bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of the aging human testis
Authors: Paniagua Ricardo , Nistal Manuel , Sáez Francisco J. , Fraile Benito 
Published: February 2005

AbstractThe ultrastructure of the progressive testicular involution with advancing age in men is reviewed. There is no definite age at which testicular involution begins, and the onset and severity of testicular lesions are subjected to pronounced individual variations. Hormone studies also indicate great individual variations, and subtle changes in both the testis and the pituitary develop progressively with age. Testicular size, sperm quality, and numbers of all germ cell types, Sertoli cells, and Ley dig cells decrease with age. The volume occupied by the seminiferous tubules decreases, whereas that occupied by the testicular interstitium remains constant. The most frequent histological pattern of the aging testis is a mosaic of different seminiferous tubule lesions, varying from tubules with complete, although reduced, spermatogenesis, to completely sclerosed tubules. The tubules with complete spermatogenesis may show numerous morphological abnormalities in the germ cells, including multinucleation. Abnormal germ cells degenerate causing Sertoli cell vacuolation. These vacuoles correspond to dilations of the extracellular spaces resulting from the premature exfoliation of germ cells. Degenerating cells that are phagocytosed by the Sertoli cells give rise to an accumulation of lipid droplets in the Sertoli cell cytoplasm. The loss of germ cells begins with the spermatids, but progressively affects the earlier germ cell types, and tubules with maturation arrest at the level of the spermatocytes or spermatogonia are observed. The Sertoli cells show morphological abnormalities such as dedifferentiation, mitochondrial metaplasia, and multinucleation. Germ cell loss is associated with thickening of the tunica propria. When all seminiferous epithelial cells have disappeared, only an intensely collagenized tunica propria with myoid cells remains (sclerosed tubules). The Ley dig cells progressively dedifferentiate with a decrease in the quantity of both smooth endoplasmic reticulum and mitochondria, together with an accumulation of lipid droplets, crystalline inclusions, and residual bodies, and formation of multinucleate cells. The development of tubular involution with age is similar to that observed after exprimental ischemia, suggesting that vascular lesions may play an important role in age‐related testicular atrophy.
Immunogold electron microscopic localization of antigenic sites in the outer dense fiber region of rat sperm tail obtained by using antisera to two Sertoli cell secretory proteins
Authors: Kierszenbaum Abraham L. , Ueda Hiroshi , Tres Laura L. 
Published: February 2005

AbstractPolyclonal antisera raised against polypeptide components of two rat Sertoli cell secretory proteins, designated protein S70 and S45–S35 heterodimeric protein on the basis of cell origin and estimated molecular weight, were used to identify antigenic sites in (1) rat testis, () cultured Sertoli cells, (3) developing spermatids (collected from spermatogenic stage‐specific seminiferous tubular segments), and (4) epididymal sperm. Indirect immunofluorescence, immunoper‐oxidase, and immunogold electron microscopy (single and double labeling) were used. Immunocytochemical techniques have detected antigenic sites in (1) the cytoplasm of Sertoli cells in the intact seminiferous tubule and in culture in the form of a punctuate, granular‐like pattern, and (2) the acrosome (but not the Golgi region) and tail of developing spermatids and sperm. In developing spermatids, the principal piece of the tail displays a characteristic apical‐to‐distal immunoreactive banding pattern that correlates both temporally and spatially with the reported multistep assembly of outer dense fibers along the axoneme. The immunoreactivity of the acrosome, connecting piece, and outer dense fibers of the sperm tail was confirmed by immunogold electron microscopy. A precise identification of the component(s) of the outer dense fiber region responsible for the antigenic homology with Sertoli cell secretory proteins is under investigation.
Cryofixation of vascular endothelium
Authors: Wagner Roger C. , Andrews S. Brian 
Published: February 2005

AbstractCryofixation refers to the immobilization of tissue components by the rapid removal of heat from the specimen, so that the structure is interred and stabilized in a natural embedding medium, namely, frozen (amorphous or microcrystalline) tissue water. Cryofixation is now often used as a complement to the more traditional fixation methods, especially when the cell structure is delicate or dynamic and may be inaccurately preserved by the slow selective action of chemical fixatives. Vascular endothelial cells are specialized for transcellular transport and for the regulation of blood flow and composition. The dynamic and labile subcellular organization of these cells, presumably reflecting these functional specializations, makes them ideal candidates for cryofixation.Several different types of endothelial cells were directly frozen at temperatures below 20 degrees Kelvin by pressing them against a liquid‐helium‐cooled block. These samples were subsequently processed for structural analysis by freeze‐substitution. Detailed rationales, designs, and protocols are described for both freezing and freeze‐substitution.Electron micrographs of cryofixed arterial and venous capillaries (rete mirabile of the American eel), iliac vein (rabbit), and cultured endothelium from the iliac vein (human) reveal that the organization of the characteristic intracellular membrane system of endothelial vesicles is qualitatively similar to that seen in chemically fixed endothelium, especially with regard to the interconnection of clusters of individual vesicles to form elaborate networks. The luminal and abluminal networks are not in communication, at least not in static images. Quantitatively, however, most directly frozen endothelial cells have far fewer vesicular profiles than comparable glutaraldehydefixed cells. The differences can be explained by presuming that the rapid action of cryofixation (approximately 1 msec) gives a more accurate picture of the vesicular network because it captures the transient structure of labile or dynamic membranes.
The endothelial vesicle system in cryofixed frog mesenteric capillaries analysed by ultrathin serial sectioning
Authors: Frøkjæer‐Jensen Jørgen 
Published: February 2005

AbstractConventional EM sections of chemically fixed capillary endothelial cells reveal numerous apparently free smooth plasmalemmal vesicles. However, the method of ultrathin (< 150 Å) serial sectioning has shown that the smooth vesicle profiles arise merely as a result of the EM thin sectioning of two sets of complex vesicular invaginations from the luminal and abluminal cell surfaces, which end blindly in the cytoplasm. While 50–70% of the total population of vesicular profiles appear to lack connections to the cell surface in conventional (500–700 Å thick) EM thin sections less than 1% truly free vesicles can be found by the ultrathin serial section analyses.In the present study it is examined whether similar conclusions apply to endothelial cells which were directly frozen by slam‐freezing and subsequently freeze‐substituted. The three‐dimensional organization of the plasmalemmal vesicular system was analyzed in four series of 19, 18, 13, and 10 ultrathin sections (approximately 110 Å thick) of capillaries from frog mesenteries quickly excised from decapitated frogs (Rana pipiens). None of 920 vesicular profiles (diameter 500–1,200 Å) which appeared free in individual thin sections of the series represented free vesicles; all profiles either communicated with other vesicles, the cell surface, or in rare cases turned out to be part of cytoplasmic tubular membrane structures. It is concluded that free smooth plasmalemmal vesicles are very rare in rapidly frozen as well as in directly fixed frog capillary endothelium.The volume density of profiles (13–15%), the proportion of apparently free vesicle profiles (70%), and interconnected profiles (20%) were similar to the picture previously found in single EM sections of frog mesenteric capillaries. No transendothelial channels were found in the four series of ultrathin sections of capillaries. However, continuities between the luminal and abluminal cell surfaces were seen in the endothelium of venules. Furthermore, in the ultrathin series of the capillaries, vesicular units belonging to the two sets of invaginations and cytoplasmic tubular membrane structures were in more cases found in very close contact—as fused to share one unit membrane. If this finding is representative for the in vivo situation, it may reflect that the vesicular system represents a highly dynamic system with possibilities for mixing of membranes, cellular traffic of lipid, membrane proteins, and receptors between internal compartments and the cell surfaces, as well as occasional exchange of macromolecules between blood and tissue through rare temporary connections between the two sets of surface invaginations, without actually moving vesicles.
Lectin and immunolabeling of microvascular endothelia
Authors: Milici Anthony J. , Porter Glyn A. 
Published: February 2005

AbstractA number of recently developed localization techniques are beginning to be applied in the study of endothelial cells and their structural components. In this article we will review a number of these cytochemical approaches as well as their advantages and disadvantages and their applications. The methods will be presented for processing tissues for either L.R. White embedding or semi‐thin and thin frozen sections followed by subsequent lectin and immunolabeling for fluorescence and electron microscopic examination. These techniques are easily applied in the localization of perfused exogenous proteins and of endogenous endothelial‐associated proteins. The results that can be obtained from such studies are presented and discussed.
Quick‐freeze, deep‐etch studies of endothelial components, with special reference to cytoskeletons and vesicle structures
Authors: Izumi Toshihiro , Shibata Yosaburo , Yamamoto Torao 
Published: February 2005

AbstractA three‐dimensional study of the ultrastructure of endothelial cells is helpful in understanding important endothelial functions such as vascular transport and cell permeability. For this purpose, in addition to serial sectioning electron microscopy and high‐voltage electron microscopy, the quick‐freeze, deep‐etching technique also enables us to analyze structures at the molecular level by its high resolution and is useful for three‐dimensional morphological studies.Some modifications on the conventional deep‐etching method were made in this study to reduce the undesirable aggregation of proteins and salts during etching. Using this technique, we examined the rat aortic endothelium, particularly the membrane structures and cytoskeletons.The luminal surface of the endothelium was covered with a fine filamentous coat, which was anchored to the plasma membrane. In the cytoplasm, actin filaments were prominent and were oriented randomly or in a parallel fashion near the plasma membrane. Of the vesicles seen in the endothelium, some had basket coats of clathrin, and others had striped coats on the cytoplasmic membrane surface. These surface structures of the vesicles suggest the transport mechanism of the vesicles in association with the fine filaments attached to the vesicles.
Grain boundary character distributions in Ni‐16Cr‐9Fe using selected area channeling patterns: Methodology and results
Authors: Crawford Douglas C. , Was Gary S. 
Published: February 2005

AbstractSelected area channeling patterns imaged on an SEM are digitized and displayed on the screen of a Macintosh computer, on which the user selects channeling bands that are measured to determine orientation. Grain boundary misorientations are found using the orientation information for pairs of grains adjacent at grain boundaries, and the boundaries are classified as low angle boundaries (LABs), coincident site lattice boundaries (CSLBs), or general boundaries (GHABs) based on the misorientation information. The technique was implemented to analyze the grain boundary character distributions (GBCDs) in Ni‐16Cr‐9Fe. The GBCDs of solution annealed material were similar to those expected in an aggregate of randomly oriented polycrystals. However, sequential thermomechanical treatments (5% tensile strain + 945°C:75 min + 2% tensile strain + 890°C:15 h + 3% tensile strain + 890°C:20 h or 9% compressive strain + 890°C:20 h + 9% compressive strain + 890°C:20 h + 3% compressive strain + 890°C:15 h) applied after the solution anneal lowered the proportions of GHABs in the GBCDs from 76–79% to 47–64%. The CSL‐enhanced GBCDs of both the tensile‐deformed samples and the compression‐deformed sample appear to have evolved mainly through impingement of twin and twin‐related boundaries during recrystallization; the CSL‐enhanced GBCD of a compression‐deformed sample appears to have been influenced by grain rotation processes to a greater degree than were the tensile‐deformed samples. The CSL boundaries in the CSL‐enhanced GBCDs were, in general, closer to the exact CSL misorientations than were those in the near‐random GBCDs of the solution annealed material. An analysis of the distribution of misorientation axes did not indicate any correlation between grain misorientation texture and GBCD evolution.
Microvascular architecture of the elastase emphysemic hamster lung
Authors: Hossler Fred E. , Douglas John E. , Verghese Abraham , Neal Larry 
Published: February 2005

AbstractVascular corrosion casts of normal and elastase‐induced emphysemic hamster lungs, prepared with a low viscosity resin mixture consisting of Mercox and Sevriton, were observed by scanning electron microscopy. Casts were quantitated by measuring vascular volume or determining non‐alveolar air space using confocal laser scanning microscopy. Normal lung casts were characterized by well‐organized fields of alveoli (about 70 μm in diameter) connected by distinct alveolar ducts. Emphysemic lung casts exhibited numerous bullae (often as large as 0.5 mm in diameter). The vasculature of the bullae indicated that they were formed by destruction of alveolar walls and subsequent coalescence of numerous alveolae. Remnants of alveolar walls, consisting of shallow ridges of capillaries, lined the bases of the bullae. Vascular volumes expressed as cast volume/total tissue volume were calculated at 20% and 12% for uninflated and inflated lungs, respectively, for both control and emphysemic lungs. Four months after elastase instillation, non‐alveolar air space of the emphysemic lungs was increased by 73% over controls. These observations indicate that elastase emphysema results, initially, in remodeling of the alveolar structure (bullae formation) and loss of surface area for gas exchange, rather than from extensive loss of vasculature. Vascular corrosion casting is a useful technique for monitoring emphysema both morphologically and quantitatively.
The third joint of the canine jaw
Authors: Scapino Robert P. 
Published: February 2005

AbstractThe dog mandible has three joints — two temporomandibular and one symphyseal joint. In studies of jaws and their mechanics usually only the temporomandibular joints are considered. The symphysis is consistently neglected and because of this, remarkable features of the temporomandibular joints have never been noted.The symphysis has special connective tissue arrangements and its own vascular and nerve supply. Along the anterosuperior part of the symphysis, a strip of fibrocartilage, and running more or less parallel to it, strong cruciate ligaments bind the symphyseal plates together. Small arteries run into the symphyseal joint and it is drained by an anastomosing venous plexus. The posterior, ligamentous, portion is laced with a profuse network of nerves.The temporomandibular joint is unusual in that its joint disc is powerfully anchored to the skull medially and to the outer pole of the mandibular condyle laterally. The temporomandibular joint disc thus acts as a ligament that halts lateral movement of the condyle just as the carnassial teeth are aligned for cutting function. As the mandible moves laterally, the space between the posterior ends of the symphyseal plates widens: at the same time it narrows anteriorly. The cruciate ligaments control this movement and stabilize the symphyseal joint by preventing direct lateral displacement of the symphyseal plates. The fibrocartilage cushions this movement and also mediates rotational movements about the longitudinal axis of the mandible when crushing molar teeth come into function.
The relation of amicronuclearity to stomatogenic activity during conjugation in several ciliates
Authors: Diller William F. 
Published: February 2005

AbstractEarly in conjugation, both in micronucleate and amicronucleate ciliates, the original oral structures degenerate and are quickly succeeded by new rudiments which may or may not attain functional competency. These changes were followed in matings of amicronucleate Oxytricha fallax and, in somewhat less detail, of amicronucleate Paramecium multimicronucleatum and P. trichium.In the ex‐conjugants of Oxytricha the new peristomes did not reach complete structural development: they bore a deficient number of adoral membranelles and lacked an undulating membrane along the right border. Numerous isolated pairs gave rise to ex‐conjugants, all of which died within a few days. Macronuclear changes in conjugation seemed normal.In P. multimicronucleatum most of the ex‐conjugants lacked a buccal cavity. Either the second generation oral apparatus had failed to develop or had disappeared quickly after it did arise. An occasional ex‐conjugant possessed an oral opening which could have been the persisting original buccal cavity, or a possible new one. Isolated pairs yielded 80–100% lethality. The discrepancy from 100% is explainable on the basis of precocious separation of a small number of pairs before their macronuclei had reached irreversible skein formation, as judged by stained specimens. The macronuclear changes were somewhat different from those of micronucleate conjugation.P. trichium amicronucleate conjugations were studied only from cases in mass cultures, all of which died out. Although most of the ex‐conjugants lacked buccal cavities, there was a higher percentage of individuals with mouths than was true for P. multimicronucleatum.
An autoradiographic study of RNA synthesis in isolated salivary glands of Drosophila hydei. II. Interferometric studies
Authors: Pollister Arthur W. 
Published: February 2005

AbstractInterferometric measurements were made on sections of salivary glands mounted in oils of refractive indices 1.410, 1.460, and 1.500, estimating optical path differences as fringe displacement with a Leitz double‐beam interferometer microscope. From these data the mean concentrations (in mg/cm2/micron) of 55 cells of three glands were computed as follows: karyoplasm, 0.027±0.0026; cytoplasm, 0.048 ± 0.0024; nucleolus, 0.066±0.0041. From these concentrations it was computed, according to Maurer and Primbsch (Exp. Cell Res., 33: 8–18) that the correction factors for four micron sections were: karyoplasm, 0.203; cytoplasm, 0.114; nucleolus, 0.083. The reciprocals of these fractions (5.0, 8.8, and 12.0) are the correction factors of Arnold (J. Morph., in press) by which measured silver grain densities on autoradiographs are multiplied to give corrected (i.e. potential) densities.
The development of the skull of Psammophis sibilans. II. The fully formed chondrocranium
Authors: Kamal A. M. , Hammouda H. G. 
Published: February 2005

AbstractThe fully formed chondrocranium of the Egyptian snake, Psammophis sibilans has been described in detail. The tectum synoticum is very broad and there is apparently no tectum posterius. The notochord is completely embedded in the occipital condyle. The connection between the condyle and the odontoid process persists to the fully formed stage. There is only one commissure, representing the anterior basicapsular commissure, connecting the auditory capsule to the basal plate. The fisura metotica is continuous postero‐dorsally with the fissura occipitocapsularis. The distal bent end of the shaft of the columella auris represents the processus dorsalis, and the nodule that separates from it and fuses with the quadrate is the intercalare. The interorbital septum, orbitosphenoid cartilages, basitrabecular processes and planum supraseptale are completely absent. The concha nasalis is of the simplified type, the active factor in its formation is the folding of the olfactory epithelium. The solum nasi is greatly reduced and comprises the floor of the cupola anterior, the composite lamina transversalis anterior, cartilago ectochoanalis, cartilago hypochoanalis and ectochonal plate. The branchial arches are completely absent. The pterygoquadrate is represented only by the quadrate cartilage. The ceratohyals are extremely long.
The development of the skull of Psammophis sibilans. III. The osteocranium of a late embryo
Authors: Kamal A. M. , Hammouda H. G. 
Published: February 2005

AbstractThe osteocranium of a late embryo of the Egyptian snake, Psammophis sibilans (age, 58 days; total body length, 190 mm) has been described. Attention was given to the relation of the different bones to the adjacent cartilages of the chondrocranium as well as to the topographical relation of the bones to each other in the late embryonic state. Several adjacent bones have not yet come in contact with each other. The membrane‐bones make their appearance shortly before any sign of ossification in the cartilaginous cranium. The maxillary, palatine and pterygoid premordia have a slight earlier appearance than the other bony premordia. The lacrymal, postfrontal, squamosal, jugal, quadratojugal and epipterygoid bones are completely absent. The laterosphenoid bone is never performed in cartilage. The whole columella auris is ossified.
The adult and larval morphology and life history of the entoproct Barentsia gracilis (M. Sars, 1835)
Authors: Mariscal Richard N. 
Published: February 2005

AbstractThe morphology of the entoproct Barentsia gracilis (M. Sars, 1835), has been studied primarily by routine light microscopy techniques supplemented with observations by electron microscopy. In general, the B. gracilis adult is similar in structure to other members of the Pedicellinidae. Differences noted include: the presence of conspicuous fibers, probably collagenous, which appear to reinforce the stalk‐ calyx connection, the presence of a distinct glandular‐ appearing area (also present in the larva) of unknown function, and the presence of two rows of latero‐ frontal cilia on the tentacles. The first detailed morphology of an entoproct larva is also presented and the striking similarity to the adult noted. Due to the confused state of Barentsia systematics, it was found that B. gracilis, B. geniculata, and B. benedeni may very well be the same animal. This is due to the great variability, apparently due to ecological factors, found in the key taxonomic characters such as stalk morphology. The feeding behavior of the adult is described and the larval feeding and rejection mechanism is reported for the first time. The larva, while still in the brood pouch, uses its ciliary girdle to remove food from the parent's food groove. The larval feeding current is generally similar to that of the adult, with modifications which are related to the lack of tentacles in the larva. The larva differs from the adult in having special ciliated rejection pathways for the removal of excess food particles.