bluuebunny/crossref_metadata_2025_split huggingface dataset:
New insights on the mechanism of testis differentiation from the morphogenesis of experimentally induced testes in genetically female chick embryos
Authors: Maraud Roland , Vergnaud Odile , Rashedi Michel 
Published: February 2005

AbstractEmbryonic testes grafted in the extraembryonic coelom of 3‐day‐old genetically female chick embryos may induce total and definitive reversal of gonadal sex differentiation. In this experimental condition, the left gonad becomes a testis instead of an ovary. This makes it possible to compare testicular and ovarian morphogenesis in animals having the same genetic sex and to discount what is due to differences in the genetic determination between male and female.The morphogenesis of such testes is marked by a disappearance of the cortical germinal epithelium. The medullary sex cords keep a narrow lumen instead of becoming large lacunae. The germ cells remain few in the sex cords and do not become meiotic. Furthermore, interstitial cell development is known to be very slow. As a consequence the gross size of the gonad is much smaller than that of an ovary. All these morphogenetic phenomena are unlike those observed during normal ovarian differentiation and evidence an inhibiting influence of the grafted testes. Since inhibition and masculinization are concomittant, inhibition appears to be the mechanism responsible for gonadal sex reversal.The extraembryonic situation of the grafted testes and their relation with the embryo only via the blood stream demonstrates the role of a secreted substance or substances still to be exactly identified. Previous data suggest that this could be the anti‐Müllerian‐hormone (AMH).Furthermore, previous and present results show that testis differentiation can be actively induced in a bird. This does not agree with the hypothesis that the gonads of the homogametic sex, i.e., the testes in birds, do not need any inducer in order to differentiate.The similarity between chronological and structural events of morphogenesis in experimentally induced and normal testes suggests that both result from the same inhibitory mechanism.
Three structures associated with the nucleolus in male rat germinal cells: Round body, coiled body, and “nubecula” and general presence of round body at male meiosis
Authors: Schultz Michael C. , Leblond C. P. 
Published: February 2005

AbstractIn addition to chromosomes and nucleoli, three structures, i.e., round body, coiled body, and nubecula, are encountered in the nucleus during the meiotic prophase in male rats. These structures have been examined by electron microscopy in random and serial sections.The round body is a finely fibrillar, proteinaceous structure closely associated with the granular component of a nucleolus in rat spermatocytes and young spermatids. A similar structure has been observed in man, the monkey Macaca mulatta, the gastropod Achatina fulica, and the insect Locusta migratoria. Together with evidence from the literature, these results support the view that the round body is of general occurrence in the male meiocytes of eukaryotes and may, therefore, play a role in meiosis.The coiled body is a group of electron‐dense elements called “coils”, which average 35 nm in width, except after mid‐pachytene when their size almost doubles. The coils are composed of 2‐nm‐wide filaments and 8 to 10‐nm‐wide granules, both of which are ribonucleoprotein. The coiled bodies are interpreted to be groups of “spliceosomes”, that is, structures containing heterogeneous RNA and small nuclear RNA. A remarkable feature of the coiled body is its temporary disappearance at early pachytene and its reappearance at late pachytene, possibly due to drastic changes in the turnover rate of its component RNAs.The nubecula is a newly identified nuclear inclusion, composed of weakly staining threads loosely organized into a 560nm‐wide spheroid. It has been observed only in early pachytene nuclei.
Histologic changes in tissue components of the hyperplastic thyroid gland during its involution in the rat
Authors: Wollman Seymour H. , Herveg Jean Pierre , Tachiwaki Osamu 
Published: February 2005

AbstractMale Fischer rats were fed a low‐iodine diet containing thiouracil for 21 days to produce hyperplastic thyroid glands, and then fed a high‐iodine diet for various time intervals, from 5 hr to 180 days, in order to study the morphological changes that occur during involution. Thyroids were fixed by perfusion fixation and embeded in Epon. Sections were examined by light microscopy. Initially at 0 days of involution (at the time of the change to the high‐iodine diet), follicular lumens were very narrow and capillary lumens were verywide. The capsule was thick and infiltrated with mononuclear leukocytes. No obvious changes occurred for 1 day after the change in diet, but shortly thereafter capillary lumens began to narrow. By 4 days, most capillary lumens began to narrow. By 4 days, most capillary lumens were close to normal size; capillaries formed a more or less normal bed except that many were embedded in a relatively thick or wide interfollicular matrix. This matrix was largely gone by 21 days. Between 1 and 21 days, follicular lumens dilated progressively as colloid accumulated. The density of staining of the accumulated colloid varied from follicle to follicle, and this variation was also observed in older controls. Inflammatory cells gradually disappeared from the capsule and most were gone by 15 days. Starting at approximately 15 days and continuing to 180 days, one or more disintegrating cells were found in some lumen profiles. Colloid goiters were not observed in these rats even after several months of involution. Some lumens were rather large, however, and small fractions of the follicles, both small and large, were bounded by flat cells and resembled “cold” follicles morphologically.
Ultrastrutural changes in thyroid epithelium during involution of the hyperplastic thyroid gland
Authors: Tachiwaki Osamu , Zeligs Joseph D. , Wollman Seymour H. 
Published: February 2005

AbstractThe ultrastructure of the thyroid epithelial cell was examined at various time intervals after induction of involution of the hyperlastic thyroid gland. Thyroids were made hyperplastic by the feeding of thiouracil in a Remington low‐iodine diet to male Fischer rats for 3 weeks. Involution was induced by replacing the thiouracil‐containing diet with Purina Laboratory Chow, a high‐iodine diet. During involution, organelles that play a role in the synthesis and secretion of thyroglobulin, such as the rough endoplasmic reticulum, Golgi apparatus, and apical vesicales, were well preserved and prominent features of the epithelial cell. The apical plasma membrane of many cells was highly irregular for approximately 2 weeks with signs suggesting rapid discharge of apical‐vesical contents into the lumen of the follicle. Pseudopods and colloid droplets were present but were not very prominent features of the cell. No signs of extensive autophagy or obvious increased incidence of lysosomes were present, although there was an elevation in the incidence of small dense bodies starting about day 8, and prominent by 15 days. Some of these may be phagosomes formed from luminal debris. The observations indicate that in volution of the hyperplastic thyroid in which there is maintenance of the protein synthetic apparatus and little sign of autophagy or death of the epithelial cells is remarkably different from phenomena occurring during involution of prostate or mammary glands.
Comparison of a special class of epithelial cells in hyperplastic thyroids undergoing involution and in thyroids in hypophysectomized rats
Authors: Tachiwaki Osamu , Wollman Seymour H. 
Published: February 2005

AbstractIn male Fischer rats, a class of follicles with flat epithelium is present as a minor component of thyroid glands in which most of the follicles have cuboidal epithelium. These follicles occur in thyroids that have been made hyperplastic by feeding the rats thiouracil for 21 days and then allowing involution for 21 days or more. They also occur in older control rats. The follicles resemble in morphology, at the light‐microscope level, the so‐called “cold” follicles that occur in aged mice. We have examined the ultrastrucutre of the flat cells in these follicles and compared it with that of the flat cells occurring in the thyroid follicles of hypophysectomized rats. The cells in involution have abundant rough endoplasmic reticulum (RER) and few lysosomes and, in these respects, differ markedly from cells in hypophysectomized rats. The follicles with flat cells are surrounded by a normal incidence of blood capillaries, so that the cells do not appear to be deprived of access to an adequate supply of materials necessary to satisfy their metabolic requirements. Their abundant RER suggests that they have thyroid‐stimulating hormone (TSH) receptors, so that the flat cell may be the result of some process occurring at a step distal to receptor coupling with TSH. Their occurrence in young rats after the induction of hyperplasia may be a consequence of cell multiplication producing a clone of neighboring abnormal cells that have an abnormally small cell height.
Scleral calcification and photoreceptor cell death during aging and exposure to chronic stress
Authors: Keith O'Steen W. , Brodish Alvin 
Published: February 2005

AbstractMale and female Fischer 344 rats of three different ages (12, 18, and 25 months) have been examined for the presence of photoreceptor (PR) cell loss and for occurrence of scleral cartilage and bone formation. In addition, male and female rats, aged 11 months at the beginning of the experiments, were exposed to chronic stress for either 0.5, 2, 4, or 6 months. Photoreceptor cell death gradually increases during the aging process and is exacerbated by exposure to chronic stress. It is more severe in the peripheral than the central retina and exposure to stress increases this pattern of cell loss. The superior retina is more severely affected than the inferior hemisphere in aging and during stress. The incidence of scleral cartilage or bone formation increases with age in male and female rats, but with stress exposure an increase is seen in males only. Bone formations occur more frequently in male than in female animals and are almost always (97%) located in the superior hemisphere of the eye. Although there appears to be a direct relationship between photoreceptor cell death and the occurrence of scleral ossifications in group data, in individual eyes the bone formations are not always associated with severity of PR cell loss. The relationship of PR cell death and incidence of scleral ossification to gender and to exposure to stress supports a hypothesis for an endocrine basis of ocular aging.
The effects of colchicine on the ultrastructure of odontogenic cells in the common skate, Raja erinacae
Authors: Prostak Kenneth , Seifert Philip , Skobe Ziedonis 
Published: February 2005

AbstractUltrastructural alterations in duced by colchicine were investigated to determine the secretory activities of odontogenic cells during formation of tooth enameloid matrix in skates. Treated skate inner dental epithelial (IDE) cells did not display dilated cisternae of the granular endoplasmic reticulum (GER) nor accumulate Golgi‐associated secretory granules at any dose level or time interval examined. This response was markedly different from that observed in teleost IDE cells synthesizing the enameloid collagen matrix. Treated skate IDE cells did show increased accumulations of glycogencontaining vesicles and intercellular glycogen associated with amorphous material, compared to controls. Additionally, the aberrant occurrence of large intracellular glycogen pools and amorphous material suggested that carbohydrate processing was a major function of skate IDE cells.Treated odontoblasts associated with enameloid matrix formation sometimes showed dilated GER cisternae, but procollagen secretory granules were not obsered. Instead, electron dense material was present within the Golgi cisternae, tubular granules, and large granules. Some elecron‐dense material appeared to be shunted to a resorptive pathway via multivesicular bodies in treated odontoblasts. The continuity of tubular granules with the enameloid matrix suggested that they contained precursors of the enameloid matrix, and possibly the periodic, 17.5‐nm crossstriated, “giant” fibers.Treated odontoblasts associated with predentin collagen matrix deposition showed dilated GER cisternae and accumulations of procollagen secretory granules, features consistent with the function of active collagen synthesis and secretion.The findings indicate that (1) skate IDE cells do not synthesize enameloid collagen as found in bony fish tooth development; (2) skate IDE cells do process glycogen for secretion into the enameloid matrix; (3) collagen, although present, is not a major constituent of skate enameloid matrix; (4) enameloid “giant” fibers are unique to elasmobranchs; and (5) odontoblasts synthesize and secrete proteins other than collagen into the enameloid matrix.
The innervation of human teeth and gingival epithelium as revealed by means of an antiserum for protein gene product 9.5 (PGP 9.5)
Authors: Ramieri G. , Anselmetti G. C. , Baracchi F. , Panzica G. C. , Viglietti‐Panzica C. , Modica R. , Polak J. M. 
Published: February 2005

AbstractThe innervation of human teeth and oral mucosa has been studied in the past by different methods, none of which offered a clear description of the precise morphology of nerve fibers and terminals and of nerve organization as a whole. Recently, interesting findings have been obtained by means of immunohistochemical investigations for neurofilaments and S‐100 proteins. A new brain‐specific molecule, protein gene product 9.5 (PGP 9.5), has been used for the first time in the present research to investigate the distribution of nerves in human oral mucosa and decalcified teeth, about which there is a paucity of information. The data provided in this study, confirming previous work in other species, may be of value for understanding the anatomy of human oral innervation. In the oral mucosa, the antiserum labels nerve fibers, corpuscles, and neuroendocrine (Merkel) cells. In sections of decalcified teeth, numerous PGP 9.5 positive fibers are demonstrated in the pulp and in the inner 100 μm of dentin. The novel nerve tissue protein used, PGP 9.5, thus appears to be a reliable marker for studies of nerve fibers in human tissues and not to be affected by decalcification procedures. It could then be used for investigations on the innervation of normal and pathological calcified human tissues.
Cytokeratin expression in human tongue epithelium
Authors: Sawaf M. H. , Ouhayoun J. P. , Shabana A. H. M. , Forest N. 
Published: February 2005

AbstractThe epithelium of the human tongue shows diverse morphological variations from one site to another and even within the epithelium of the same papilla. This complexity has led to confusion regarding tongue epithelium as being orthokeratinized, parakeratinized, or nonkeratinized.Cytokeratins have been shown to characterize different epithelia. The present paper describes cytokeratin expression by adult tongue epithelia and relates their distribution to morphology. Six healthy human tongue specimens were obtained after plastic surgery and cytokeratin expression was investigated immunohistochemically, using a panel of 15 antibodies for cytoskeletal proteins, and biochemically using two‐dimensional gel electrophoresis.The results showed that the ventral and lateral surfaces of the tongue are related to the nonkeratinizing stratified squamous epithelia, esophageal type, whereas the dorsal surface showed mixed expression of cytokeratins. In the tip of filiform and on the surface of fungiform papillae, cytokeratins of terminal differentiation are expressed as skin type; and in the rest of the papillae as well as in interpapillary areas, the epithelium expresses esophageal type cytokeratins. Certain simple epithelial cytokeratins were found in taste buds. Cytokeratin 19 was also detected in the basal cell layer of all esophageal type epithelia in the tongue.The present results provide basis for studies on the biological events in epithelial differentiation during development and in pathology.
Ultrastructural morphology and relaxin immunolocalization in giant trophoblast cells of the golden hamster placenta
Authors: Johns T. C. , Renegar R. H. 
Published: February 2005

AbstractRelaxin immunoreactivity was previously demonstrated in three cell types within the hamster placenta; fetal primary and secondary giant trophoblast cells (GTCs) and maternal endometrial granulocytes. The objectives of the present research were to examine the ultrastructure of the GTCs and identify the intracellular relaxin storage site. Primary GTCs, first present on day 8 of gestation, were characterized by numerous polyribosomes and large heterogeneous cytoplasmic inclusions suggesting phagocytic activity. Primary and secondary GTCs from days 10, 14, and 15 of gestation contained numerous polyribosomes, mitochondria with tubular cristae, an extensive Golgi complex, and abundant rough endoplasmic reticulum, all characteristics of a cell actively involved in protein synthesis. Membranebound secretory granules were not present. Relaxin was immunolocalized within the Golgi complex of primary and secondary GTCs using the avidin‐biotin‐peroxidase method. Following differential centrifugation of hamster placental homogenates and radioimmunoassay (RIA) of subcellular fractions, the majority of relaxin immunoactivity was detected in the postmicrosomal fraction; however, the majority of relaxin immunoactivity from similarly treated pig corpora lutea was present in the mitochondrial/granule fraction. These data indicate that hamster placental relaxin is not stored in membrane‐bound secretory granules but is contained within the extensive Golgi complex of the GTC.
Distribution of 3H‐proline within transseptal fibers of the rat following release of orthodontic forces
Authors: Row K. L. , Johnson R. B. 
Published: February 2005

AbstractMaxillary right first molar teeth of rats were tipped mesially with an orthodontic appliance for 2 weeks (experimental group), 3H‐proline was injected, and orthodontic forces were removed 6 hr later (time 0). The contralateral molar teeth of treated (internal control group) and age‐ and weight‐matched untreated animals (external control group) were also studied. Diastemata were created between the molar teeth by the orthodontic appliance, and transseptal fibers between first and second (P<0.001) and second and third molars (P<0.005) were significantly lengthened as compared to external and internal controls at time 0. Diastemata between molar teeth were closed 5 days after removal of orthodontic force. Transseptal fibers adjacent to the source of the orthodontic force (mesial region) had the highest mean number of 3H‐proline‐labeled proteins at time 0 and at all times following removal of the force (P<0.001), and had the highest rate of labeled protein removal (P<0.001). Half‐lives for removal of 3H‐proline‐labeled transseptal fiber proteins were significantly greater in mesial and distal regions and significantly less in middle regions of experimentals than in corresponding regions of external controls (P<0.001). These data suggest the following: (1) transseptal fibers adjust their length by rapid remodeling in regions experiencing a tensile force; (2) collagenous protein turnover within the middle third of the transseptal fibers is more rapid subsequent to release of orthodontic force than during normal physiologic drift, suggesting that this region adapts rapidly to changes in adjacent tooth position and that these fibers do not play a significant role in relapse of orthodontically relocated teeth; and (3) significant differences in turnover rates of 3H‐proline‐labeled transseptal ligament proteins of external and internal control quadrants suggest that tooth movement produces both local and systemic effects on collagenous protein metabolism.
The effect of chronic hypercalcemia or hypocalcemia on the follicular and parafollicular cells in rat thyroid gland
Authors: Kališnik Miroslav , Zorc‐Pleskovič Ruda , Pajer Zdenka , Pavlin Katka 
Published: February 2005

AbstractIn three experiments of 30 weeks' duration, 93 adult female Wistar rats received controlled amounts of calcium with food and water, to produce a state of either hypercalcemia or hypocalcemia. A systematic sterological analysis of the thyroid glands and a radioimmunological analysis of thyroxine, triiodothyronine, and thyrotropine were performed. In the hypercalcemic rats, a reactive hyperplasia of the parafollicular cells was established; this was accompanied by morphological and biochemical signs of hyperfunction of the follicular cells, despite a reduced central stimulation by thyrotropin. In the hypocalcemic animals, no quantitative morphological changes in the parafollicular cells were observed; however, morphological and biochemical signs of hypofunction of the follicular cells were obvious, despite stronger central stimulation by thyrotropin. It is concluded that the extrinsic regulation of follicular cells by the blood calcium level is stronger than the intrinsic regulation by hypothalamo‐hypophyseal hormones.
Ultrastructure of the principal and accessory submandibular glands of the common vampire bat
Authors: Tandler Bernard , Toyoshima Kuniaki , Phillips Carleton J. 
Published: February 2005

AbstractThe principal and accessory submandibular glands of the common vampire bat, Desmodus rotundus, were examined by electron microscopy. The secretory endpieces of the principal gland consist of serous tubules capped at their blind ends by mucous acini. The substructure of the mucous droplets and of the serous granules varies according to the mode of specimen preparation. With ferrocyanide‐reduced osmium postfixation, the mucous droplets are moderately dense and homogeneous; the serous granules often have a polygonal outline and their matrix shows clefts in which bundles of wavy filaments may be present. With conventional osmium postifixation, the mucous droplets have a finely fibrillogranular matrix; the serous granules are homogeneously dense. Mucous cells additionally contain many small, dense granules that may be small peroxisomes, as well as aggregates of 10‐nm cytofilaments. Intercalated duct cells are relatively unspecialized. Striated ducts are characterized by highly folded basal membranes and vertically oriented mitochondria. Luminal surfaces of all of the secretory and duct cells have numerous microvilli, culminating in a brush borderlike affair in the striated ducts. The accessory gland has secretory endpieces consisting of mucous acini with small mucous demilunes. The acinar mucous droplets contain a large dense region; the lucent portion has punctate densities. Demilune mucous droplets lack a dense region and consist of a light matrix in which fine fibrillogranular material is suspended. A ring of junctional cells, identifiable by their complex secretory granules, separates the mucous acini from the intercalated ducts. The intercalated ducts lack specialized structure. Striated ducts resemble their counterparts in the principal gland. As in the principal gland, all luminal surfaces are covered by an array of microvilli. At least some of the features of the principal and accessory submandibular glands of the vampire bat may be structural adaptations to the exigencies posed by the exclusively sanguivorous diet of these animals and its attendant extremely high intake of sodium chloride.