcoma
Authors: Hascall Gretchen K.
Published: February 2005

The Swarm chondrosarcoma, a transplantable tumor maintained in rats, has a structure similar to hyaline cartilage. The extracellular matrix contains narrow, banded collagen fibrils and proteoglycan matrix granules. The cells are filled with organelles typically involved in synthesis and secretion, including an extensive rough endoplasmic reticulum with dilated cisternae, a large Golgi apparatus dispersed throughout the cell, and secretory vacuoles which fill directly from Golgi saccules. There is only one class of secretory vacuoles, suggesting that the secretory products, collagen and proteoglycan, are packaged and secreted together. The cells also contain unusual endoplasmic reticulum, many coated vesicles and multivesicular bodies, and abnormal mitochondria. The large amount of tissue available from the tumor, and its characterization biochemically (Choi et al., '71; Oegema et al., '75) and morphologically as cartilage, make the tumor valuable as a model tissue for studies of synthesis and secretion of extracellular matrix materials.
Distribution of iron in the gastrointestinal tract of the common vampire bat: Evidence for macrophage‐linked iron clearance
Authors: Morton David , Wimsatt William A.
Published: February 2005

Iron in the tissues of the digestive tract of the common vampire bat (Desmodus rotundus) has been studied using histochemical, electron microscopic, and autoradiographic methods. This animal is an obligate sanguivore and has a daily intake of dietary iron 800 times that of man. The amount and distribution of tissue iron is not affected by either a single blood meal or starvation but does reflect the degree of siderosis of each animal's liver and spleen. By 7 days after the injection of a trace amount of 55Fe into the peritoneal cavity, labelled siderotic macrophages are present both on the serosa and within the walls of the stomach and intestine. In the lower intestine, such cells can be derived from the germinal centers of Peyer's patches. Siderotic macrophages are often situated in the lamina propria under areas of siderotic epithelium. Label is also present in the apical cytoplasm of mucosal epithelial cells, a region of abundant siderosomes. The ultrastructure of these organelles is extremely variable. Accumulations of membranous whorls and stacks, “stippled bodies,” ferritin molecules, and larger “ferruginous” complexes are bounded by one or a number of membranes. Iron is excreted when these epithelial cells are desquamated into the gut lumen. Similar Prussian blue‐positive granules are present in the feces. Unlike other glandular cells, the parietal cells of the fundic caecum are siderotic. Their cytoplasm contains abundant siderosomes and ferritin with accumulations of amembranous ferritin bodies in the intracellular canalicular spaces. Prussian blue‐positive granules are present in the lumens of fundic glands.
Effects of orchidectomy on the adrenal macrophage system
Authors: Maglhães Manuel M. , Magalhães Maria C.
Published: February 2005

Macrophages of the adrenal cortex were studied in normal and orchidectomized rats. In normal rats, few macrophages with numerous cytoplasmic granules were observed, mainly in the zona reticularis. Granules were limited by a single membrane and contained either a finely granular dense matrix or heterogeneous materials made up of electron‐lucent parts, dark granular and membranous areas. An aminotriazole‐resistant peroxidatic activity was confined to the dense granules. In orchidectomized rats, the number of macrophages was markedly increased, and the cells were concentrated at the border between the zonae fasciculata and reticularis and disseminated throughout the zona reticularis. Lysosomes were more numerous in each macrophage, and those of heterogeneous matrix were larger and their contents were more complex than in normal rats. These results show that orchidectomy stimulates the adrenal macrophage system.
Differential changes in cartilage cell proliferation and cell density in the rat craniofacial complex during secondary palate development
Authors: Diewert Virginia M.
Published: February 2005

During mammalian secondary palate formation sagittal growth of the lower face has been shown to be more rapid than that of the upper face, and the tongue and mandible extend beneath the primary palate. In order to identify factors contributing to this differential growth pattern, cellular and morphologic growth of the major cartilages of the upper and lower facial regions were studied in radioautographic sections labeled with tritiated thymidine. Evaluation of cell‐density recordings, labeling indices, and structural dimensions revealed significant differences between Meckel's cartilage in the lower face, and the nasal cartilage and anterior cranial base cartilage in the upper face. After formation of the precartilaginous blastema, labeling indices were high in Meckel's cartilage (20–30%), but very low in the nasal cartilage and the anterior cranial base (0–2%). During secondary palate formation of the volume of Meckel's cartilage increased more rapidly than the other cartilages and its growth was primarily in the sagittal direction. Between days 15 and 17, the increase in the length of Meckel's cartilage (165%) was approximately twice as great as the increase in the combined length of the nasal cartilage and the anterior cranial base (77%). During this period induction of cleft palate with some teratogens has been shown to severely retard growth of Meckel's cartilage and produce mandibular retrognathia that contributes to delayed elevation of the palatal shelves. Therefore, extensive cell proliferation in Meckel's cartilage, during a period of limited proliferation in other craniofacial cartilages, appears to contribute to its rapid growth and its differential sensitivity to growth inhibition.
Secondary palatal development in the New Zealand white rabbit: A scanning electron microscopic study
Authors: Meller Samuel M. , De Paola Dominick P. , Barton Lorraine H. , Mandella Rosemary D.
Published: February 2005

Examination of surface topography in prefusion stages of secondary palatal development in rabbit embryos reveals a sequence of alterations in the surface cells of the epithelium along the medial margins of the palatal processes. A progressive increase in cellular protrusions resembling lamellipodia and filopodia, as well as cellular necrosis, is observed in those areas that undergo fusion. The changes precede fusion and are restricted to fusion sites. Prior to and at the time of epithelial contact between palatal processes, many long slender cellular protrusions are seen bridging the gap between the approximating tissues. The localization of the epithelial alterations and the appearance of similar cellular morphology in other embryonic epithelial fusion events strongly suggest: either an active role of the epithelial cells in the fusion of the secondary palate, or some common fundamental biochemical events that may facilitate or are responsible for the initial adhesion of such tissues.
Intramembrane events accompanying junction formation in a liver cell line
Authors: Montesano Roberto
Published: February 2005

To study intramembrane events leading to the establishment of intercellular junctions between epithelial cells in vitro, we examined monolayer cultures of a rat liver cell line by an in situ freeze‐fracturing technique (Pauli et al., J. Cell Biol., 72:763, 1977). Our observations indicate that an early step of junction formation between liver cells consists of the differentiation of a particle‐poor membrane stretch showing a honeycomb pattern of shallow P‐face depressions or E‐face bulges (“formation band”). This change in membrane organization precedes and accompanies the subsequent aggregation of junctional particles. The latter process results in the formation of irregular particle islands with peripheral branchings which tend to encompass the depressions in the membrane. The linear branchings grow and interconnect in a network of beaded strands, which gradually transform into smooth tight junctional fibrils, as previously described in fetal liver in vivo (Montesano et al., J. Cell Biol., 67:310, 1975), while the particle islands assume the typical configuration of mature gap junctions. Formation bands are particularly prominent between liver cells grown in the presence of hydrocortisone (5 μg/ml) in the culture medium.
Microtubule and microfilament populations of cell processes in the dental pulp
Authors: Holland G. R.
Published: February 2005

An attempt has been made to characterize the nature of the unidentified cell processes participating in gap junctions in the odontoblast layer. In peripheral and pulpal nerves, there is a strong relationship between axon caliber and microfilament and microtubule populations. This characteristic, together with the ratio of microtubules to microfilaments, has been measured and compared for four types of cell processes found in the dental pulp, including those participating in gap junctions. The processes taking part in the gap junctions cannot be distinguished from pulpal axons on the basis of microtubule‐to‐microfilament ratio nor on the relationship between microtubule and microfilament population and process caliber. While these findings do not prove that the “gap members” are nerve fibers, it does support the hypothesis that the processes taking part in gap junctions in the peripheral dental pulp are nerve fibers.
The renal cortical lymphatic system in dogs with unimpeded lymph and urine flow
Authors: O'Morchoe Charles C. C. , Albertine Kurt H.
Published: February 2005

The distribution and extent of the lymphatic circulation in the renal cortex was analyzed in three dogs under conditions of unimpeded lymph and urine flow. The kidneys were drip fixed with acrolein in vivo, and cortical tissue strips were prepared for light and electron microscopic examination. Analysis of 90 tissue strips revealed 38 cortical lymphatics, one third of which were intralobular in position. The intralobular lymphatic capillaries were related primarily to tubules, afferent arterioles, or renal corpuscles. The remainder of the lymphatics were located in interlobular connective tissue areas in association with the interlobular blood vessels. Interlobular lymphatics had a surface area twice that of intralobular vessels. Stereological analysis was used to estimate the volume density of the components of the renal cortex. The volume density of lymphatics was found to be 0.0014, but because of the relative infrequency of lymphatics, this value was considered to be approximate. The volume density data for non‐lymphatic renal components were found to be in close agreement with published data. From these volume density values it was concluded that the volume of cortical lymph in a functioning dog kidney is equivalent to about 1% of the volume of blood in the cortical peritubular capillaries.
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

The 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

Lamellar 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

In 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

It 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

Atrial 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

Cat 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

The 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

Blocks 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

Lamprey, 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

Desmosomes 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

Diagrams 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

Protein 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

The 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

The 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

The 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.
An electron microscopic study of the cardiac innervation in larval lamprey
Authors: Nakao Taisuke , Suzuki Satoru , Saito Mitsuo
Published: February 2005

Larval lampreys (Lampetra japonica) 13 and 21 mm in body length were examined by serial section electron microscopy and it was found that the young 13‐mm larvae which was 26 days old had no nerves to, and in, the heart. However, the heart of 21‐mm larval lampreys had two sets of nerve fibers entering the heart. One of the nerve fibers entered the heart via the porta venosa, ran along the vena jugularis impar, and ended in the sinus venosus. The other nerve entered with the porta arteriosa and terminated in the proximal region of the bulbus cordis. Two characteristic types of nerve endings were observed. One type of nerve ending contained numerous, small, clear vesicles about 40 nm in diameter. These endings were found only in the walls of the vena jugularis impar and the sinus venosus. The second type of ending characteristically contained distinctive large‐cored vesicles 60–130 nm in diameter mixed with numerous small, clear vesicles. These endings were present in the walls of the vena jugularis impar, the sinus venosus, and the bulbus cordis. It should be emphasized that the bulbus contained only the second type of nerve ending. The nerves in the heart were confined to specific regions and those from the two sources remained separate. Furthermore, the atrium, ventricle, ducts of Cuvier, and hepatic veins were completely devoid of nerves. There were no ganglion cells in any region of the heart.