bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shaping of the chick neuroepithelium during primary and secondary neurulation: Role of cell elongation
Authors: Schoenwolf Gary C. , Powers Monica L. 
Published: February 2005

AbstractCell elongation is a cardinal event in formation and shaping of the neuroepithelium during both primary and secondary neurulation. This study had three purposes. The first was to clarify the role of microtubules in maintaining the elongated configurations of chick neuroepithelial cells. Neuroepithelial cells of the neural plate (the rudiment of the primary neural tube) and medullary cord (the rudiment of the secondary neural tube) reduced their heights an average of approximately 25% when their microtubules were depolymerized, but most cells remained considerably elongated and columnar. Complete rounding up occurred only as cells entered metaphase where they arrested. These results suggest that microtubules as well as other factors are required to maintain the fully elongated configurations of cells composing epithelial sheets. The second purpose of this study was to evaluate the hypothesis that neuroepithelial cell elongation plays a major role in narrowing of the neural plate. To do this, the width of the neural plate was examined after microtubule depolymerization and repolymerization. As the heights of neuroepithelial cells decreased with loss of their microtubules, the width of the neuroepithelium increased roughly proportionately; subsequent repolymerization with concomitant cell elongation resulted again in neural plate narrowing. Thus, the hypothesis is supported. The third purpose of this study was to examine the roles of cell rearrangement and change in neuroepithelial cell or extracellular volume in neural plate narrowing and extension. Extensive cell rearrangement, resulting in net cell loss from the width of selected, representative levels of the neural plate, does not seem to play a major role in plate narrowing, but decreases in cell or extracellular volume are likely involved. Further studies are necessary to complete our understanding of the mechanisms driving neural plate shaping and bending.
Physiological role of skeletal muscle glycogen in starved mice
Authors: Sakaida Minoru , Watanabe Jun , Kanamura Shinsuke , Tokunaga Hirohiko , Ogawa Ryokei 
Published: February 2005

AbstractTo study the physiological role of skeletal muscle glycogen in starved animals, effects of starvation on glycogen and glycogen phosphorylase (EC 2.4.1.1.) activity were studied in muscle fibers (morphologic study) and in whole muscles (biochemical study) of the rectus femoris muscle of mouse. Glycogen content in the liver of the starved animals was also measured. PAS reaction, strong in muscle fibers of fed animals, became weak predominantly in type IIB fibers after 2 days and almost disappeared after 4 days of starvation. Glycogen particles, numerous in the sarcoplasm between myofibrils of muscle fibers, decreased markedly predominantly in type IIB fibers after 2 days and almost disappeared after 4 days. Phosphorylase a activity, undetected in fibers of fed mice, appeared weak in type IIB fibers and very weak in type IIA fibers after 2 days and became moderate in type IIB fibers and weak in type IIA fibers after 4 days. Muscle glycogen content did not differ by 16 hours from the values of corresponding fed animals. However, liver glycogen content had already decreased after 8 hours and markedly so after 12 hours. The results support our hypothesis—“skeletal muscle glycogen is used for maintaining the blood glucose level in starved mice” (Hirose et al.: Anat. Rec., 216:133–138, 1986)—and show that type IIB fibers play a main role in maintaining the glucose level and that muscle glycogen is utilized after depletion of liver glycogen.
Comparative development of gastrin and somatostatin cell populations in the pancreas, stomach, and duodenum of the rat during the perinatal period
Authors: Onolfo Jean Philippe , Lehy Thérése 
Published: February 2005

AbstractThe comparative growth patterns of endocrine gastrin and somatostatin cell populations were examined in the rat, during the perinatal period, to investigate possible relationships between their development and that of gastric acid secretion, gastrin and somatostatin hormones being implicated in the regulation of acid secretion. Total cell populations were estimated daily in the pancreas, stomach, and duodenum, by using a quantitative morphological method, from 19 days postcoitum to 8 days postpartum.In the pancreas, both cell types were present at 19 days postcoitum. After increasing, gastrin cells abruptly dropped from 4 days postpartum, while somatostatin cells continued to increase. In the stomach, gastrin cells seemed to appear at 19 days postcoitum, increasing with age. Somatostatin cells appeared only after birth and could be precisely quantified from 4 days postpartum. In the duodenum, the two cell types were present in similar numbers at 19 days postcoitum and increased similarly with age.Comparison of gastrin and somatostatin cell developmental behavior with previous data on the ontogeny of acid secretion shows a parallelism between the appearance of basal H+ fluxes at 20–21 days postcoitum and the high daily multiplication of the gastrin cell number in the three organs. Additionally, the marked decrease of pancreatic gastrin cell population at 4 days postpartum and the simultaneous development of the gastric somatostain cell population might explain, among other mechanisms, the diminution of gastric acid secretion noted after birth.
The effect of nerve section on the incidence and distribution of gap junctions in the odontoblast layer of the cat
Authors: Holland G. R. 
Published: February 2005

AbstractGap junctions are numerous in the odontoblast layer of the dental pulp and may link sensory axons to odontoblasts. If these junctions do link axons and odontoblsts, they, together with the axons, should disappear after cutting the pulpal nerves centrally. Under general anesthesia the inferior alveolar nerve on one side of two young adult cats was sectioned. Under general anesthesia the animals were perfused with fixative 56 hours later and the coronal dental pulp prepared for electron microscopy. Ultrathin sections were examined from the level of the pulpal cornu and levels approximately one, two, and three mm below this. The incidence of cell processes and gap junctions was measured at different distances from the pulp predentin junction, and operated and control sides compared.The odontoblast layer at the level of the cornu differed from elsewhere in having, on the control side, a greater density of cell processes and gap junctions and in having clearly recognizble axons approaching to within 5 to 10 μm of the predentin. The only statistically significant changes after nerve section occurred in this layer and consisted of a decline in the incidence of cell processes and of gap junctions that link one cell process to another. There was no significant difference between the operated and control sides in the number of gap junctions linking cell processes to recognizable cell bodies.The odontoblast layer in the pulpal cornu contained substantial numbers of unsheathed axons, many presumably en route to the dentin. These axons may participate in gap junctions that link them to other cell processes, possibly even other axons. No clear evidence was found of junctions involving axons and identifiable odontoblast cell bodies.
Effect of surgical sympathectomy on bone remodeling at rat incisor and molar root sockets
Authors: Sandhu H. S. , Herskovits M. S. , Singh I. J. 
Published: February 2005

AbstractSympathectomy was carried out in 4‐week‐old Sprague‐Dawley rats by unilateral surgical removal of the superior cervical ganglion. Sham‐treated rats served as controls. All rats were injected with tetracycline hydrochloride at surgery as well as 36 hr prior to sacrifice. Rats were killed at 7, 14, or 21 days following sympathectomy. Mandibular periosteal and endosteal surfaces were analyzed by fluorochrome morphometry. Osteoclasts were identified by acid phosphatase staining, and incisor and molar root sockets were analyzed morphometrically. Following sympathectomy, periosteal and endosteal apposition as well as the rate of mineralization were significantly lower. At the same time, a significant increase in the number of osteoclasts per socket as well as in active and inactive bone resorption surfaces was also seen. All parameters, however, returned to normal values 2–3 weeks after sympathectomy. The data provide the first direct quantitative evidence that sympathetic neurons modulate bone resorption and bone remodeling in vivo.
Expression of type I and III collagen during morphogenesis of fetal rat testis and ovary
Authors: Paranko Jorma 
Published: February 2005

AbstractThe distribution of interstitial collagen type I and III was studied immunocytochemically and ultrastructurally in the fetal rat testis and ovary from the undifferentiated stage (day 12) until birth. The results suggest that there is a correlation between the differentiation, organization, and abundance of the mesenchyme and the differentiation of the testicular vs. ovarian cords. Type III collagen was already present in the undifferentiated gonadal mesenchyme, and it appeared at an early stage around the organizing gonadal cords. Type I collagen appeared later in a similar mesenchymal distribution as type III collagen. Fragmentation of the subepithelial basement membrane in the gonads starting morphogenesis was considered to indicate that the surface epithelium participates in the gonadal cord formation. The expression of type III collagen at first on the surface of the developing testicular cords and later around the ovarian cords suggests that the mesenchymal premyoid cells are actively involved in the male cord formation. Focal discontinuities were found in the basement membrane of the ovarian cords, which in part were separated from each other by a ramified and relatively sparse mesenchyme. A complex linkage between the cytoskeleton and the extracellular matrix is illustrated both in the cord forming Sertoli and granulosa cells, and in the adjacent mesenchymal cells. Depletion of the mesenchyme and the basement membrane around the germ cell‐granulosa cell associations of the wide ovarian medullary cords may be causal for their subsequent degeneration.
The effects of vinblastine on the secretory ameloblasts: An ultrastructural, cytochemical, and immunocytochemical study in the rat incisor
Authors: Nanci A. , Uchida T. , Warshawsky H. 
Published: February 2005

AbstractSecretory ameloblasts synthesize the organic matrix of enamel and secrete it at two distinct “putative secretory sites” characterized by membrane infoldings (Nanci and Warshawsky, 1984a). The antimicrotubular agent vinblastine sulphate interferes with secretion. We have examined the effect of this drug on the ameloblast secretory sites and re‐evaluated the effect on the intracellular organization of the cell by using conditions that optimize fixation, cytochemistry (ZIO), and immunocytochemistry. Associated with the disappearance of secretory granules and Golgi‐related structures from Tomes' process was the loss of membrane infoldings at secretory sites. The Golgi apparatus appeared fragmented and numerous granule clusters were found throughout the cell body. These clusters were often seen in relation to extracellular patches of material in which no crystallites were seen. Immunocytochemistry revealed the presence of enamel proteins in the protein synthetic organelles, including various granule types, in lysosomes and in the extracellular patches. These data suggest that ameloblasts under the effect of vinblastine carry on secretory activities, but the product is not routed to the usual sites. It was confirmed that membrane infoldings characterize the sites where enamel proteins are normally secreted.
Leydig cell differentiation during maturation of the rat testis: A stereological study of cell number and ultrastructure
Authors: Zirkin B. R. , Ewing L. L. 
Published: February 2005

AbstractIn an effort to further understand the basis for the changes in steroidogenesis known to occur during sexual maturation in the rat, we examined by quantitative morphologic methods the number and ultrastructure of Leydig cells in fetal rats (days 18–20 of gestation) and in rats from days 2 to 3 of age through adult. Quantitative light microscopic analyses indicated that Leydig cell number, when expressed per unit volume of testis, was very high in fetal rat testes, fell significantly in testes of days 2 to 3 rats, and subsequently rose significantly. When Leydig cell number was expressed per testis rather than per unit volume of testis, the results indicated that testes of fetal rats and rats of days 2 to 3 contained the same number of Leydig cells; after the neonatal period, significant increases in Leydig cell number per testis occurred in concert with increases in testis weight. Quantitative electron microscopic studies revealed significant differences in the ultrastructure of fetal and adult populations of Leydig cells. For example, Leydig cells of fetal and neonatal rats contained abundant lipid, whereas Leydig cells, of weeks 7 to 8 and adult rats contained little. Stereological analyses also revealed dramatic changes in smooth endoplasmic reticulum and inner mitochondrial membrane surface areas during sexual maturation, both per cell and per testis. These findings are discussed with respect to the steroidogenic capacity of the testis during sexual maturation.
Localization of immunoreactive calcitonin gene‐related peptide in thyroid C cells from various mammalian species
Authors: Kameda Yoko 
Published: February 2005

AbstractLocalization of immunoreactive calcitonin gene‐related peptide (CGRP) in thyroid C cells from various mammalian species was investigated by the immunoperoxidase method. In many animal species including dogs, cats, cattle, monkeys, rats, and rabbits, almost all C cells revealed an intense immunoreactivity for CGRP; the cytoplasm of C cells was filled with reaction products for CGRP. In these animal species, calcitonin and CGRP coexisted in the C cells. However, in some species including pigs, mice, hamsters, and guinea pigs, the CGRP immunoreactivity of C cells was weak or negative. It was concluded that there was a considerable variation in CGRP immunoreactivity of C cells from species to species. In rabbits and guinea pigs, almost all C cells were also intensely immunoreactive to antisomatostatin antiserum, whereas in other animal species including dogs, cats, cattle, monkeys, rats, pigs, mice, and hamsters only a few C cells were immunoreactive to somatostatin. Three peptides–calcitonin, somatostatin, and CGRP—are synthesized alone in rabbit C cells. Thus, there was no relation between CGRP and somatostatin concerning the existence of both peptides in thyroid C cells.
Bursal secretory cells: An electron microscope study
Authors: Olah Imre , Glick Bruce 
Published: February 2005

AbstractIn addition to lymphocytes, macrophages, and epithelial cells, the bursa medulla possesses a cell we have named the secretory cell. The secretory cell, which makes up approximately 0.5% of the bursal cell population, exhibits an eccentric nucleus with a chromatin pattern similar to that of a small lymphocyte and an elongated cytoplasm with one or more cell processes. The electron‐dense cytoplasmic granules of the immature secretory cell are localized around the cytocentrum, while in the mature secretory cell these granules are situated beneath the cell membrane of one process. The granular location endows a polarized appearance to the secretory cell. The surface of the membrane is covered with a finely spotted flocculated substance, which may originate from a granular discharge. The round, ovoid, or irregular‐shaped granules reveal a homogeneous or distinctive internal pattern. The cortico‐medullary border may be the germinal layer of the bursal medulla. The bursal secretory cell is a modified dendritic cell with possible endocrine functions that may be important in B‐cell induction.
Attachment of neural crest cells to endogenous extracellular matrices
Authors: Brauer Philip R. , Markwald Roger R. 
Published: February 2005

AbstractNewly emerging neural crest (NC) cells will enter either the lateral pathway under the surface ectoderm or the vental pathway along the neural tube depending on the axial level (Pratt et al.: Dev. Biol., 44:298–305, 1975; Thiery et al.: Dev. Biol., 93:324–343, 1982; Newgreen et al.: Cell Tissue Res., 221:521–549, 1982; LeDouarin et al.: In: The Role of Extracellular Matrix in Development. Alan R. Liss, Inc., New York, pp. 373–398, 1984; Brauer et al.: Anat. Rec., 211:57–68, 1985). A number of studies have shown a correlation between the type of extracellular matrix (ECM) associated with adjacent tissues (e.g., ectoderm, neural tube, and mesoderm) and the initial pathway taken by NC cells. Our working hypothesis is that the direction of NC cell migration (ventral vs. lateral pathway) depends on the composition of the ECM associated with the surface ectoderm and its ability to support NC cell attachment. In this study, we tested this hypothesis by isolating endogenous ECM associated with the ectoderm of each region and examining the ability of each endogenous ECM to support cranial and trunk NC cell attachment in vitro. Results indicated that both cranial and trunk NC cells preferentially attached to cranial ectodermal ECM as compared to trunk ectodermal ECM. The differences in NC cell attachment were not due to a preferential adsorption of cranial ectodermal ECM onto the ECM‐conditioned plastic substrate over trunk ectodermal since approximately equal amounts of ECM bound to the plastic. These results supported the hypothesis and provide evidence that endogenous ectodermal ECM may be one factor potentially responsible for directing the NC cells along a ventral or a lateral pathway.
Effects of colchicine on the shape of chick neuroepithelial cells during neurulation
Authors: Fernandez J. G. , de Paz P. , Chamorro C. A. 
Published: February 2005

AbstractWe have analyzed the effects of colchicine on the cell shapes in chick neuroepithelium. Cell shapes were ascertained by the position of the nucleus in plastic serial sections. We tested three colchicine doses (5 × 10−5 M, 5 × 10−6 M, and 5 × 10−7 M) by two experimental treatments (in ovo and in vitro). Colchicine treatment in vitro is always effective in depolymerizing microtubules of neuroepithelial cells and reduces the percentages of wedge‐shaped cells in the median area of neuroepithelium. The same effect can be observed when the embryos are treated with 5 × 10−5 M or 5 × 10−6 M colchicine in ovo. A concentration of colchicine of 5 × 10−7 M in ovo cannot disrupt microtubules in stage 8 and stage 10 embryos, and the percentage of wedge‐shaped cells is the same as that of the untreated cells. In stage 6 embryos this colchicine dose effects the microtubules and the percentages of wedge‐shaped cells. These facts are interpreted in respect to variations in microtubular resistance to microtubular‐disrupting agents that are shown by the neuroepithelial cells from different developmental stages.
Loss of sensory neurons after sciatic nerve section in the rat
Authors: Schmalbruch Henning 
Published: February 2005

AbstractIn this study, the loss of sensory neurons in the rat was assessed after sciatic nerve section hat birth and at 4 weeks of age. The neuronal defict in ganglia L4–L6, 39–89 weeks after neonatal denervation, was 10,000–17,000. The nerve contains about 19,000 afferent axons, so some axotomized neurons survived. Degenerating perikarya were absent, probably because all surviving neurons had reestablished target contacts. Sectioning the nerve at age 4 weeks, in five rats, after 19–92 weeks had caused the death of 7,000–11,500 neurons. Whether the nerve regenerated or not in these rats apparently did not influence the extent of neuron death. Nevertheless, no deficit was observed in a sixth rat in which muscle reinnervation was very good. Therefore, the results are inconclusive with respect to the effect of axonal regeneration. Ganglia of rats operated at age 4 weeks regularly contained perikarya with axonal reaction; this supports the notion that some mature neurons are able to permanently survive without target contact. There was no evidence for selective loss of large or small neurons after nerve section at birth or at age 4 weeks.The extent of cell loss in individual ganglia varied, indicating varying contributions of the three ganglia to the nerve. Hence, it is not possible to quantify the effect of experimental conditions on the number of sensory neurons when only one of the several ganglia contributing to the nerve is investigated.
Maturation changes of the plasma membrane of rat spermatozoa observed by surface replica, rapid‐freeze and deep‐etch, and freeze‐fracture methods
Authors: Toyama Yoshiro , Nagano Toshio 
Published: February 2005

AbstractRat spermatozoa from the epididymis and ductus deferens were observed by surface replica, rapid‐freeze and deep‐etch, and conventional freeze‐fracture methods. By the surface replica method, parallel periodical ridges were observed in the acrosomal region of the spermatozoa from the distal part of the cauda epididymis (zone 6) and from the ductus deferens. The periodicity of the ridges forming a domain was about 35 nm. A quantitative analysis of the spermatozoa along the reproductive tract indicated that 39.4% and 73.5% of the population in zone 6 of the epididymis and in the ductus deferens, respectively, had the domain. None of the spermatozoa from zone 1 through zone 5 had the domain. The results of the rapid‐freeze and deep‐etch procedure showed that the ridges observed by the surface replica method consisted of linear arrangements of elliptical particles on the ES face of the plasma membrane. The particles were about 30 nm in length and 15 nm in width. On the corresponding PF face of the plasma membrane, linear arrangements of the intramembrane particles (IMPs) of about 8 nm in diameter were observed by both the deep‐etch and freeze‐fracture methods. The IMPs tended to run in paired parallel lines. A close relationship was observed between the lines of the elliptical particles on the ES and of the IMPs on the PF faces. The elliptical particle may be a protruded part of the IMP(s) or other protein(s) bound to the IMP(s).
Removal of collagen bundles in murine uterus during postpartum involution
Authors: Shimizu Kiyoshi , Hokano Masami 
Published: February 2005

AbstractThe localization of collagenolytic activity within the tissue compartments of the mouse uterus was investigated during postpartum involution. The rate of collagenase activity was measured by analysis of tissue levels of hydroxyproline from the day of parturition to the 10th postpartum day. Collagen bonding was analyzed by viewing birefringence induced by the picrosirius red‐binding technique. An attempt was made to interrelate quantitative analysis with the histologic distribution of collagen during postpartum days 1–10.Histologic and quantitative evidence indicated the following: (1) The collagenous compartments of the endometrium and myometrium differ in their response to the postpartum rise in collagenase activity; collagen degradation occurs primarily in the endometrium, that is, the myometrial collagen remains, but much of the endometrial collagen is removed. (2) Endometrial collagen is degraded particularly in the immediate subluminal compartment.