bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural modifications of lutein cell gap junctions during pregnancy in the rat and the mouse
Authors: Albertini David F. , Anderson Everett 
Published: February 2005

AbstractBy use of lanthanum tracer and freeze‐fracture procedures it was found that granulosa‐lutein cells of the pregnant mouse and rat ovaries are connected by gap junctions and septate‐like zones of contact. Lutein cell gap junctions enlarge and become partially internalized by the end of the first week of gestation. Expansion of the gap junction domain appears to be due initially to intercalation of particles along borders of small gap junctions devoid of smaller non‐junctional particles. The number of gap junction lined processes appearing at the cell border increases concomitantly with hypertrophy of the lutein cell during the second week of pregnancy. Strands of particulate or grooved membrane emanate from the margin of larger gap junctions undergoing interiorization. Most large gap junctions are intimately associated with elements of the smooth endoplasmic reticulum. Spherical gap junctional profiles assume a deeper location in the lutein cell and may form concentric arrays by term while true surface gap junctions appear to fragment in the post‐partum corpus luteum. The modifications observed are interpreted with respect to biogenesis of the gap junction and the hormonal control of lutein cell function.
The wall structure of the arteries in the corpora cavernosa penis of rabbits; light and electron microscopy
Authors: Fujimoto Sunao , Takeshige Yoshio 
Published: February 2005

AbstractWall structures of the arteries in the corpora cavernosa penis were observed in rabbits. The deep (central) arteries in the proximal part of the penis have five or more independent ridges of the wall which are formed by the internal layer of the media consisting of almost longitudinal muscle cell layers. Electron microscopy of these regions revealed that the endothelial cells are connected to each other by many maculae and zonulae adherentes, and that smooth muscle cells of the media are separated from one another by a wide intercellular space embedding abundant collagenous fibers.The epithelioid cells constituting the media of the helicine branches of the deep artery vary in their fine structure from close resemblance to muscle cells, to cells with easily identified special features. Frankly epithelioid cells have few scattered cytoplasmic filaments of a single type, 60–90 Å in diameter, abundant ribosomes, active Golgi, and other features different from the typical smooth muscle cells. There is no suggestion that these epithelioid cells are either degenerative or undifferentiated forms of smooth muscle cells, as postulated by light microscopists. Transitions froms muscle to epithelioid cells are consistent with, but not proved by, our data.
Spatial distribution of mitosis in mouse epidermis
Authors: Mackenzie Ian C. 
Published: February 2005

AbstractThe cells of the upper strata of mammalian epidermis are flattened and aligned to form regular columnar units. It has been suggested that the position of the smaller underlying basal cells is related to the overlying cell columns. Examination of the position of metaphase figures in sheets of mouse epidermis indicated that mitosis occurs principally in cells lying just within the periphery of the cell columns but that there is no alignment of interphase basal cells within the columnar peripheries which could account for this position of mitosis.
Permeability barriers to cytochrome‐c in nerves of adult and immature rats
Authors: Malmgren Leslie T. , Brink John J. 
Published: February 2005

AbstractNerves in the tongues of adult and immature rats were examined with respect to their permeability to exogenous cytochrome‐c (mol wt 12,000) injected into the tongue. The distribution of cytochrome‐c was determined in cryostat sections on the basis of the peroxidase activity of this protein. Nerves of 14‐day‐old rats were permeable to injected cytochrome‐c. The larger nerves of older animals showed only localized accumulations of cytochrome‐c reaction product both between and within axons adjacent to endoneurial blood vessels. Reaction product was not found, however, in association with blood vessels penetrating nerves of the tongue that were not within the limits of tracer spread. In the smallest nerve branches, thin linear strands of reaction product filled the interstices between the nerve fibers.
Cyclicity in tumescence of the perineal labia of female lowland gorillas
Authors: Nadler Ronald D. 
Published: February 2005

AbstractThe first group norms on the periodic occurrence of tumescence in the perineal labia of female lowland gorillas were obtained in 9 captive subjects. Individual mean cycle lengths for 8 adult females in 2 experiments ranged from 25.9–36.3 days with overall means of 31.1 and 32.5 days. The one subadult female had a mean cycle length of 40.7 days. The median and modal duration of maximal labial tumescence were 1.8 and 1 day, respectively. Data from 3 animals on which menses were recorded during 6 cycles yielded relatively consistent postswelling phase durations of 8–11 days and durations of menstruation of 1–2 days. The data from 2 conceptions of 1 female suggested that time of ovulation was closely associated with the day of detumescence. These data are discussed in terms of certain differences as well as similarities which exist between the gorilla and its closest relative, the chimpanzee. The contribution of these data to the area of comparative reproduction is enhanced because of the significant taxonomic affiliations of the gorilla species.
Substructure in rod photoreceptor membranes
Authors: Nir Izhak , Pease Daniel C. 
Published: February 2005

AbstractFrog retinae, fixed only in buffered glutaraldehyde, were embedded for sectioning in glutaraldehyde polymerized with urea. In suitably thin sections globular substructures were seen in negative contrast after ionic staining with uranyl acetate and lead citrate, or after staining with neutralized phosphotungstic acid. Efforts to extract at least some of the lipid from sections before ionic staining enhanced the visualization of the “globules.” Exposure to KMnO4 solution, used as an oxidative section stain, also outlined globular substructure in negative contrast, but with the additional feature that positively stained surface “leaflets” associated with the aqueous compartment were well defined. Staining sections with OsO4 vapor resulted in positively stained membranes, but without any evident substructure. However, when sections which previously had been exposed to OsO4 vapor were secondarily stained with uranyl acetate and/or lead citrate, positively stained globular substructures then were revealed.The globular substructures always were centered in the hydrophobic core region of the disc membranes, and symmetrically spanned the full thickness of this layer. The diameter of individual particles approximated 50–55 Å. Reasons are presented for the supposition that the evident globules incorporate at least hydrophobic components of rhodopsin molecules. Findings are discussed in relation to various models of disc membrane organization that have been proposed in recent years.
A smooth muscle plexus associated with the aqueous outflow pathway of the rabbit eye
Authors: Knepper Paul A. , Farbman Albert I. , Bondareff William 
Published: February 2005

AbstractSmooth muscle cells were demonstrated adjacent to the aqueous outflow pathway in rabbit eyes. The cells were arranged as a discontinuous band, one to three layers thick and extended from the termination of Descemet's membrane to the ciliary body. Most of the cells were oriented with their long axes at right angles to the aqueous plexus, but many were arranged in a direction parallel to the plexus. The organization of the cells suggests that their contraction would exert a bi‐directional force, and therefore, affect aqueous outflow resistance.
Ultrastructure of the developing fetal hepatocyte of Macaca arctoides: A proposed model for studies of fetal drug metabolism
Authors: Quattropani Steven L. , Stenger Vincent G. , Dvorchik Barry H. 
Published: February 2005

AbstractThe ultrastructure of the hepatocyte of the fetal stumptail monkey was examined with the aim of defining a possible model for studies of fetal drug metabolism. Hepatocytes from fetuses of 80 and 160 days gestation, as well as from one animal one week of postnatal age, were examined and compared to human fetal hepatocytes at 12 and 16 weeks gestation. Marked variation was observed in the amount of lipid and the distribution of organelles within the cytoplasm of the hepatocyte in the monkey population. These differences were attributed to genetic variation. Two changes were seen which correlated with developmental age. The amount of hemopoietic tissue decreased and the amount of smooth endoplasmic reticulum increased as the animal matured. The problems of genetic variation and the relative number of hepatocytes at different stages of development were discussed relative to the use of this animal as a model for fetal durg metabolism studies. Attention to both of these problems is considered necessary for the interpretation of biochemical data in future studies.
Regeneration of single skeletal muscle fibers in vitro
Authors: Bischoff Richard 
Published: February 2005

AbstractA culture system utilizing single skeletal muscle fibers from adult rats was developed to study the origin and behavior of mononucleated myoblasts during muscle regeneration. The single fibers are removed manually from the leg and thigh muscles of 300–400 gm rats and maintained in vitro embedded in a fibrin clot overlain with culture medium. Regenerative events were monitored by continuous observation of the cultured fibers. During the first few hours in vitro the fibers undergo degenerative changes including the formation of myofibrillar contraction clots and pyknosis of myonuclei. The endomysial tube (basement lamina) remains intact along the entire length of the fiber and forms transparent chambers bridging the contraction clots. Single fibers are free of endomysial cells and display no cellular outgrowth in culture, except at the cut ends. In contrast, a rich outgrowth of endomysial connective tissue cells is found with bundles consisting of two or more fibers. Isolated mononucleated cells, presumed to be muscle satellite cells, are present within the endomysial tube of single fibers at the onset of the culture period. There is no evidence that myonuclei contribute to the formation of mononucleated cells. The satellite cells enlarge and begin to proliferate during the second day in vitro to form clones of presumptive myoblasts within the endomysial tube. The early clones have a cell doubling time of about 22 hours and exhibit mitotic synchrony. After 5–7 days in vitro the satellite cell progeny begin to fuse to from multinucleated myotubes within the endomysial tube of the original fiber. The myotubes display spontaneous contractile activity and may extend throughout the length of the endomysial tube.
Early embryology and implantation in the california leaf‐nosed bat, Macrotus californicus
Authors: Bleier William J. 
Published: February 2005

AbstractFemale reproductive tracts from 84 bats were examined by light and/or electron microscopy to observe early embryology and implantation in Macrotus. The earliest pregnancy was observed in October and by the end of October all bats were pregnant. Implantation had begun in most specimens from late October. In late November females were carrying implanted blastocysts in which differentiation of endoderm was noted. Reichert's membrane was first observed in November.In early December the trophoblast had begun to differentiate into cytotrophoblast and syncytiotrophoblast and by the end of January this differentiation was most evident. Reichert's membrane persisted until late January. Endoderm in the January sample completely surrounded the yolk sac cavity.By late February the embryos were at the embryonic disc stage and had differentiated mesoderm. The uterine‐fetal relationship was complex and an early placenta was recognized.In late March the embryos spanned a range of development from neural plate to limb‐bud stages. Parturition occurred in June.This lengthy gestation period is characterized by an embryonic diapause of approximately four and one‐half months. The roles of food supply and/or temperature in controlling this growth rate and the evolutionary implications of this development are discussed.
Correspondence of silver nitrate staining patterns in decalcified bone with the microradiographic image
Authors: Tappen Neil C. , Simmons David J. 
Published: February 2005

AbstractA procedure for differential staining of decalcified bone with silver nitrate showed major histological features which appeared to correspond closely to microradiographic images. The extent to which this is actually the case was investigated directly by preparing microradiographs of ground sections of baboon and dog radii and then decalcifying and staining the same sections. The many detailed similarities indicate that this staining procedure is a useful adjunct to microradiography. Thus, poorly mineralized osteons or layers of circumferential lamellae are darker stained by silver nitrate, and the variably mineralized layers of circumferential lamellae are closely duplicated by light and dark bands in the stained sections. These similarities imply that there is a relationship between the mineral density of bone and some condition of the organic matrix which is probably related to maturation changes in the collagen.
Fine structure of mammalian renal cilia
Authors: Webber W. A. , Lee J. 
Published: February 2005

AbstractStudies were carried out, using transmission electron microscopy, of the cilia of the nephrons of rat and human kidneys. Cilia were observed in the parietal layer of Bowman's capsule, in the proximal tubule, the distal tubule, including the macula densa, and the collecting duct. They had a number of characteristic features, including the presence of a centriole adjacent to the basal body, long, slender cross‐striated rootlets, and a typically organized basal body. The shaft of the cilia differed from the typical 9 + 2 pattern of organization. Near the base of the cilia the pattern was 9 + 0. In the middle portion, one or more of the peripheral doublets had been displaced centrally to give an 8 + 1 or a 7 + 2 pattern, while towards the tip the pattern became more irregular and the doublets were reduced to single microtubules. We have hypothesized that these cilia may be vestigial. They may, if motile, have some minor stirring function, or they may play a sensory role, as has been postulated for similarly structured cilia in other sites.
Structure of rat bile canaliculi as revealed by scanning electron microscopy
Authors: Motta Pietro , Fumagalli Guido 
Published: February 2005

AbstractBile canaliculi in the rat liver have been studied by scanning electron microscopy. They appear as half tubules carved out of the hepatocytes' surface. In several cases the bile channel bifurcates to form two or three long branches running on the same face of the cell. Therefore, by SEM it seems obvious that the same side of an hepatocyte may be used for bounding two or more bile canaliculi.Some bile canaliculi display a flexuous course and show lateral sacculations. Some of them are large and apparently similar to the short lateral branches of the bile canaliculus; others are smaller and arise obliquely from the subjacent cortical areas of the hepatocyte cytoplasm. These latter structures are best observed in stereo‐views in which they appear as narrow intracellular projections bordered with a few microvilli, actually opening into the lumen of the bile canaliculus. The SEM results suggest that these sacculations probably correspond to short intracellular branches of the bile canaliculi.Zones of minimal distance (0.1 μ) between the space of Disse and the bile channel have been frequently observed. They are actually the zones where the intercellular clefts arising from the subendothelial space of Disse come into closest contact with the bile canaliculus and might serve as sites of simple diffusion of substances.
The “imaged‐desmosome”: A component of intercalated discs in embryonic guinea pig myocardium
Authors: Forbes M. S. , Sperelakis N. 
Published: February 2005

AbstractA heretofore undescribed structural variation of the desmosomes of the intercalated disc is found in myocardial cells of the embryonic guinea pig. These desmosomes consist of the usual pair of opaque leaflets, each of the pair contributed by one of the apposed muscle cells. In addition, in the cytoplasm of one of the cells there appears a pair of linear densities (facsimile‐lines) parallel to the nearest desmosomal plaque and separated from it by a 60 nm space. The facsimile lines superficially resemble the desmosomal leaflets in length and thickness, thus forming a cytoplasmic “image” of the desmosome. These “imaged‐desmosomes” are found predominantly in the longitudinally‐running portions of the intercalated discs and are common in 7‐week embryos. Their incidence drops sharply by eight weeks of gestation, and they are virtually absent from the heart of the newborn animal. Often tubules of the sarcoplasmic reticulum (SR) are found in apposition to the facsimile‐lines; thus it appears that association of SR tubules with desmosomes is responsible for the formation of imaged‐desmosomes.
The effect of strontium, cobalt and fluoride on rat incisor enamel formation
Authors: Neiman Abraham , Eisenmann Dale R. 
Published: February 2005

AbstractThis investigation examined ultrastructurally the entire period of development of alterations in formative ameloblasts and the enamel which they produce following injection with fluoride, strontium, and cobalt ions. Rats injected with these ions were sacrificed at intervals of 1, 2, 4, 8, 16, 24 and 48 hours to elucidate the sequence and detail of cytologic and cell product alterations which occur. Undecalcified sections of rat incisor teeth were studied using electron microscopy and microradiography. All three ions initially produced disturbances in cell morphology and enamel formation consisting of dark globules, vacuoles, and pooling of stippled material on the enamel surface. While a period of decreased crystal formation occurred after injection with all three ions, only cobalt responses included a period of apparently complete absence of crystal formation. The hypermineralized layers occurring in the altered enamel are attributed to changes in the rate of enamel matrix formation and duration of its exposure to tissue fluids. Morphologic changes in Tomes' process were observed at the time of formation of abnormal enamel following injection of all three ions. These observations are compared with previous studies of altered enamel formation and analyzed with the goal of learning more about the mechanisms of amelogenesis.
Surface epithelium of the fetal guinea‐pig ovary: A light and electron microscopic study
Authors: Jeppesen Th. 
Published: February 2005

AbstractThe surface epithelium in fetal guinea‐pig ovaries was examined from the time of early sexual differentiation, about 34 days, until approximately ten days before birth.At day 34 the epithelium varied greatly in apperance as seen in the light microscope and possessed a superficial layer of flattened or cuboidal cells. By day 58 the epithelium had changed into one layer of regularly arranged columnar cells. During the same period the number of germinal cells decreased. Connections between the germinal cords and the surface epithelium were observed from day 34, being especially numerous and broad at days 34 and 42 and decreasing in number and size from day 46 onwards. The basement membrane beneath the epithelium gradually increased in thickness.In the electron microscope two types of somatic cells could be distinguished. One type formed a superficial single layer connected by junctional complexes and exhibited intracellular bundles of 60 Å microfilaments running straight through the apical part of the cell, attached to junctional complexes on either side. These bundles were found frequently between days 34 and 42, but were rarely seen after the forty‐sixth day. Microvillous projections into the coelomic cavity were especially numerous from day 34 to day 46.The other type of somatic cells lay in close proximity to the germinal cells: microfilaments or junctional complexes were not observed.The subepithelial basement lamina was continous with that surrounding the connections and the germinal cords.
Cellular mechanisms involved in cyclic stromal renewal of the uterus. I. The opossum, didelphis virginiana
Authors: Padykula Helen A. , Taylor J. Mary 
Published: February 2005

AbstractAt the close of a uterine cycle, the remodelling of the endometrial stroma of the North American opossum involves removal of extracellular material by macrophages. This study provides cytochemical and ultrastructural evidence which indicates that the laden macrophages are eliminated from the endometrium through emigration across the glandular and luminal epithelia. During diestrus or the early postpartum period, the abundant uterine glands relinquish their secretory function to acquire a transient function in the transportation of emigrating stromal cells.During the first three postpartum days endometrial regression in the stroma is marked by sudden appearance of monocytes, macrophages, lymphocytes, and plasma cells. Ultrastructural and cytochemical evidence indicates that the macrophages engulf the extracellular macromolecular material which, in the opossum, consists primarily of ground substance. Macrophages filled with ingested extracellular material aggregate beneath the glandular and luminal epithelia, where they acquire an extracellular coat that resembles the material of the basal lamina elsewhere. A fibroblast‐like cell closely invests the macrophage at the time the extracellular material appears. Simultaneously, the secretory glandular epithelium is being converted to a highly ciliated one. Macrophages, often accompanied by lymphocytes, acquire intraepithelial positions in the glands. From here these stromal cells gain entrance to the glandular lumens. At this time the luminal contents are rich in acid phosphatase activity which most likely reflects the high lysosomal content of the emigrating macrophages. Evidence suggests that these intraluminal macrophages and lymphocytes are swept, by the recently differentiated ciliary lining, toward the glandular orifices and into the uterine cavity. It is hypothesized that this cyclic appearance and transepithelial elimination of macrophages is a cellular mechanism for removing large amounts of extracellular material without disruption of the endometrium.