bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unmyelinated fibers in the cervical and lumbar ventral roots of the cat
Authors: Wee Beth E. F. , Emery Dennis G. , Blanchard Janet L. 
Published: February 2005

AbstractVentral spinal roots at all spinal levels in humans contain many unmyelinated axons, as do all spinal roots of the cat which have been examined. Rats, however, have fewer unmyelinated fibers in cervical and certain lumbar ventral roots. To determine if unmyelinated fibers are distributed uniformly in ventral roots of the cat, cervical and lumbar ventral roots were examined by light and electron microscopy, and axons were counted. Lesions were made to determine the origin of unmyelinated fibers in ventral root L6. From 5 to 15% of the axons in cervical ventral roots are unmyelinated. This distribution of unmyelinated fibers in the cat is similar to the distribution in humans, although the cervical ventral roots of the cat contain relatively fewer unmyelinated fibers than the cervical ventral roots of humans. Approximately 24% of the axons in ventral root L6 are unmyelinated. More than 90% of these axons degenerate proximal to, but not distal to, a ventral rhizotomy and ipsilateral to a dorsal root ganglionectomy. Thus, most unmyelinated axons in ventral root L6 appear to arise from dorsal root ganglion cells. Much variation in the number and percent of unmyelinated axons in ventral roots at the same spinal level exists between individual cats and between opposite sides of the same cat.
The plasma membrane and matrix vesicles of mouse growth plate chondrocytes during differentiation as revealed in freeze‐fracture replicas
Authors: Akisaka Toshitaka , Gay Carol V. 
Published: February 2005

AbstractThe epiphyseal cartilage in mouse tibia and fibula was investigated with the freeze‐fracture method. Cytodifferentiation of growth plate chondrocytes was found to be marked by changes in both cell membrane and extracellular matrix vesicle membranes. Exocytosis and endocytosis were observed in all zones of differentiation, with endocytosis being predominant in the reserve and proliferative zones and exocytosis occurring with greatest frequency during hypertrophy. Intramembraneous particles (IMPs) on the plasma membrane were distributed evenly on the reserve and proliferative cell membranes, whereas in the hypertrophic zone IMPs tended to be distributed asymmetrically. Several types of matrix vesicles were identifiable on the basis of IMP distribution: IMP‐free, IMP‐aggregated, and IMP‐random. The distribution pattern of IMPs on vesicles varied with differentiation of the chondrocytes. For proliferative and prehypertrophic cells, most matrix vesicles belonged to the IMP‐random category. IMP‐aggregated and IMP‐free matrix vesicles became increasingly frequent in the later stages of differentiation, particularly in the late hypertrophic stage. IMPs were observed more frequently on the convex protoplasmic fracture face of matrix vesicles than on the concave exoplasmic fracture face, as was also observed for the plasma membrane. Matrix vesicles formation appears to occur by budding from chondrocyte projections and bulges at the smooth surfaces of the cells and from cell disintegration. Crystals of mineral were apparent in cross‐fractured matrix vesicles of the calcifying zone, but not in the other zones.
Studies of otoconia in the developing chick by polarized light microscopy
Authors: Ballarino Joanne , Howland Howard C. , Skinner H. Catherine W. , Brothers Edward B. , Bassett William 
Published: February 2005

AbstractUsing polarized light microscopy we were able to observe the mineralization patterns of embryonic and neonatal chick otoconia. We compared preparations of freshly dissected material spread under mineral oil to material that had been treated with various fixatives and dehydration agents. We found that the standard fixation agent, glutaraldehyde, and some immersion oils etche embryonic chick otoconia but that fixation with 70% acetone or 70% alcohol followed by dehydration to 100% acetone or 100% alcohol left the otoconia intact. The size and shape of freshly dissected chick otoconia observed with polarized light microscopy were similar to those of acetone‐fixed, critical‐point‐dried material examined by SEM. Embryonic forms of otoconia were found to have a fluted pattern that was different in morphology from otoconia found in hatched chicks and adults. Embryonic chick otoconia did not exhibit the multifaceted surface morphology seen in embryonic rat otoconia. Comparisons of the same fields of otoconia under phase contrast microscopy and polarized light microscopy indicated that the freshly dissected otoconia of embryos exhibit little or no unmineralized (nonbirefringent) material but that glutaraldehyde‐fixed otoconia exhibited unmineralized areas where etching had occurred. Size frequency distributions of freshly dissected embryonic and mature otoconia in five ages of embryos and hatched chicks were consistent with a hypothesized developmental sequence of otoconia.
Reconstruction of a type‐B configuration monkey sertoli cell: Size, shape, and configurational and specialized cell‐to‐cell relationships
Authors: Russell Lonnie D. , Gardner Richard J. , Weber James E. 
Published: February 2005

AbstractA model of a stage‐V monkey Sertoli cell was reconstructed from electron micrographs taken of semiserial sections. The configuration (type‐B) was one in which spermatids were positioned near the lumen, their heads occupying shallow cylindrical recesses at the apical portion of the Sertoli cell. The cell volume was calculated to be 4,100 μm3, the surface area 2,400.68 μm2, and the surface‐to‐volume ratio 0.58:1. The reconstructed cell extended from the basal lamina to the tubular lumen and was generally of the tall columnar type although its surface contour was highly irregular. The dimensions of the cell [centripetal (68.46 μm), circumferential (18.40 μm), and longitudinal (21.63 μm)] were determined and cell surfaces designated. Relative and absolute surface areas of the reconstructed cell which faced other Sertoli cells, germ cells, basal lamina, and tubular lumen were calculated. Junctions and surface specializations were enumerated, catalogued, and depicted on diagrams of the cell surface. Where appropriate, type‐A rat and type‐B monkey Sertoli cells were compared and discussed. Morphometry was utilized to analyze the relative surface areas of germ cells adjoining the reconstructed cell to determine the percentage of their surface facing cellular and acellular elements, and these data were compared to data obtained for the rat.
Cyclic formation and decay of the blood‐testis barrier in the mink (Mustela vison), a seasonal breeder
Authors: Pelletier R.‐Marc 
Published: February 2005

AbstractThe correlations between the germ cell population and the blood‐testis barrier were studied during puberty and throughout the reproductive cycle in a seasonal breeder, the mink. A classification of 12 stages, corresponding to the cellular associations appearing during the cycle of the seminiferous epithelium, was proposed and used to identify the stages of the cycle in pubertal mink. In adult mink, the reproductive cycle was divided into two spermatogenic phases–an active phase lasting 9 months, and an inactive phase lasting 3 months. The active spermatogenic phase was broken down into three distinct periods: the first spermatogenic wave, the peak of spermatogenic activity, and the last spermatogenic wave. Degenerating germ cells were found in comparable and relatively low proportions during puberty and during the first and last spermatogenic waves of the adult reproductive cycle. The permeability of the blood‐testis barrier to intravascularly infused electron‐opaque tracers (i.e., horseradish peroxidase and lanthanum) was tested at the time of the first spermatogenic wave at puberty and throughout the reproductive cycle of the adult. The relationship between epithelial permeability and germ cell populations prevailing during puberty and during the first and last spermatogenic waves of the adult active phase was the same. During puberty, the establishment of the blood‐testis barrier did not coincide with the appearance of a particular step of meiosis but was correlated with the development of a tubular lumen. In adult mink, the barrier cyclically decayed during the last wave of the active spermatogenic phase and reformed during the first wave of the next active phase. The decay and the reformation of the barrier were not coincident with the appearance or disappearance of a particular generation of the germ cell population from the seminiferous epithelium but were correlated with cyclic cytological changes in Sertoli cells and the rhythmic development and occlusion of the lumen. During the peak months of the active spermatogenic phase, however, a blood‐testis barrier secluded spermatogonia and young spermatocytes from older generations of germ cells. It is concluded that (1) during puberty and also during the first and last spermatogenic wave of the adult mink reproductive cycle, the development of germ cells is possible in the absence of a competent, impermeable blood‐testis barrier, and (2) the transient presence of a permeable epithelial barrier does not initiate an autoimmune response of sufficient magnitude to cause destruction of the seminiferous epithelium.
Gill microcirculation of the air‐breathing climbing perch, Anabas testudineus (Bloch): Relationships with the accessory respiratory organs and systemic circulation
Authors: Olson K. R. , Munshi J. S. D. , Ghosh T. K. , Ojha J. 
Published: February 2005

AbstractThe general macrocirculation and branchial microcirculation of the air‐breathing climbing perch, Anabas testudineus, was examined by light and scanning electron microscopy of vascular corrosion replicas. The ventral aorta arises from the heart as a short vessel that immediately bifurcates into a dorsal and a ventral branch. The ventral branch distributes blood to gill arches 1 and 2, the dorsal branch to arches 3 and 4. The vascular organization of arches 1 and 2 is similar to that described for aquatic breathing teleosts. The respiratory lamellae are well developed but lack a continuous inner marginal channel. The filaments contain an extensive nutritive and interlamellar network; the latter traverses the filament between, but in register with, the inner lamellar margins. Numerous small, tortuous vessels arise from the efferent filamental and branchial arteries and anastomose with each other to form the nutrient supply for the filament, adductor muscles, and arch supportive tissues. The efferent branchial arteries of arches 1 and 2 supply the accessory air‐breathing organs. Arches 3 and 4 are modified to serve primarily as large‐bore shunts between the dorsal branch of the ventral aorta and the dorsal aorta. In many filaments from arches 3 and 4, the respiratory lamellae are condensed and have only 1–3 large channels. In some instances in arch 4, shunt vessels arise from the afferent branchial artery and connect directly with the efferent filamental artery. The filamental nutrient and interlamellar systems are poorly developed or absent. The respiratory and systemic pathways in Anabas are arranged in parallel. Blood flows from the ventral branch of the ventral aorta, through gill arches 1 and 2, into the accessory respiratory organs, and then returns to the heart. Blood, after entering the dorsal branch of the ventral aorta, passes through gill arches 3 and 4 and proceeds to the systemic circulation. This arrangement optimizes oxygen delivery to the tissues and minimizes intravascular pressure in the branchial and air‐breathing organs. The efficiency of this system is limited by the mixing of respiratory and systemic venous blood at the heart.
Morphology and vascular anatomy of the accessory respiratory organs of the air‐breathing climbing perch, Anabas testudineus (Bloch)
Authors: Munshi J. S. D. , Olson K. R. , Ojha J. , Ghosh T. K. 
Published: February 2005

AbstractThe vascular organization and endothelial cell specialization of the air‐breathing organs of Anabas testudineus were examined by light and scanning electron microscopy of fixed tissue and vascular corrosion replicas. The vessels supplying blood to the lining of paired suprabranchial chambers and the plicated labyrinthine organs within the chambers are tripartite, having a median artery and paired, lateral veins. Hundreds of respiratory islets, the functional units of gas exchange, cover the surfaces of both the chamber and labyrinthine organ. A median islet artery supplies the central aspect of each islet and gives rise to numerous short arterioles from which the transverse channels are formed. Transverse channels are parallel capillary‐sized vessels that extend in two rows away from the medial arterioles and drain laterally into one of two lateral islet veins. Basally situated single rows of endothelial cells lining the transverse channels form thick, evaginated, tongue‐like cytoplasmic processes that project freely into the lumen from the tissue side of the channel. Other thin, septate, cytoplasmic exensions of the same cells form valve‐like septa that extend across the channel. Both the septa and tongue‐like processes appear to direct the red blood cells to the epithelial side of the channel and thus decrease the diffusion distance between the air and red cell. A large sinusoidal space lies under the transverse channels and may support the channels and even elevate them during increased oxygen demand. The epithelium covering the transverse channels is smooth, which enhances air convecton and minimizes unstirred layer effects. The epithelium between the channels contains microvilli that may serve to trap bacteria or particulates and to humidify the air chambers.
Light and electron microscope observations of the lymphatic drainage units of the peritoneal cavity of rodents
Authors: Tsilibary Effy C. , Wissig Steven L. 
Published: February 2005

AbstractFluid, particles, and cells are taken up from the peritoneal cavity by lymphatic drainage units, which, in the mouse and rat, are located along the peritoneal surface of the muscular portion of the diaphragm. The drainage units are composed of three specifically differentiated components: a lymphatic lacuna, a covering of lacunar mesothelium, and intervening submesothelial connective tissue. The units are drained by connecting lymphatic vessels that cross the diaphragm to empty into collecting lymphatic vessels running along the pleural surface of the diaphragm. The collecting lymphatics empty into parasternal lymphatic trunks. In this report, we briefly review critical features of the drainage apparatus and describe new observations, summarized below, about their structure.Around the rim of stomata, the mesothelial openings that lead into the lymphatic lacunae, plasma membranes of lacunar mesothelial cells and of lacunar enidothelial cells abut but are not linked to one another by recognizable junctional specializations. Lacunarendothelial cells often extend valve‐like processes that bridge the distal end of the channel beneath the stoma. The configuration of the endothelial processes may be complex. Occasionally, processes from fibroblasts in the submesothelial connective tissue adjacent to stomata make contact with the interstitial surface of lacunar endothelial cells. A discontinuous elastic layer in the submesothelial connective tissue spans the roof of each lacuna. Connecting and collecting lymphatics, which drain lymphatic lacunae, possess endothelial valves. Possible functions for each of these newly described structural features are discussed.
Neurogenesis in the vomeronasal epithelium of adult garter snakes: 3. Use of H3‐thymidine autoradiography to trace the genesis and migration of bipolar neurons
Authors: Wang Ruu Tong , Halpern Mimi 
Published: February 2005

AbstractUse of H3‐thymidine autoradiography and unilateral vomeronasal (VN) axotomy has permitted us to demonstrate directly the existence of VN stem cells in the adult garter snake and to trace continuous bipolar neuron development and migration in the normal VN and deafferentated VN epithelium in the same animal.The vomeronasal epithelium and olfactory epithelium of adult garter snakes are both capable of incorporating H3‐thymidine. In the sensory epithelium of the vomeronasal organ, H3‐thymidine‐labeled cells were initially restricted to the base of the undifferentiated cell layer in animals surviving 1 day following H3‐thymidine injection. With increasing survival time, labeled cells progressively migrated vertically within the receptor cell column toward the apex of the bipolar neuron layer. In both the normal and denervated VN epithelium, labeled cells were observed through the 56 days of postoperative survival. In the normal epithelium, labeled cells were always located within the matrix of the intact receptor cell columns. However, labeled cells of the denervated epithelium were always located at the apical front of the newly formed cell mass following depletion of the original neuronal cell population. In addition, at postoperative days 28 and 56, labeled cells of the denervated VN epithelium achieved neuronal differentiation and maturation by migrating much farther away from the base of the receptor cell column than the labeled cells on the normal, unoperated contralateral side tralateral side.This study directly demonstrates that basal cells initially incorporating H3‐thymidine are indeed stem cells of the VN epithelium in adult garter snakes. These stem cells differentiate and develop into neurons in the normal VN epithelium for normal neuronal turnover. Stem cells, which incorporated H3‐thymidine prior to unilateral VN axotomy, after axotomy differentiate and develop into neurons in the regenerating VN epithelium for replacement of the axotomized neurons. The life span of the labeled VN neurons may exceed 56 days. Postnatal neurogenesis during regenerative repair of the VN organ, however, is accompanied by rapid undifferentiated cell proliferation following axotomy, rapid cell migration, and a tendency for rapid cell turnover.
Ontogeny of langerhans cells in human embryonic and fetal skin: Cell densities and phenotypic expression relative to epidermal growth
Authors: Foster Carolyn A. , Holbrook Karen A. 
Published: February 2005

AbstractLangerhans cells (LCs) positive for HLA‐DR antigens were present in developing human epidermis by at least 7 weeks estimated gestational age (EGA). Most were negative for CD1 (T6) until 12‐13 weeks EGA when they underwent a dramatic increase in CD1 reactivity. To gain insight into the density of LCs during ontogeny and to assess whether their distribution was coordinated with epidermal growth, the number of cells positive for both HLA‐DR and CD1 antigens was determined relative to surface area and to volume of developing, interfollicular epidermis. LCs differed in their phenotype, distribution (follicular vs. interfollicular), size, and shape between 7 and 21 weeks EGA; however, during this period they maintained a statistically equivalent (P > .25) density (65 cells/mm2 and 1,750/mm3) even though the epidermis increased in thickness and the fetus rapidly expanded its surface area. While LCs were evenly distributed within the epidermal sheets at all gestational ages, those in embryonic skin were much smaller and less dendritic than the older cells. The density, size, and shape of LCs in developing skin seemed to be independent of epidermal status (e.g., thickness, stage of keratinization, and number of cell layers) but rather were correlated with gestational age. The number of fetal LCs, through at least 23 weeks EGA, was only 10‐20% of the adult LC density. Thus, we can conclude that the increase in LC density to adult levels must occur either during the third trimester or after birth.
Light microscopic study of the hypophyseal angioarchitecture in the rabbit
Authors: Foster W. G. , Boyd W. H. 
Published: February 2005

AbstractThis study describes the hy‐pophyseal angioarchitecture found in 79 adult New Zealand white rabbits. The pituitary glands and attached hypothalami were removed and carefully processed following routine histological methods, and the vascular organization was studied by light microscopy. Whole mounts of the pituitary median eminence complex were prepared and studied with a binocular dissecting microscope employing transmitted and epi‐illumina‐tion.Arterial blood was found to be directed primarily to the neurohypophysis by the superior hy‐pophyseal artery (SHA) and the inferior hypophy‐seal artery (IHA). A direct arterial blood supply was found to the adenohypophysis, but was limited solely to the pars intermedia by branches of the anterior hypophyseal artery (AHA) and the IHA. Capillaries of the pars intermedia were subdivided into an intermediate and a superficial plexus. The superficial plexus was situated between the intermediate plexus and the capillaries of the infundibular process. Capillaries of the superficial plexus did not form anastomoses between themselves, but ramified into the intermediate plexus to form a dense network of anastomosing capillaries that were continuous with capillaries of the pars distalis. A direct arterial blood supply was found only to the superficial plexus.
Expression of novel basement membrane components in the developing human kidney and eye
Authors: Kleppel M. M. , Michael A. F. 
Published: February 2005

AbstractThe distribution of two novel human, basement‐membrane (BM) collagens has been characterized by immunohistochemical analysis of developing and mature tissue using monoclonal antibodies specific for the non‐collagenous (NC1) domain of each molecule. A distribution more restricted than that of type IV collagen was observed. In the kidney, the 28K parent molecules appear relatively late, at the early capillary‐loop stage of glomerular development, whereas type IV collagen is present in all BM, including those of the ureteric bud, S‐form, primitive glomerulus, and vessels. Antibody to the Alport familial nephritis antigen (a 26K peptide), which is missing from epidermal BM and glomerular BM in Alport syndrome, reacted with the ureteral bud BM and all stages of glomerular BM development from the early capillary‐loop stage onward, but not with BM of more primitive glomeruli (vesicles and S forms).In the human fetal eye, the collagen molecules from which the 28K NC1 peptides are derived appear later in development than type IV collagen. They are present in trace amounts in Bruch's membrane but are not detected until after birth in the retinal internal limiting membrane and cuticular and non‐pigmented epithelial BM of the ciliary process. In contrast, the BM of the lens capsule and Descemet's membrane were reactive with anti‐28K antibodies early in development. In all instances, the 28K peptides are detected in BM that also contain the Alport antigen, although the latter is present in some BM not containing the 28K peptides. The distribution of Alport antigen and type IV collagen in developing eye is similar to that observed in the mature eye. The 28K parent molecules appear to be expressed in concert with the maturation of the BM, coincident with fusion of glomerular endothelial and epithelial BM, whereas the lens capsule BM and Descemet's membrane contain these restricted components much earlier in gestation.