bluuebunny/crossref_metadata_2025_split huggingface dataset:
The organization of actin filaments in human polymorphonuclear leukocytes
Authors: Ryder Mark I. , Weinreb Robert N. , Niederman Richard 
Published: February 2005

AbstractActin constitutes a major component of the cytoskeleton of human polymorphonuclear leukocytes (PMNs). In this study, we present a comprehensive view of the organization of actin in various PMN regions and functional states. Transmission electron microscopic observations were made on whole mount, migrating, and phagocytizing PMNs. Positive identification of actin filaments was made through S‐1 myosin subfragment labeling. In all PMNs studied, actin filaments were primarily organized as a three‐dimensional meshwork. The density of this meshwork was greatest within the cell cortex. At peripheral regions of nonpolarized (viz., no distinct head or tail region) and polarized PMNs, actin filaments organized into parallel bundles or overlapping arcs. These bundles or arcs were oriented either perpendicular or parallel to the cell periphery. At the base of the PMN, actin filaments converged upon dense, plaquelike condensations. This latter pattern of actin organization was also observed in some pseudopods at the cell front and in phagocytic processes engulfing bacteria. In areas of internalized bacteria, the surrounding actin appeared as a loose meshwork. Treatment of PMNs with the antiactin drug, cytochalasin B, revealed shearing of the peripheral actin meshwork, condensation of the meshwork around the nuclear region, and dissolution of the basal plaquelike condensations.
From bone lining cell to osteocyte—an SEM study
Authors: Menton D. N. , Simmons D. J. , Chang S.‐L. , Orr B. Y. 
Published: February 2005

AbstractWe describe the SEM appearance of the rat endosteal bone lining cell (BLC) population, and the sequence of morphological changes of these cells as they self‐incorporate into unmineralized bone matrix (osteoid), establish intercellular connections, and construct lacunae. The osteoblast/nascent osteocyte series was progressively unsheathed by gentle digestion of the osteoid with 0.25% collagenase. The osteoblasts which leave the polygonally packed BLC compartment rapidly develop numerous complexly branched processes that contact the processes elaborated by previous generations of maturing and mature osteocytes. As osteoblasts mature and approach the mineralization front, they appear to lose processes. The mature cells begin to form osteocyte lacunae by depositing an asymmetric perimeter of woven collagen fibrils, such that as the cells roof‐over, the lacunae appear as pocketlike constructions. The collagen fibrils on the perilacunar matrix are oriented in a tangential or circular pattern, while those in the more distal matrix are arranged in a parallel pattern. With the completion of a lacuna, its wall appears to mineralize quickly, for lacunae could be recognized only when they are forming.
New evidence for monozygotic twins in the mouse: Twinning initiated in the late blastocyst can account for mirror image asymmetries
Authors: Runner Meredith N. 
Published: February 2005

AbstractThe 11.5‐day twin mice reported here support one of the classically described mechanisms for mammalian monozygotic twinning: subdivision of the blastocyst inner cell mass at the stage of proamnion cavitation. This particular method for monozygotic twinning has the attraction of providing a hypothesis for mirror image translocation of asymmetric traits. Monozygotic twins in laboratory rodents at or near parturition have not been identified and only two prior descriptions, for 7.5‐ and 9.5‐day mouse embryos, have been found in the literature. Experimentally induced twins having identical heredity, i.e., clones, would enable study of heritable and environmental regulation of the components of discordance. A set of twin mouse embryos at 11.5 days of gestation within a common yolk sac, and with shared vitelline and allantoic circulations, provides direct evidence that monozygotic twin mice can survive rotation within the common yolk sac and suggests a reasonable probability that they can survive to term.
Density of arteriovenous anastomoses in some skin areas of the domestic fowl (gallus domesticus)
Authors: Midtgård Uffe 
Published: February 2005

AbstractThe vascularity and the density of arteriovenous anastomoses (AVAs) were studied in the skin of the domestic fowl by using vascular injections and histological sections. The density of AVAs and associated blood vessels were low in the wattles and in the thoracic skin (five to 23 AVAs per cm2 and five to 14 AVAs per cm2, respectively), whereas the eyelids were highly vascular and contained many AVAs (170‐172 AVAs per cm2). It is suggested that the blood vessels in the eyelids are important in the temperature regulation of the eye and that AVAs in the thoracic skin may contribute to the control of blood flow through the brood patch.
Morphometry of the functional and regressing corpus luteum of the guinea pig
Authors: Azmi Tengku I. , O'Shea Jeremy D. , Bruce Neville W. , Rodgers Raymond J. 
Published: February 2005

AbstractA morphometric study of functional and regressing corpora lutea (CL) of guinea pigs (n = 5 per day) was performed on days 9, 12, and 16 of the estrous cycle. On day 9 the functional CL contained ⋍ 750,000 cells, which included 565,200 ± 56,700 (S.D.) endothelial cells or pericytes and 137,300 ± 7,700 luteal cells. Between days 9 and 12 the only significant change suggesting the onset of regression was a reduction in vascular luminal surface area. During this time the number of luteal cells per CL increased to 204,400 ± 34,800 (P < .05), with an accompanying reduction in luteal cell volume from 19.8 ± 1.8 to 14.4 ± 2.4 pl/cell (P < .01). The increase in cell numbers was explicable by cell division, with mitotic indices of 0.83% and 0.97% on days 9 and 12, respectively. Luteal volume was unaltered. Between days 12 and 16, the mean volume of a single CL fell from 3.98 ± 0.2 to 1.42 ± 0.3 mm3 (P < .01) and luteal cell volume was reduced to 5.3 ± 1.1 pl/cell (P < .01). Between these 2 days the number of endothelial cells per CL fell from 539,900 ± 75,500 to 144,400 ± 63,300 (P < .01), with an accompanying reduction in vascular luminal surface area and in the volume occupied by vascular lumina. The total number of luteal cells per CL was not reduced significantly. It was concluded that luteal cell numbers in the guinea pig increase up to the time of onset of luteal regression, and that during regression up to day 16, shrinkage of luteal cells is the major cause of loss of luteal volume. During regression, endothelial cell loss occurs much more rapidly than loss of luteal cells.
Blood supply and drainage of the outer medulla of the rat kidney: Scanning electron microscopy of microvascular casts
Authors: Yamamoto Kazuhide , Wilson Douglas R. , Baumal Reuben 
Published: February 2005

AbstractBlood supply and drainage of the outer medulla of the rat kidney were studied by scanning electron microscopy of vascular casts, using both arterial (n = 10) and venous (n = 10) injections of resin. Both outer and inner stripes of the outer medulla were supplied through different arterial capillary networks arising from efferent arterioles and arterial (descending) vasa recta. In contrast to previous studies using silicone rubber and light microscopy, a rich arterial capillary network supplying the outer stripe was demonstrated. Capillaries in the outer stripe and outer part of the inner stripe drained into venous vasa recta between vascular the bundles, while capillaries in the inner part of the inner stripe drained into venous vasa recta within the bundles. The results indicate that each zone in the outer medulla is supplied through separate capillary networks. The demonstration of a rich capillary network in the outer stripe of the outer medulla suggests that the predilection of this zone for tubular necrosis with ischemic or toxic injury is not related to a sparse capillary blood supply.
The influence of the hair cycle on the thickness of mouse skin
Authors: Hansen L. S. , Coggle J. E. , Wells J. , Charles M. W. 
Published: February 2005

AbstractThe data on mouse skin thickness reported here was prompted by the need to know the true postion of basal cells of the epidermis and hair follicles as these are important “cells at risk” for a variety of skin reactions including carcinogenesis following exposure to radiation. There is little reliable data in the literature and most previous reports have ignored the shrinkage of skin that occurs because of its natural elasticity.The values determined for mouse flank skin in telogen‐the resting phase of the hair cycle for the different skin layers‐are epidermis 10 μm, corium 250 μm, adipose layer 150 μm, and hair follicle depth 150 μm. Three days after chemical depilation which triggers the hair follicles into active cycle (anagen) the epidermis doubles in thickness, remains at this value for 7 days, and then gradually returns to telogen values by day 18. The corium and adipose layers also increase significantly to reach approximately 390 μm and approximately 260 μm, respectively, by day 10 and then return to control values from day 15 onward. The change in hair follicles depths are more dramatic with active follicle basal cells reaching approximately 450–550 μm into the adipose layer between days 7 and 15.One important finding is that chemical depilation does not affect the telogen thickness of skin‐the teleogen values for the epidermis and dermis immediately prior to and immediately after depilation were similar to those 23 days later at the beginning of the next telogen phase.
Formation of new rod photoreceptor synapses onto differentiated bipolar cells in goldfish retina
Authors: Kock Jan‐Henrik , Stell William K. 
Published: February 2005

AbstractIn goldfish new rods are continuously added to the entire retina at a rate that assures stable rod density, while the densities of other neurons decrease. The b1 bipolar, known to contact every rod within its dendritic domain, was used to determine the fate of these newly formed rods.Golgi‐stained b1 bipolars were sectioned serially at 0.5 μm in the plane of the receptor terminals and reconstructions of their rod and cone contacts were prepared from camera lucida drawings.The newly formed rods are accommodated within the dendritic trees of alreadyformed b1 bipolars at a rate of about one new rod synapse/bipolar/month. During growth from about 6 months to 5 years of age the number of synapses onto each b1 bipolar increases by 50%. Concomitantly the dendritic tree area increases by about 50%, and the density of rod‐b1 synapses remains constant at about one synapse/11 μm2. Assuming a dendritic coverage factor of 1, the b1 bipolars will contact every retinal rod. The numbers of cones contacted and not contacted do not significantly change. The overall dimensions of b1 bipolars increase with retinal growth and new branches are added to their dendritic trees.These observations show that new rods added to adult goldfish retina form synapses with old bipolars. Some functional inferences are also made.
Distribution of fibronectin on the migratory pathway of primordial germ cells in mice
Authors: Fujimoto Toyoaki , Yoshinaga Kazuya , Kono Ichiro 
Published: February 2005

AbstractThe distribution and localization of fibronectin (FN) on the migratory pathway of primordial germ cells (PGCs) in mouse embryos were studied immunocytochemically at the light and electron microscopic levels. In embryos 9.5 to 11.0 days of gestation, the dorsal mesentery as the final region through which PGCs migrate was rich in FN. At this stage, migrating PGCs often showed amoeboid features with pseudopods in contact with neighboring mesentery (mesenchymal) cells. With the electron microscope, the reaction product to FN was visualized on the surfaces of somatic cells and of PGC pseudopods and at the site of contact between PGCs and somatic cells. Abundant extracellular FN was also found, probably binding with the extracellular matrices. By 11.5 to 12.0 days, when PGCs had arrived in the gonadal anlage, FN reaction had weakened or disappeared in the dorsal mesentery. Thus, the results suggest that FN plays a significant role in the migration of PGCs at least in the last portion of the migratory pathway.
Morphometric evaluation of diabetes‐associated ovarian atrophy in the C57BL/KsJ mouse: Relationship to age and ovarian function
Authors: Garris David R. , Williams Sarah K. , West Lee 
Published: February 2005

AbstractProgressive, diabetes‐associated ovarian atrophy was analyzed in C57BL/KsJ diabetic (db/db) and control (+/?) mice between 2 and 16 weeks of age. Tissue changes were histologically and morphometrically analyzed and compared with ovarian functional indices (i.e., serum estradiol and progesterone) and metabolic (i.e., glucose uptake and estradiol sequestration) parameters. No significant differences were found between the ovarian follicular populations of either group at 2 and 4 weeks of age. However, between 4 and 8 weeks, the ovaries of diabetic mice exhibited marked stromal and follicular degeneration and an associated decline in the population of viable follicles as compared with controls. Between 8 and 16 weeks of age the follicular atrophy in the diabetics became more marked, as compared with controls, with the accumulation of intracellular lipid pools accenting the tissue degeneration and adiposity observed in both follicular and stromal compartments. In addition, ovarian function was depressed after 6 weeks of age in diabetic females as compared with controls as indicated by lowered serum estradiol and progesterone levels. Ovarian glucose uptake was enhanced in diabetic females while the ability of the ovary to sequester radiolabeled estradiol declined between 4 and 16 weeks of age as compared with controls. These data indicate that ovarian dysfunction in the (db/db) mutant mouse is associated with follicular atrophy, adiposity, impaired steroidogenesis, and imbalanced glucose utilization. These events occur in temporal association with the onset and progressive exacerbation of the hyperglycemic condition. It is suggested that ovarian involution in these mutants is directly related to an impaired follicular ability to metabolize properly the elevated intracellular glucose concentrations that develop in the (db/db) mice as compared with controls.
The vascular supply of the rat tympanic membrane
Authors: Albiin Nils , Hellström Sten , Salén Bengt , Stenfors Lars‐Eric , Wirell Staffan 
Published: February 2005

AbstractThe vascular supply of the rat tympanic membrane (TM) was studied by means of otomicroscopy, angiography, acrylic casts, and light microscopy. The branches of the external carotid artery in the external auditory meatus were found to vascularize (1) the pars flaccida, (2) the manubrial part of the pars tensa, and (3) the junction between the fibrocartilaginous ring of the TM and the tympanic sulcus of the temporal bone. The TM vessels of areas 1 and 2 were found beneath the squamous epithelium, close to mast cells and nerve bundles. Vessels originating from the tympanic cavity (also probably emanating from the external carotid artery) supplied the periphery of the pars tensa with minute branches, localized immediately beneath the tympanal epithelium. The portion of the pars tensa between the manubrial part and the periphery lacked a vascular system. Upon mechanical stimulation (gentle pressure on the handle of the malleus), the normally visible vessels dilated and minute branches appeared. This dilation may be caused, at least partly, by a release of vasoactive substances from mast cells and/or nerves in its vicinity. Even under mechanical stimulation, a large portion of the pars tensa seemed to be devoid of vessels. The nutrition of this part may be served by diffusion, with nutrients originating from the vessels in the tympanal rim and along the handle of the malleus. The architecture of the attachment of the fibrocartilaginous ring to the bony sulcus of the temporal bone is quite unique. Thus, the flow in the dense vascular network between these structures may be affected by an altered tension in the pars tensa.
Occurrence of cardiac muscle in the hepatic portal vein wall of the mouse and rat
Authors: Yokota Reiko , Yamauchi Akio 
Published: February 2005

AbstractCardiac myocytes have been shown to occur in the tunica media and adventitia at the region near the hepatic end of the portal vein of the mouse and rat, and have been studied by electron microscopy in the mouse portal vein. They measured 3–10 μm in breadth at their nuclear level, possessed centrally located nuclei, and were connected with each other by the intercalated disk. In these myocytes in the mouse portal vein, sarcoplasmic reticulum was represented by a rather simple and loose network of the anastomosing tubules. The membrane‐bound granules, which closely resemble the atrial specific granules, were found in many of the mouse portal vein myocytes. Transverse tubules, 40–200 nm in diameter, were sometimes detectable at the Z line level. The nexus occupied about 3–5% of the whole junctional area between cardiac myocytes in the tunica media, whereas in the tunica adventitia the corresponding value was about 17%. Blood capillaries with fenestrated endothelium supplied the cardiac myocytes in the adventitia of mouse portal vein. The closest relationship between the adrenergic axon and portal vein cardiac myocytes was observed to be ca. 0.3 μm apart. The significance of these findings is discussed in relation to pulsations of the portal vein.
Morphometric and autoradiographic analysis of frontonasal development in the chick embryo
Authors: Patterson Scott B. , Minkoff Robert 
Published: February 2005

AbstractDimensional changes in the nasal processes were measured in chick embryos from Hamburger and Hamilton (1951) stages 20 through 27.5. Transverse measurements in the frontonasal region of freshly fixed embryos were compared to frontal sections of the nasal region of comparably staged embryos. These observations were correlated with autoradiographic studies of cell movement employing an implant labeling technique.Morphometric analysis indicated that between stages 20 and 25 the separation of the nasal pit orifices increased concidentally with rapid forebrain enlargement. Since the separation of the nasal pit fundi increased more rapidly, the orientation of the nasal pits changed. Autoradiographic studies indicated that lateral movement of medial nasal process mesenchyme into the base of the nasal groove and medial area at the base of the lateral nasal process had occurred. After stage 25, the separation of the nasal orifices declined dramatically, coincidental with rapid orbital enlargement. In contrast, the separation of the nasal pit fundi was maintained. It is proposed that nasal development of the chick embryo may be governed initially by forebrain enlargement and associated lateral movements of mesenchyme in the medial nasal processes, resulting in reorientation of the invaginating nasal placodes; subsequently, orbital enlargement and an associated medial redirection of growth of the lateral nasal processes assumes greater significance to the continued development of the frontonasal region.
Scanning electron microscopy of the subarachnoid space in the dog: Inflammatory response after injection of defibrinated chicken erythrocytes
Authors: Persky Bruce , Low Frank N. 
Published: February 2005

AbstractThe leptomeningeal reaction and the cerebrospinal fluid reaction of the canine inflammatory response were investigated concurrently. One‐half milliliter cerebrospinal fluid (CSF) was withdrawn from the cisterna magna of 17 anesthetized mongrel dogs and analyzed. Using this same spinal tap, control and experimental animals were injected with 0.5 ml sterile saline and 0.5 ml defibrinated chicken erythrocytes, respectively. A second spinal tap was performed 2 to 168 hr later. The CSF from the first spinal tap contained less than 1 WBC/mm3. The cell population was unchanged in the second spinal tap of control animals. In experimental animals, the WBC population increased more than 100‐fold by 24 hr. Polymorphonuclear cells (PMNs) appeared in the CSF first, followed by lymphocytes and monocytes. Injected erythrocytes seemed trapped in the subarachnoid space (SAS), especially in the inner sheet of the arachnoid mater. The leptomeninges had a substantial increase in free cells without fibrosis. Pial and leptomeningeal cells of the arachnoid trabeculae appeared swollen. Two hours after injection, chicken erythrocytes were phagocytosed by pial cells, macrophages, and free cells adherent to the leptomeninges. The epiplexus cell populations for saline‐control and erythrocyte‐experimental animals were similar, suggesting that the choroid plexuses were not a gateway for PMN, lymphocyte, or monocyte infusion into the SAS.
An ultrastructural analysis of dog mastocytoma cells and normal mast cells
Authors: Calonico Lynne D. , Phillips Martin J. , McDonald Donald M. , Gold Warren M. 
Published: February 2005

AbstractA well‐differentiated dog mastocytoma was characterized ultrastructurally using morphometric, histochemical, and biochemical methods. The ultrastructure of cells in the intact tumor was compared to the morphology of cells disaggregated from the tumor and cultured for periods as long as 4 weeks and to normal dog connective tissue mast cells. Most of the tumor cells contained histamine (mean = 5.81 pg/cell), demonstrated chloroacetate esterase activity histochemically, stained metachromatically with toluidine blue, and were similar in ultrastructure to normal dog mast cells. The proportion of mast cells in this tumor averaged 67%; eosinophils, fibroblasts, plasma cells, and macrophages also were present. The mean diameter of mast cells (12.79 μm) and the mean diameter of their cytoplasmic granules (473 nm) were similar to those reported for mast cells and mastocytoma cells from various species. The heterogeneity in appearance of the mastocytoma granules is consistent with a variable degree of granule maturation. After disaggregation or periods of culture ranging from 2 days to 4 weeks, the mean granule diameters were 15% larger than those measured in the intact mastocytoma cells, though other morphological features remained unchanged. Although the cells retained their distinct morphological features for at least 4 weeks, some of their physiological responses were lost after 1 week in culture. Our study showed that dog mastocytomas can be a source of a large, relatively homogeneous population of cells that are useful for elucidating some of the structural and functional properties of mast cells.
Three‐dimensional structure of the murine muscle‐tendon junction
Authors: Trotter J. A. , Samora A. , Baca J. 
Published: February 2005

AbstractAt the muscle‐tendon junction of skeletal muscle fibers the structural interface between muscle cell and connective tissue is amplified by tapering, by indentation, and by surface folding. The precise form taken by the surface folds has been unknown due to a lack of studies on the three‐dimensional geometry of the muscle‐tendon junction. Analysis of this region by scanning electron microscopy, using conventional preparative techniques, is uninformative because the muscle surface is covered by connective tissue. Removal of the connective tissue from individual murine muscle fibers by incubation of fixed fibers in hot HCI, followed in some instances by treatment with collagenase, permits SEM analysis of the uncovered fiber ends. The muscle fiber end is characterized by surface specializations in the form of anastamotic cylindrical folds. Transmission electron micrographs of cross sections and of serial longitudinal sections of muscle fiber ends confirm that the SEM observations are correct.