bluuebunny/crossref_metadata_2025_split huggingface dataset:
The association of amorphous mineral deposits with the plasma membrane of pre‐ and young odontoblasts and their relationship to the origin of dentinal matrix vesicles in rat incisor teeth
Authors: Almuddaris M. F. , Dougherty W. J. 
Published: February 2005

AbstractYoung and preodontoblasts and matrix vesicles which occur in the presecretory region of incisor teeth of growing rats were examined in stained and unstained ultrathin sections in order to characterize sites involved in the initial mineralization of dentin. Common to pre‐ and young odontoblasts in the presecretory region were hemispherical membrane‐associated amorphous densities, measuring 5‐35 nm in diameter after fixation in glutaraldehyde‐osmium tetroxide or glutaraldehyde only. Amorphous densities were associated also with the limiting membranes of some vesicles in the extracellular matrix. Other vesicles in the extracellular matrix contained needle‐like crystalline deposits typical of dentinal matrix vesicles. Fully differentiated odontoblasts in more incisal regions of the tooth lacked plasma membrane‐associated amorphous densities. Neither amorphous nor crystalline densities were associated with any other cellular or subcellular structures in cells of the presecretory region. Flotation of ultrathin sections on solutions of EDTA or EGTA removed the amorphous densities from the plasma membranes, suggesting that the amorphous densities are calcium‐containing mineral deposits.Amorphous deposits were associated with the membrane of vesicular structures protruding from the surfaces of pre‐ and young odontoblasts, suggesting that vesicles found in the extracellular matrix arise by budding from the plasma membranes of pre‐ and young odontoblasts. The occurrence of amorphous mineral deposits in association with the limiting membrane of some vesicles in the extracellular matrix, and the occurrence of needle‐like mineral crystals within other matrix vesicles, suggest that an amorphous‐to‐crystalline phase transformation of mineral takes place within the matrix vesicle. The results of this study suggest that calcium‐binding sites associated with plasma membranes of pre‐ and young odontoblasts act as nucleating centers for primary mineral deposition in tooth dentin.
Peritoneal cells in mice: Quantitative and qualitative cell morphology
Authors: Abe Kazuhiro , Honma Sato , Ito Takashi 
Published: February 2005

AbstractPeritoneal free cells from 86 adult mice of both sexes were studied quantitatively and qualitatively.Peritoneal free cells were examined by use of a Coulter counter and channelyzer. The size‐distribution curves of peritoneal free cells thus obtained show three peaks, which were almost constant in position in all the cases examined. Thus, peritoneal free cells can be classified into three major populations according to cell size. The total cell numbers of the three populations, composed of small, medium‐sized and large cells are, on the average, 1.60 × 106, 2.47 × 106 and 2.90 × 106 in males and 2.05 × 106, 5.57 × 106 and 3.86 × 106 in females at 65 days of age. The number of medium‐sized cells is significantly greater in females than in males.Morphologically, three types of peritoneal cells, which constitute the three populations, can be distinguished cytologically and cytochemically, when examined by light microscopy and scanning and transmission electron microscopy. These type I, II, and III cells correspond closely to the three components in the size distribution curves in cell size.Type I cells are small lymphocytes. Type II cells are medium‐sized, round mononuclear cells which are distinguishable from lymphocytes by their ultrastructural characteristics, and they constitute a major population which can be separated from the other two populations. Type III cells are macrophages. In the peripheral cytoplasm, they have a labyrinth of tubules which open on the cell surface.
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Effects of colchicine on the morphology and prolactin secretion of rat anterior pituitary cells in monolayer culture
Authors: Antakly Tony , Pelletier Georges , Zeytinoglu Fusun , Labrie Fernand 
Published: February 2005

AbstractThe effects of incubation of rat anterior pituitary cells in monolayer culture with 10−6 M colchicine have been investigated during timeintervals extending from 1 to 96 hours. Prolactin release, as measured by radioimmunoassay, was rapidly inhibited by colchicine, this inhibition being accompanied by increased cellular prolactin content for up to 24 hours of treatment and followed by decreased values of cellular prolactin concentration at later time‐intervals. Immunocytochemical localization showed an increased positive reaction for prolactin up to 24 hours after colchicine treatment, whereas transmission electron microscopy demonstrated, in parallel, an increased number of intracellular prolactin secretory granules during the same interval. Longer periods of treatment (24–96 hours) resulted in the appearance of more lysosomes, autophagic vacuoles and microfilaments in the cells, whereas the number of Golgi elements was decreased. Following four hours of colchicine treatment and at later stages, microtubules could no longer be observed in the sections. Scanning electron microscopic data showed that colchicine treatment induced dramatic changes in the cell surface morphology: at short time intervals (4 and 8 hours), the number of microvilli decreased and the cell surface became folded, whereas, later, “bleb”‐like protrusions of variable dimensions partially covered the cell surface and seemed to be released from it. These data show a good correlation between secretory activity of prolactin‐producing cells and morphological changes induced by colchicine treatment.
Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. I. Morphometric methodology and hormonal correlations with cellular and nuclear volumes
Authors: Poole Max C. , Mahesh Virendra B. , Costoff Allen 
Published: February 2005

AbstractSerum prolactin (PRL) levels display regular patterns throughout the 4‐day rat estrous cycle. A morphometric analysis of mammotropes (PRL‐secreting cells) in the anterior pituitary was performed in an effort to quantify some of the ultrastructural events occurring prior to and during the secretion of PRL throughout the estrous cycle. In this study, a systematic sampling protocol applicable to the rat adenohypophysis was developed, which took into account the lack of synchrony in estrous cycles among the animals, the heterogeneity of the gland, and the number of cells required to yield a representative sample. These techniques were used to determine the cell, nuclear, nucleolar, and cytosol volumes, which were correlated with the changing levels of serum estradiol and PRL and pituitary PRL.Estradiol concentrations rose during late diestrus‐1 and continued rising in a pulsatile manner, reaching maximal levels during proestrus. The elevations of estrogen were accompanied by increases in nucleolar and nuclear volumes. However, at early estrus and on the afternoon of diestrus‐2, times at which it has been reported that progesterone levels are elevated, there was a dampening effect and these volumes declined. During early diestrus‐2, when estradiol levels began to rise, there were increases in nucleolar, nuclear, cellular and cytosol volumes, as well as increases in pituitary PRL; but at late diestrus‐2 there was a marked increase in nuclear and nucleolar volumes which was not accompanied by increases in cellular and cytosol volumes. During proestrus, two peaks of serum PRL were found, at 6 pm and 12 m, which were concomitant with increased nucleolar, nuclear and cellular volumes. The 6‐pm proestrous peak of PRL was preceded by elevated pituitary PRL; however, the 12‐m proestrous peak occurred when the pituitary PRL was minimal, even though nuclear and cellular volumes were elevated. This suggests that the 6‐pm release of PRL was derived from previously synthesized and stored hormone, while the 12‐m peak was the result of the immediate release of PRL, with little storage.
Ultrastructure of secondary neurulation in the chick embryo
Authors: Schoenwolf Gary C. , Delongo Judi 
Published: February 2005

AbstractFormation of the future lumbosacral level of the spinal cord was studied in two‐day‐old chick embryos by light and electron (transmission and scanning) microscopy. A neurulation overlap zone occupied this level. The dorsal portion of the neural tube formed by bending of the neural plate and approximation and fusion of neural folds (i.e., by primary neurulation), and the ventral part formed during secondary neurulation by cavitation of an initially solid, compact mass of cells, the medullary cord, derived from the tail bud. Secondary neurulation involved four morphogenetic processes: (1) segregation of the cells of the prospective medullary cord from cells of adjacent regions, (2) formation of a precisely delimited medullary cord, (3) cavitation of the central portion of this cord, and (4) coalescence of all lumina into a single, central cavity. Cell segregation was associated with the formation of a layer of primarily extracellular materials between adjacent organ rudiments. The source and composition of these materials are unknown. Formation of the medullary cord entailed considerable elongation of the peripheral cells of this developing structure and the fabrication of small intercellular junctions, first at the basal (outer) ends of the elongating peripheral cells, and then at their apical (inner) ends. These events resulted in the formation of an outer pseudostratified layer of radially arranged, columnar cells, having characteristics similar to those of the neural plate, and an inner cluster of irregularly shaped and arranged cells. Cavitation always occurred first at the junction between these two cellular populations. The central cells of the medullary cord also eventually elongated, like the peripheral cells, and may have been intercalated into the lateral walls of the developing neural tube as lumina coalesced.
The differential distribution of synaptic terminal on marginal and central cells in the cat medial superior olivary nucleus
Authors: Schwartz Ilsa R. 
Published: February 2005

AbstractElectron microscopic analysis of the perikaryal surfaces of central and marginal cells in the cat medial superior olivary nucleus has revealed three differences in their relationships with synaptic terminals. Marginal cells have a smaller percentage of their surface covered by synaptic terminals; synaptic endings on marginal cells tend to be smaller in size; and a higher proportion of synaptic terminals on marginal cells contain small vesicles. These differences suggest that central and marginal cells differ in the information which they receive, as well as in the cells to which they pass their information.
Innervation of rabbit fetal lungs
Authors: Hung Kuen‐Shan 
Published: February 2005

AbstractNerve fibers, autonomic ganglia, and neuroepithelial bodies of the lungs of rabbit fetuses, 17 to 31 days gestational age, were studied with neurohistological techniques including silver impregnation, acetylcholinesterase histochemistry, and glyoxylic‐1acid‐induced histofluorescence for monoamines.The silver impregnation method showed that nerve fibers and ganglia accompanied the bronchi and large pulmonary blood vessels to enter the developing lungs by the 17th day of gestation. Cholinergic and adrenergic nerves began to appear in the walls of the bronchi on the 21st day. The developing pulmonary arteries had accompanying adrenergic nerves on the 25th day. Acetylcholinesterase‐positive parasympathetic ganglia were seen on the 27th day. Silver‐impregnated nerve fibers in the developing alveolar walls and pleura were found on the 25th day.Neuroepithelial bodies and specialized single cells which were argyrophilic, acetylcholinesterase‐positive, and fluorescent could be demonstrated in 19–21‐day‐old and older fetuses; and some of these structures were innervated by sensory and autonomic motor fibers. These observations indicated that nervous tissue and neuroepithelial bodies appeared in the lungs during the glandular stage of the lung development and that differentiation of adrenergic and cholinergic nerves began in the late glandular stage.
Precocious development of granular convoluted tubules in the mouse submandibular gland induced by thyroxine or by thyroxine and testosterone
Authors: Gresik E. W. , Barka T. 
Published: February 2005

AbstractThe effects of the administration of thyroxine (T4) and/or testosterone (TP) on the early postnatal differentiation of granular convoluted tubule (GCT) cells of the submandibular glands were studied in Swiss‐Webster mice. From birth, mice were injected daily with T4 up to the time of killing at 15 or 20 days of age. In addition, groups of mice were given one injection of TP eight days before killing. Control animals received vehicles (saline and/or sesame oil). Sections of the glands were stained with toluidine blue, or immunocytochemically by the unlabelled antibody enzyme method, for the localization of protease A, epidermal growth factor, or renin. Supernatants of the gland were analyzed for protease activity (pH 8.5, substrate: tosyl‐glyclyl‐L‐prolyl‐L‐arginine nitroanilide acetate), or by radioimmunoassay for EGF content. At 15 days of age no GCT cells were present in the glands of control or TP‐treated mice. In T4‐injected mice many small GCT cells occurred, while larger and more numerous GCT cells were seen in the glands of mice that received both hormones. TP alone had no effect on levels of EGF or protease activity. In T4‐treated mice, protease levels increased 10‐fold and EGF content rose 28‐fold. TP administration to T4‐treated mice caused a further threefold, increase in both protease activity and EGF content. At 20 days of age the glands of control mice had a few small GCT cells, and both protease activity and EGF content were substantially increased. TP treatment was again without effect. However, daily injections of T4 caused both protease activity and EGF levels to increase 20‐ and 11‐fold, respectively. Just as in 15‐day‐old mice, TP administration to T4‐primed mice resulted in further increases in the two polypeptides. Immunocytochemical staining for protease A and EGF confirmed the chemical data. Renin was detectable immunocytochemically at both ages in the glands of mice that had received T4, but it was seen in the glands of mice that had received TP alone only at 20 days of age. It is concluded that T4 caused a precocious induction of GCT cells and their specific products. Although TP alone had no effect on their early differentiation, it acted synergistically with T4 in inducing GCT cells. There were no obvious sex differences in any of these features in control or treated animals.
The median eminence in normal, ovariectomized, and ovariectomized‐estradiol‐treated hamsters: An ultrastructural study
Authors: Merchant Randall E. , Dollar James R. 
Published: February 2005

AbstractIn an effort to define more clearly the effect various plasma concentrations of estrogen have on the morphology and function of tanycytes, the present investigation examined the median eminence (ME) of normally cycling, ovariectomized, and ovariectomized‐estradiol‐treated hamsters. In normally‐cycling animals, when endogenous estrogen was at its highest level (day 4 or proestrus), numerous microappendages arose from the luminal surfaces of tanycytes located in the ventrolateral region of the ME. Large blebs (1.0–5.0‐μm diameter), miniblebs (1.0‐μm diameter), and microvilli dominated the surfaces of these cells. Large blebs appeared to have been formed by the coalescence of several miniblebs and were composed of cytoplasmic ground substance devoid of organelles. The peduncular shape of many of these blebs suggested their involvement in an apocrinelike secretion by the tanycyte. When endogenous estrogen levels were low (day 1 of the estrous cycle), the tanycytes of normally cycling hamsters possessed slightly fewer microappendages. Following ovariectomy, large blebs were nearly absent from the luminal surfaces of tanycytes, and the number of miniblebs and microvilli were also greatly reduced. Subcutaneous injections of 17‐beta estradiol benzoate restored the large blebs to the tanycyte surface. The number and variety of tanycytic microappendages in these animals resembled those in normally cycling hamsters on day 4 of the estrous cycle. The present study demonstrates that tanycytes of the hamster ME are sensitive to estrogen and vary in their morphology in relation to the animal's reproductive status. These changes in tanycyte morphology can be correlated directly to functions of absorption (microvilli) and secretion (blebs). The sensitivity of tanycytes to estrogen suggests that these cells may also play a role in the hypophyseal‐ovarian feedback mechanism.
Structural characteristics of the corpus luteum during implantation in the rhesus monkey (Macaca mulatta)
Authors: Booher Carolynn , Enders Allen C. , Hendrickx Andrew G. , Hess David L. 
Published: February 2005

AbstractCorpora lutea were obtained from ten pregnant rhesus monkeys during implantation, and the ultrastructure of granulosa and theca lutein cells was characterized. Specimens were individually staged with regard to the extent of implantation and the relationship to the rise in circulating progesterone and estrogen which is characteristic of early pregnancy. Structural changes characteristic of granulosa lutein cells occurring during implantation included: change in form of endoplasmic reticulum from predominantly agranular tubules to predominantly granular cisternae; reduction in size and number of lipid droplets; increase in area occupied by the Golgi and increase in length of the cisternae of the Golgi complex; development of numerous microvillus‐lined intracellular spaces; increase in numbers of membrane‐bound dense bodies including peroxi‐somelike bodies, multivesicular bodies within lobopodia, and other lysosomelike bodies; and alterations of mitochondrial cristae. These changes were suggestive of the production of a secretory protein, rapid utilization of existing steroid precursor reserves for the production of progesterone, and a reduction in capability for steroid precursor accumulation and processing by granulosa lutein cells. Structural changes characteristic of theca lutein cells occurring during implantation included an increase in size and number of lipid droplets, an increase in agranular endoplasmic reticulum, and an increase in area occupied by the Golgi complex. These changes were suggestive of an increased capability for steroid precursor accumulation and processing, perhaps for estrogen production, by the theca lutein cells.
The stem‐cell zone of the small intestinal epithelium. II. Evidence from paneth cells in the newborn mouse
Authors: Bjerknes Matthew , Cheng Hazel 
Published: February 2005

AbstractThe restriction of Paneth cell formation to the top of the Paneth cell distribution in the adult was suggested to be due either to the existence of a stem‐cell zone or to the influence of a Paneth cell population‐density gradient (Bjerkness and Cheng, 1981). To distinguish between the two possible mechanisms, the development of the Paneth cell distribution in neonatal mice (0–10 days old) was studied. If restricted formation were due to the presence of a population‐density gradient of Paneth cells, then in neonatal animals, in the absence of a Paneth cell population‐density gradient, Paneth cell formation would occur throughout the crypt base. If, on the other hand, restricted formation were due to the presence of a stem‐cell zone, and if this mechanism were operative in the newborn, Paneth cell formation in the newborn would be restricted to the region above the stem‐cell zone. The position of each Paneth cell within the crypt, and the size of its largest granule, were recorded. On day 0, Paneth cells were present, but crypts were poorly developed and positional assignment was not possible. On day 1, immature crypts developed. All Paneth cells found in immature crypts on day 1 were at the crypt‐surface junction (approximately position 5). On day 2, most Paneth cells were at the crypt‐surface junction. Thereafter, Paneth cells began to appear at lower positions. On day 3, there were 15 times more Paneth cells in position 5 than in position 1. On day 4, there were still three times more Paneth cells in position 5 than in position 1. With age, the proportion of Paneth cells in position 1 increased while that in position 5 decreased. On day 10 there were more Paneth cells in position 1 than in 5. At all time intervals, granules of Paneth cells in position 1 were significantly larger than those in position 5, indicating that Paneth cells in position 1 were older than those in position 5. It was concluded that in the neonate, before the establishement of a Paneth cell population‐density gradient, Paneth cell formation was restricted to positions 5 and above. This supports the existence of a stem‐cell zone, not a Paneth cell population‐density gradient, as the underlying mechanism of restricted Paneth cell formation in the adult.
A fine‐structural survey of the pulpal innervation in the rat mandibular incisor
Authors: Bishop M. A. 
Published: February 2005

AbstractThe innervation of the rat incisor pulp has been studied using transmission electron microscopy and light microscopy. Transverse sections of mandibular incisor pulp (380–460 gm rats) from numerous positions in the long axis of the tooth were examined systematically in the electron microscope. Quantitative data on total axon populations were obtained. The nerve fibers were found to pass through the lingual half of the pulp from the apical end to within 2 mm of the incisal tip. Although the nerve fibers were seen to lie amongst the connective tissue cells between the blood vessels, the electron microscopic observations showed that the blood vessels are not innervated. Throughout their pulpal course the nerve fibers showed no trace of perineurial investment. Virtually all the axons were unmyelinated. Total numbers of axons were small (233–328) and peak diameters of 0.3–0.4 μm confirmed the observed immature appearance of the nerve supply. Obvious nerve endings were seldom observed and the axons showed no structural association with odontoblasts. The evidence indicates that, although most axons terminate near the incisal end of the tooth, no specific structure is supplied. The qualitative features of the axons do not suggest autonomic function; however, they are consistent with a sensory role.