bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of lamellar bodies and subsurface cisterns in pyramidal cells and neuroblasts of hamster cerebral cortex
Authors: Buschmann Mb. Tank 
Published: February 2005

AbstractIn pyramidal cells of hamster frontal cortex lamellar bodies and subsurface cisterns sequentially occurred during development from newborn to three months of age. Neither of these two specializations of the rough endoplasmic reticulum was seen in neurons of the newborn. The first specialization that we observed was the subsurface cistern, which appeared at five days and showed a significant increase both in frequency and in length throughout development. The lamellar body was first seen at ten days of age. This specialization showed a peaking of frequency, length, and number of cisterns per body at 15 days, which subsequently decreased gradually to 3‐month‐old levels. The occurrence of lamellar body‐subsurface cistern complexes increased with age. We suggest that the lamellar body may be an ER specialization that is involved in an increased and/or stage‐specific protein synthesis in the young prior to the final maturation of the usual neuronal protein synthetic organelles, and that in the 3‐month‐old neurons, the lamellar body may be involved in modifying, storing or transporting metabolites received from the neuropil components via the subsurface cisterns. The subsurface cistern, on the other hand, by virtue of its location subjacent to the neuronal plasma membrane and of its increased frequency from birth to maturation, may be involved in the exchange of metabolites and nonsynaptic forms of communication at all ages.
The structure and distribution of the cross‐striated fibril and associated membranes in guinea pig photoreceptors
Authors: Spira Arthur W. , Milman Gordon E. 
Published: February 2005

AbstractExamination of longitudinally and transversely sectioned photoreceptor cells of the guinea pig retina revealed an aggregate of thin filaments forming a single cross‐striated fibril coursing through the full length of the non‐receptor portion of the cell. The fibril begins as the ciliary rootlet from the region of the basal body of the connecting cilium. From the basal body it passes between the mitochondria of the ellipsoid and along the Golgi zone of the myoid region of the inner segment, narrowing from an irregularly shaped bundle to a ribbon‐shaped aggregate. The fibril separates into discrete strands, each curving along the nucleus, reuniting into a single bundle to pass down the cell's axon, and terminating deep within the synaptic terminal. The fibril is flanked by two separate membranous saccules, each continuous along nearly its full length. The fibril's extensive course in the guinea pig and its association with continuous membranes necessitates a reexamination of earlier proposals for the function of cross‐striated filamentous structures in photoreceptor cells.
Occurrence and distribution of muscle spindles in masticatory and suprahyoid muscles of the rat
Authors: Maier Alfred 
Published: February 2005

AbstractThe occurrence and distribution of muscle spindles was studied in histochemically and conventionally stained serial cross sections of 6‐week‐old and adult rat masticatory and suprahyoid muscles. Spindles were present in moderate to large numbers in jaw closers, but they were absent in jaw openers and two of four muscles of an accessory suprahyoid group. In jaw closers, 67% or more of the total spindle population was concentrated relatively distant from the temporomandibular joint, in muscle portions which contained large numbers of extrafusal fibers reacting strongly for oxidative enzymes. Because of their location, spindles in these portions should be stretched more and, subsequently, should respond with a greater afferent discharge at any given muscle length than spindles situated nearer to the joint. Spindles in jaw closers, especially the medial pterygoid and deep masseter, often occurred in clusters and complex forms near the terminal branching of intramuscular nerve trunks. No such concentrations were seen in the two muscles of the accessory suprahyoid group that had spindles. The association in jaw closers of spindles with extrafusal fibers high in oxidative enzyme activity is consistent with the view that spindles are the sensory component of a reflex system that recruits these fibers for finely‐graded contractions in response to small internal length‐changes of the muscle (Botterman et al., 1978); however, in jaw openers and two muscles of the accessory suprahyoid group, the absence of spindles, coupled with the presence of large populations of extrafusal fibers high in oxidative enzyme activity, is not easily reconciled with this concept.
Alterations within the rat thyroid gland during vitamin A deficiency
Authors: Strum Judy M. 
Published: February 2005

AbstractThyroid glands from female rats kept vitamin A deficient for one, two, and three months were examined by electron microscopy. After one month on the diet, no consistent alterations were noted. After two months, the colloid in some follicles displayed a peripheral zone of decreased density. In addition, ultimobranchial follicles within the gland had become keratinized. After two to three months on the diet, cells were seen entering the colloid. Many of these cells were identified as follicular cells since they often occurred in groups and occasionally exhibited remnants of desmosomes. Often the cells within the colloid appeared vacuolated, and by light microscopy were thought to contain lipid. However, electron microscopy revealed that these cells contained many digestive vacuoles rather than lipid droplets.Quantitative and autoradiographic studies indicated that thyroids of vitamin A deficient rats took up less radioiodide than thyroids of control rats. The keratinization of ultimorbranchial follicles in vitamin‐A deficiency has been suggested as preliminary in the histogenesis of squamous cell carcinoma. However, an effect of vitamin A deficiency on thyroid follicular cells has not heretofore been reported. It's possible that the presence of follicular cells in the colloid reflects an accelerated turnover of these cells and could indicate an early pathological sign.
The surface structure of the completely and incompletely orthokeratinized oral epithelium in the rat: A light, scanning and transmission electron microscope study
Authors: McMillan M. D. 
Published: February 2005

AbstractMucosa from the hard and soft palates, molar gingiva, cheek and dorsal surface of the tongue of the rat was examined in the light microscope, following Mallory's triple connective tissue stain, and in the scanning and transmission electron microscopes. The epithelium covering the hard palate, gingiva, the smooth band of mucosa at the junction of the hard and soft palates, intermediate zones of the soft palate, fungiform papilla‐like structures in the central zone of the soft palate, the fungiform papillae, and the more superficial part and posterior surfaces of the filiform papillae of the tongue all exhibited complete orthokeratinization. The oral surfaces of the epithelial cells in all these areas had a honeycomb pattern of interconnecting ridges surrounding depressions. Imprints of the overlying cells that had been desquamated were apparent, and the lateral boundaries between the cells were formed by two raised ridges separated by a gap. The epithelium covering the cheek, central zone of the soft palate apart from the fungiform papilla‐like structures, lateral zones of the soft palate, gingival crevice, and the mucosa between the fungiform and filiform papillae of the tongue all exhibited incomplete orthokeratinization. The oral surfaces of the epithelial cells in all these areas were relatively smooth and did not exhibit a honeycomb pattern of interconnecting ridges. Imprints of the overlying cells that had been desquamated and the lateral boundaries between the cells were only very occasionally found. In the transmission electron microscope the outlines of the cells were compatible with the surface patterns seen in the scanning electron microscope. The possible relationships between the degree of orthokeratinization and ultrastructure of the various epithelia are discussed.
Cyclic changes in ciliation, secretion and cell height of the oviductal epithelium in women
Authors: Verhage Harold G. , Bareither Mary L. , Jaffe Randal C. , Akbar Maksood 
Published: February 2005

AbstractOviducts were obtained from women who elected to undergo sterilization either during a normal menstrual cycle, after the first trimester of pregnancy, or in the puerperium. The percent of ciliated cells, cell height and morphology of the fimbria and ampulla were determined and correlated with the stage of the reproductive cycle and plasma levels of the ovarian steroids. Mature ciliated and secretory cells were observed only at mid‐cycle. Atrophy, deciliation and loss of secretory activity coincided with elevated levels of serum progesterone. These degenerative processes continued during pregnancy. Ciliation, hypertrophy, and restoration of secretory activity occurred when serum progesterone was essentially undetectable and estradiol relatively low. During each menstrual cycle the secretory cells were observed to undergo a complete cycle of dedifferentiation‐differentiation, whereas 10‐12% of the ciliated cells lost and regenerated their cilia. Ciliogenic cells were frequently present in the epithelium obtained from women in the mid‐follicular phase. Fibrous granules, deuterosomes, procentrioles and ciliary buds were observed in the apex of these cells. Plasma levels of estradiol were higher during periods of atrophy and deciliation than they were during periods of hypertrophy and reciliation. It appears that the serum levels of estradiol were adequate to maintain a mature epithelium at all the reproductive stages included in this study. However, progesterone, when present, blocked the growth‐promoting effect of estradiol in the oviduct.
The structure of the sinus wall of the lymph node relative to its endocytic properties and transmural cell passage
Authors: Farr Andrew G. , Cho Yongock , de Bruyn Peter P. H. 
Published: February 2005

AbstractThe internal structure of cells lining the lymphatic sinus of the lymph node includes the presence of large bristle‐coated vesicles, transfer tubules, and vesicular organelles for the uptake and intracellular disposition of endocytosed material. The lining cells of the sinuses phagocytose particulate material from the lymph in the same manner as the sinusoidal endothelium of the bone marrow takes up particulates from the blood and, thus, are similar in this respect to the endothelial lining of the bone marrow sinusoids.Transmission and scanning electron microscopic examination of the lymphatic sinus wall in rat lymph nodes show that the walls of the lymphatic sinuses are continuous and do not have permanent apertures allowing free communication between the extrasinusoidal and intrasinusoidal compartments in the lymph node.Migrating lymphocytes cross the lymphatic sinus wall intracellularly, i.e., through the body of the lining cell, by making a temporary migration pore, which closes after the cell has reached the lumen of the sinus. In addition there are sporadic aggregations of macrophages in transmural positions. The direction of their movement is unknown.
Uptake of exogenous substances and marked infoldings of the fluorescent granular pericyte in cerebral fine vessels
Authors: Mato Masao , Ookawara Shigeo , Kurihara Kyoichi 
Published: February 2005

AbstractExogenous substances such as trypan blue and horseradish peroxidase administered intraventricularly are taken up by granular pericytes in cerebral fine vessels. These cells are provided with elongated and complicated infoldings. Pinocytotic vesicles occur often along the infoldings, and ends of infoldings are swollen and assume vesicular shapes. The specific morphology of the granular perithelial cells is considered to favor a removal of metabolic wates in cerebral tissue.
Characterization of intercellular junctions in the caudal portion of the developing neural tube of the chick embryo
Authors: Schoenwolf Gary C. , Kelley Robert O. 
Published: February 2005

AbstractThe types of intercellular junctions present within caudal levels of the chick neural tube (i.e., future lower thoracic and lumbosacral regions of the spinal cord) were determined by freeze‐fracture of stage 14 to 16 embryos. Two levels of the developing neural tube were examined: the region of the neurulation overlap zone–consisting of primary neural tube dorsally and secondary neural tube ventrally–and the portion of the primary neural tube located just cranial to the overlapping region. Gap junctions were the most numerous type of intercellular junction present within the primary neural tube. These junctions were located primarily in juxtaluminal areas, near the apices of neuroepithelial cells, and sometimes also at the bases of these same cells. In addition, focal, poorly defined tight junctions occasionally occupied juxtaluminal regions of the primary neural tube. The medullary cord (i.e., the immediate precursor of the secondary neural tube) and secondary neural tube contained gap junctions exclusively. Gap junctions were first found in these areas at the lateral borders of the medullary cord, concomitant with formation of this structure, and then at the interface between the elongated, peripheral cells of the cord and the irregularly shaped and loosely arranged central cells of this structure. Finally, gap junctions were distributed radially around secondary lumina formed by cavitation. The precise spatial and temporal correlation between the appearance of gap junctions and the specific changes occurring in cellular morphology and arrangement during secondary neurulation strongly suggest that gap junctions may have a role in coordinating cellular activities during formation of both the medullary cord and the secondary neural tube.
Revascularization of the freely grafted extensor digitorum longus muscle in the rat
Authors: Hansen‐Smith F. M. , Carlson B. M. , Irwin K. L. 
Published: February 2005

AbstractThe process of revascularization of free grafts of the extensor digitorum longus muscle in rats has been studied by gross, histological and electron microscopic methods. During the first day after transplantation the muscle is entirely avascular, and it consists of a thin peripheral zone of surviving muscle fibers and a large central area of ischemic muscle. The original blood vessels of the graft undergo a sequence of intrinsic and cell‐mediated destruction. Scattered sinusoidal vessels begin to grow into the graft starting on the second day, and ingrowing blood vessels progressively invade the deeper tissues of the graft. Most new vessels form in the connective tissues, but some vessels, especially larger ones, grow into persisting basal laminae from preexisting vessels and, occasionally, even into basal laminae from degenerated muscle fibers and nerves. The differentiation of new arterioles and venules in free muscle grafts is described. By the end of the first week, the entire graft is revascularized, and ultimately a fairly normal relationship between new capillaries and regenerating muscle fibers is established. In mature grafts, however, irregularities are sometimes found in the organization of smooth muscle cells associated with larger vessels.
The ultrastructure of monkey foveal photoreceptors, with special reference to the structure, shape, size, and spacing of the foveal cones
Authors: Borwein Bessie , Borwein David , Medeiros John , William McGowan J. 
Published: February 2005

AbstractA systematic electron microscopic study was made of the structure of foveal cones of Macaca spp. Transverse sections of inner (IS) and outer segments (OS) were made in sequence, from the pigment epithelial zone (PEZ) to the outer limiting membrane (OLM). The smallest diameters of hundreds of cone sections were measured from electron micrographs with a Zeiss particlesize analyzer, and analyzed statistically. Some details are also included about Cebus photoreceptors.It is claimed in the literature that foveal cones are rod‐like (cylindrical) and untapered. Our study shows the foveolar cone to be a tapered structure.There has been some confusion between the foveola, which is rod‐free, and the fovea, which has a high concentration of cones, but is not rod‐free. Within the fovea, as the ratio of cones to rods falls from ∞ to 1, with distance from the central bouquet of cones, the cone center‐to‐center distances increase, the inner segment diameters increase, and the number of cones/sq mm decreases.The tapered calycal processes are more massive in M. irus than M. mulatta, and the lateral fins are better developed. Lateral fins are not present in the foveola.The cones are arranged in straight lines.
The stem‐cell zone of the small intestinal epithelium. I. Evidence from paneth cells in the adult mouse
Authors: Bjerknes Matthew , Cheng Hazel 
Published: February 2005

AbstractStem cells in the small intestinal epithelium are known to differentiate into columnar, mucous, enteroendocrine, and Paneth cells. However, the site of initiation of stem‐cell differentiation has been unknown. To approach this problem we determined the site of stem‐cell differentiation along the Paneth cell line, using light microscopic morphometry and radioautography. The smallest Paneth cells containing the smallest granules were in positions 6 and 7, while the largest ones containing the largest granules were in positions 1 and 2 at the base of the crypt. Paneth cell death was less prevalent above position 3 than it was in position 1. Since cell size, granule size, and cell death are indicators of Paneth cell age, it was deduced that there is a gradient of Paneth cell age in the crypt base, with the oldest Paneth cells at the bottom, and the youngest at the top. After single injection or continuous infusion of 3H‐thymidine, the first labeled Paneth cells to appear were the highest Paneth cells in their crypt column. Later, labeled Paneth cells became more prevalent in lower positions, and, eventually, appeared in position 1. The size of granules in labeled Paneth cells increased with time. It was concluded that Paneth cells originate in position 5 or above and then migrate downward. These results are consistent with a stem‐cell zone hypothesis, which proposes that stem cells in positions 1–4 receive no inducement to differentiate. Only those stem cells that migrate up out of the stem‐cell zone into position 5 will be induced and then begin to differentiate.
The life history of cells in renewing systems
Authors: Leblond C. P. 
Published: February 2005

AbstractCell populations may be classified into three groups: static, which do not divide in the adult (e.g., neurons), expanding, which may divide but at a decreasing rate with age (e.g., kidney cells), and renewing, which undergo active division throughout life (e.g., blood cells, intestinal and seminiferous epithelium). The first two groups consist of nonrenewing populations whose cells usually survive as long as the body itself. In contrast, the cells of renewing populations have a short life, of the order of 2 to 3 days in the intestinal epithelium of rodents and 7 to 8 weeks in their seminiferous epithelium. In the present work, the life of a nonrenewing cell—the proximal convoluted tubule cell of kidney—is compared to that of the renewing cells of small intestine and testis.The proximal convoluted tubule cell arises during embryonic development, when it has few organelles, many free ribosomes, a pale nucleus with diffuse chromatin, and a large open‐network nucleolus. As the cell differentiates, organelles accumulate while free ribosomes decrease in number, chromatin masses appear in the nucleus, and the nucleolus becomes rather dense. With old age, some of the cells show features interpreted as senescence, particularly a small dense nucleolus.The short‐lived columnar cells of small intestine in adult rats arise from stem cells present in the base of the crypts. These cells have features similar to those of the embryonic proximal tubule cell, particularly many free ribosomes and a large open‐network nucleolus. The stem cells give rise to cells which ascend crypts and villi. Shortly after the cells reach the villus, they acquire a full set of organelles, suggesting maturity, while free ribosomes decrease in number and the nucleolus undergoes condensation. Meanwhile radioautographic tests indicate that the production by the cells of glycoproteins identified as intestinal enzymes reaches a high level. However, when cells arrive in the villus tip region, their activity decreases, as shown by reduced enzyme production, while the nucleolus appears atrophic. The cells are then lost to the lumen.The cells of the seminiferous epithelium also arise in the adult from stem cells with embryonic features. In the course of a complex differentiation, the nucleolus becomes atrophic and disappears. Soon thereafter the fragile spermatozoon stage is reached.Thus, the renewing cells of the adult show in rapid succession some of the features occurring slowly during the life of nonrenewing cells: origin from embryonic‐like elements, maturation, and senescence indicated by a fragile state before life's end.
Transport across endodermal cells of the chick yolk sac during early stages of development
Authors: Mobbs Ian G. , McMillan D. B. 
Published: February 2005

AbstractThe endoderm of the chick yolk sac mediates the transfer of materials from the yolk mass to the embryonic circulation. There is little evidence of endocytotic activity in the area pellucida, but the endodermal cells of the area vasculosa possess many microvilli and bristle‐coated pits and vesicles, as well as a canalicular system and vacuoles in the apical cytoplasm. Three tracers, horseradish peroxidase, ferritin, and latex spheres, were injected beneath the endoderm of both cultured embryos and embryos in ovo to study the pathway of uptake of extracellular materials. All tracers were sequestered in bristle‐coated pits (200–500 nm in diameter) of the endodermal cells of the area vasculosa, but not those of the area pellucida. Both horseradish peroxidase and latex spheres (and probably ferritin) were incorporated into pleomorphic intracellular yolk drops through bristle‐coated pits and vesicles, and then into apical vacuoles, which fuse with the intracellular yolk drops. Horseradish peroxidase and ferritin were also found within apical canaliculi. The apical junctions between endodermal cells prevented the intercellular passage of the tracers. A ‘topping‐up’ hypothesis is proposed whereby endodermal cells of the area vasculosa continually sequester extracellular yolk material, which is incorporated into a digesting intracellular yolk drop while, at the same time, digested yolk products are being transported across the vascular pole of the endoderm to the extraembryonic circulation and thence to the embryo.