bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane modifications in chick osteoclasts revealed by freeze‐fracture replicas
Authors: Akisaka Toshitaka , Yoshida Hisaho , Kogaya Yasutoku , Kim Songchol , Yamamoto Masao , Kataoka Katsuko
Published: February 2005

Remarkable differences among various membranes of bone cells became evident by examination of freeze‐fracture replicas. In osteoclasts, three types of intramembranous particles (IMPs) were identified based on their size and shape: two sizes of isolated globular particles (8 and 12 nm in diameter) and rod‐shaped, linear aggregates (8 × 30 nm in dimension). Furthermore, the density and distribution pattern of these IMPs enabled us to distinguish three different domains of membranes of osteoclasts including reffled border, clear zone, and basolateral regions, as were also observed in thin sections. The highest density of IMPs was 3,500‐4,000/μm2 in the ruffled border membrane, and these IMPs included linear aggregates among the usual globular particles. Linear aggregated particles were also observed in the membrane of cytoplasmic vesicles in the vicinity of the ruffled border region, but not in this membrane in other bone cells. In attached osteoclasts, the distribution pattersn and densities of IMPs in each ruffled‐finger and ‐plate were extremely variable, from closely to the loosely packed membrane particles. Focal aggregates of membrane particles were also frequently encountered. An important outcome of the present study was the finding that the presence of linear aggregated particles proved to be an additional criterion for distinguishing membrane domains in freeze‐replicas of osteoclasts. The surface of the clear zone membrane was not smooth in profile, but revealed a number of eminences that were almost free of particles. Basolateral membranes exhibited a particle density of 2,400/μm2. Globular particles were homogeneously scattered in random fashion on their exposed fracture faces. In some cases, aggregates of IMPs on the basolateral membranes were encountered. In comparison with the ruffled fingers, microprojections from the basolateral surface showed a lesser density of IMPs and were devoid of rod‐shaped or linear aggregated particles. Differences between osteoblasts and osteocytes were apparent in the density and the size of IMPs. The membranes of osteoblasts and osteocytes contained the same types of globular particles as seen in osteoclasts. Various sizes of gap junctions were located only on basolateral membranes of the osteoblasts. In contrast, no cellular junctions were observed between osteoclasts and any other type of cells.
Spatial differences of endogenous lectin expression within the cellular organization of the human heart: A glycohistochemical, immunohistochemical, and glycobiochemical study
Authors: Bardosi A. , Bardosi L. , Hendrys M. , Wosgien B. , Gabius H‐J.
Published: February 2005

Protein‐carbohydrate recognition may be involved in an array of molecular interactions on the cellular and subcellular levels. To gain insight into the role of proteins in this type of interaction, surgically removed specimens of human endomyocardial tissue were processed for histochemical and biochemical analysis. The inherent capacity of these sections to bind individual sugar moieties, which are constituents of the carbohydrate part of cellular glycoconjugates, was assessed using a panel of biotinylated neoglycoproteins according to a standardized procedure. Together with appropriate controls, it primarily allowed localization of endogenous lectins. Differences in lectin expression were observed between layers of endocardial tissue, myocardial cell constituents, connective‐tissue elements, and vascular structures. The endocardium proved to be positive with β‐galactoside‐bearing probes; with neoglycoproteins carrying β‐xylosides, α‐fucosides, and galactose‐6‐phosphate moieties; and with probes containing a carboxyl group within the carbohydrate structure, namely sialic acid and glucuronic acid. In contrast, only fucose‐and maltose‐specific receptors were apparent in the elastic layers of the endocardium. Aside from ascertaining the specificity of the protein‐carbohydrate interaction by controls, i.e., lack of binding of the probe in the presence of the unlabelled neoglycoprotein and lack of binding of the labelled sugar‐free carrier protein, respective sugar receptors were isolated from heart extracts by using histochemically effective carbohydrates as immobilized affinity ligand. Moreover, affinity chromatography using immobilized lactose as affinity ligand as well as the use of polyclonal antibodies against the predominant β‐galactoside‐specific lectin of heart demonstrated that the lactose‐specific neoglycoprotein binding was due to this lectin. Remarkably, the labelled endogenous lectin, preferred to plant lecins for detecting ligands of the endogenous lectin, localized ligands in tissue parts where the lectin itself was detected glycohistochemically as well as immunohistologically. This demonstration of receptor‐ligand presence in the same system is a further step toward functional assignment of the recorded protein‐carbohydrate interaction. Overall, the observed patterns of lectin expression may serve as a guideline to elucidate the precise physiological relevance of lectins and to analyze pathological conditions comparatively.
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

Embryonic 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

In 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

Male 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

The 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

In 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

Male 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

Ultrastructural 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

The 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

The 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

Relaxin 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

Maxillary 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

In 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

The 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.
Cytoarchitectural reorganization of rabbit colonic goblet cells during baseline secretion
Authors: Radwan Khaled A. , Oliver Mary G. , Specian Robert D.
Published: February 2005

Light and electron microscopy were coupled with point counting methods to quantitate shape and volume changes of goblet cells during their migration and maturation from the base of the crypt to the colonic surface epithelium in the rabbit. After differentiation, goblet cells attain a broad pyramidal configuration in the basal third of the crypt. The cells elongate and dramatically decrease in volume as they move into the surface epithelium. The distributions and volume fractions of organelles were found to vary considerably, depending on the location of the goblet cell in the epithelium. Mucin granules are initially synthesized throughout the cytoplasm, but become increasingly concentrated as the cell matures. Organelles involved in synthesis such as the Golgi apparatus and rough endoplasmic reticulum (RER) similarly attain a more concentrated arrangement as the cell moves up in the crypt. The mean cell volume decreases from 1,228.8 μm3 for cells in the basal third of the crypt to 541.3 μm3 for goblet cells on the surface. Most organelles decrease in proportion to this decrease, although a disproportionately large decrease in the RER was measured. When actual subcellular volumes are calculated, a net decrease in several subcellular compartments is detected. This loss of granules and organelles is accomplished by the continual synthesis and secretion of mucin granules. Cytoplasm and organelles become entrapped in the upward movement of granules towards the cell apex, become irretrievably isolated, and are sloughed into the crypt lumen. This process accounts for the decrease in cell volume and contributes to the altered cytoarchitecture of the cell.
Spontaneous or experimentally induced formation of a special zone in the adrenal cortex of the adult brush‐tailed possum (trichosurus vulpecula)
Authors: Kerr J. B. , Weiss M.
Published: February 2005

The cytology and ultrastructure of the hypertrophied special zone, which is formed spontaneously in the adrenal cortex of adult female brush‐tailed possums (Trichosurus vulpecula), was compared to the adrenocortical tissue in adult males in which the special zone, normally absent, was induced following castration alone or by additional treatment with folliclestimulating hormone (FSH).

The special zone in females was situated between the zona fasciculata and the zona reticularis, the latter being a rudimentary zone in this species. Special zone tissue extended as a broad band parallel to and on one side of the adrenal medulla. In the luteal phase of the reproductive cycle, the special zone cells showed ultrastructural features commonly associated with steroidogenic tissues, with many mitochondria and compact masses of smooth endoplasmic reticulum. Cytoplasmic lipid inclusions were rarely observed. In lactating females, however, the special zone cells exhibited cytological and ultrastructural features suggestive of a transformation in their morphology broadly divided into two types of cells: (1) cells at the periphery of the special zone (closest to the zona fasciculata) showed variable quantities of lipid inclusions, mitochondria with dispersed cristae, and segregation of the smooth endoplasmic reticulum into compact masses; (2) cells within the more central regions showed an increasing abundance of lipid inclusions which in many cells became the dominant feature of the cytoplasm. These special zone cells contained very little smooth endoplasmic reticulum and their mitochondria contained few cristae together with amorphous granular material within the matrix.

In castrated males, special zone tissue developed between the zona fasciculata and the zona reticularis, appearing initially as focal islands of cells (8 months postcastration) and later (11 months postcastration) expanding into a single zone, probably via the proliferation and differentiation of adjacent cells of the zona fasciculata and longitudinal growth of the special zone. Similar focal aggregations of special zone cells were induced after 14 days of FSH treatment given to 2‐month castrated males. In all castrated and FSH‐treated castrated males, the ultrastructure of special zone cells was similar to that of special zone cells in luteal‐phase female possums.

The findings suggest that the formation and cellular composition of the special zone is associated with changes in the pituitary‐gonadal axis and that FSH plays a primary role in the differentiation of this tissue.
Branchings and course of the larger ducts and accompanying structures within the rat submandibular salivary gland
Authors: Lorber Mortimer
Published: February 2005

In the rat submandibular gland, the larger ducts, vessels, and AUtonomic elements are surrounded by appreciable collagen to form an extensive, ramifying core for the bulk of the parenchyma. This entity is analogous to the armature within a clay sculpture becAUse it provides a framework supporting softer surroundings. Its largest portion, the trunk, begins dorsorostrally at the hilus. Along its cAUdal course, the trunk emits limbs that, in turn, branch. Rostrally, the trunk and major limbs have their greatest diameters and contain lymphatic vessels and AUtonomic ganglia that are fewer or absent in the smaller divisions. Four to six orders of branching commonly occur. This architectural device constitutes a physical gradient which peaks at the hilus and is minimal where its components undergo the transition to the lobular parenchyma. The presence of an appreciable amount of connective tissue, nerves, and larger vessels would make this entity firmer than the highly hydrated parenchyma. The major divisions of this grouping are contacted by septa that extend from the organ capsule and demarcate lobules into which smaller divisions penetrate. The parenchyma is consequently ensconced between several strong structures containing abundant connective tissue. The dense collagen encompassing individual components of the biological armature would stabilize duct epithelium and its intercellular channels as well as brace vessels' walls. As a result of this architectural arrangement, the patency of all acinar, duct, and vascular structures is likely to persist despite neck and jaw movements that would otherwise distort them and thus hinder the formation and flow of saliva during feeding. This mechanism may be widespread among organs.
Immunohistochemical studies of the extracellular matrix in the condylar cartilage of the human fetal mandible: Collagens and noncollagenous proteins
Authors: Ami Yechiel Ben , Von Der Mark Klaus , Franzen Ahnders , De Bernard Benedetto , Lunazzi Gian Carlo , Silbermann Michael
Published: February 2005

This study provides data concerning the cells and their extracellular matrix in prenatal human mandibular condylar cartilage. The latter cartilage represents a secondary type of cartilage since it develops late in the morphogenesis of the craniofacial skeleton. The cartilage of the mandibular condyle is actively involved in endochondral ossification, thus showing all the phases of cartilage growth, maturation, and mineralization that precedes de novo bone formation. The present study focused on the localization and distribution of the major macromolecules that are normally encountered in cartilage and bone, including colagens, proteoglycans, fibronectin, osteonectin, osteocalcin, alkaline phosphatase, and anchorin CII. It became clear that the mineralized zone of the cartilage already contained bone‐specific antigens; thus the above zone might serve as an essential propagative predecessor in the ossification process.
Immunohistochemical localization of atrial natriuretic peptide in the developing and adult mammalian kidney
Authors: McKenzie James C. , Scott Jane N. , Inagami Tadashi
Published: February 2005

The discovery, within the last decade, of atrial natriuretic peptide (ANP), a family of peptides with natriuretic/diuretic and vasorelaxant properties, has prompted much research into the mechanisms and sites of action of ANP within the kidney. In the present study, ANP was localized in the kidneys of several mammalian species by immunohistochemical techniques (1) to identify possible sites of synthesis; (2) to compare the localization of ANP to known physiological effects; (3) to determine species differences, if any, in ANP localization; and (4) to study the development of ANP immunoreactivity in the fetal and neonatal rat kidney. Using an antibody against rat ANP IV, ANP was localized exclusively on the proximal convoluted tubule (PCT) brush border and within intercalated cells of the outer medullary and cortical collecting tubules and ducts of adult mouse, rat, pig, monkey, and human kidneys. The development of ANP immunoreactivity paralleled the differentiation and maturation of collecting duct epithelium in rat fetal kidney. Atrial natriuretic peptide found within intercalated cells of the cortical and outer medullary collecting ducts may be the result of endogenous synthesis and, following secretion, may be available to receptors in the inner medullary collecting ducts.
Development of anencephaly and its variants
Authors: Müller Fabiola , O'Rahilly Ronan
Published: February 2005

Extreme variants of anecephaly in two human embryos of the same stage, namely 22 (54 days), shed new light on problems such as craniocerebral interrelationships and the timing of developmental events. Embryo X had a chondrocranium that possessed features typical of a holoacranial anencephalic skull and an extremely well‐preserved brain, in which some of the neural tracts were comparable to those in a normal control. On the other hand, embryo Y of the same stage had a completely degenerated brain, although the chondrocranium was more nearly normal and represented the precursor of a meroacranial skull. A comparison of the two cases seems to indicate a certain independence between skull and brain. Moreover, it appears possible that the disturbances are related primarily to the skeletal, and only secondarily to the nervous, component. Comparisions with experimental data allow the conclusion that the maldevelopment involves mostly paraxial mesenchyme and little or no disturbance of neural crest. The timing of the mesenchymal defect is probably as early as stages 8 and 9 (18–20 days). This is also the time at which mesenchymal defects can result in failure of the neural tube to close.
Renal morphology of the hook‐lipped african rhinoceros, Diceros bicornis, linnaeus
Authors: Maluf N. S. R.
Published: February 2005

The kidney of Diceros bicornis has about 60 lobes, all appearing peripherally. These are separated by interlobar septa, except for small septal defects through which tubules pass. Renal capsule and interlobar septa are fibromuscular and contain small blood vessels. The kidney is about 65% cortex. It contains about 12.5 × 106 glomeruli, which form about 7% of the cortical mass and 4.6% of the renal mass. Diameter of a glomerular capsule is about 244 μm, there being no difference in size across the cortex in these adults. The ureter bifurcates into a cephalic and a caudal, fibromuscular, urothelial‐lined conduit, into which open about 23 urothelial‐lined infundibula. The common large collecting duct, or tubus maximus, of every lobe opens at the apex of its infundibulum. Two tubi may join into one infundibulum. The tubi and their terminal collecting ducts (of Bellini) are part of the inner medulla. Musculature of conduits and infundibula is largely longitudinal. The calyx may be represented by a circular muscle bundle near the apex of every infundibulum. The large intralobar veins are partly adherent to their infundibulum and calyx and receive arcuate veins via valved orifices. Most branches of the renal artery enter via the interlobar septa. Within a septum they branch again and also supply numerous perforators, which thence enter the cortex. Remaining branches of the renal artery enter cortex directly from without. A fibromuscular scaffolding lies deep to arcuate veins where they contact medulla. Where these veins contact cortical tubules; however, their walls become merely endothelium, like the walls of the interlobular veins.
Quantitative changes in steroidogenic organelles in the corpus luteum of the pregnant rat in relation to progestin secretion on day 16 and in the morning and afternoon of day 22
Authors: Dharmarajan A. M. , Bruce Neville W. , Waddell Brendan J.
Published: February 2005

The present study was carried out to determine whether the major steroidogenic organelles of luteal cells quantitatively reflect variations in ovarian steroid secretion rates during pregnancy in the rat. Assessments were made on day 16 and in the morning (AM) and afternoon (PM) of day 22 (term is day 23). Ovarian steroidogenesis differs both quantitatively and qualitatively between these stages of pregnancy, so together they provide an ideal physiological model to study structural‐functional relationships in the ovary. Corpora lutea of five rats were examined at each stage after progesterone and 20α‐hydroxypregn‐4‐en‐3‐one (20α‐OHP) secretion rates had been determined by a venous outflow technique. Total progestin secretion (progesterone plus 20α‐OHP) fell from 32.5 ± 5.2 to 9.8 ± 1.2 μg/hr per ovary (mean ± SEM) between day 16 and day 22 AM but then increased to 22.6 ± 1.4 μg/hr per ovary by day 22 PM. The total volume of luteal cell cytoplasm was slightly greater at day 22 AM and PM than at day 16. Similarly, the volumes of smooth endoplasmic reticulum (SER), lipid droplets, and membrane‐bound granules all increased, but the volume of mitochondria decreased slightly. In contrast, the surface areas of SER and the inner and outer mitochondrial membranes did not change between day 16 and day 22 AM but then increased substantially by day 22 PM. Therefore, steroid secretion rates per unit area of steroidogenic membrane showed no consistent pattern over the stages examined. Thus these data do not support the existence of a consistent structural‐functional relationship over the normal range of secretory activity in the rat corpus luteum. It is likely that a number of factors, including a variable reserve capacity for steroidogenesis and secretion of nonsteroid hormones, contribute to this inconsistency.
Fine structural changes and lysosomal phosphatase cytochemistry of ameloblasts associated with the transitional stage of enamel formation in the rat incisor
Authors: Salama Ahmed H. , Zaki A. E. , Eisenmann Dale R.
Published: February 2005

Trimetaphosphatase (TMPase) and cytidine‐5′‐monophosphatase (CMPase) were used as lysosomal markers in the transitional ameloblasts (TA) to investigate the distribution of lysosomal structures and to correlate the cytochemical findings with the ultrastructural features of these cells. Of particular interest were the cytochemical and morphological changes which occur as the ameloblasts approach the maturation stage of enamel formation. The sequence of changes observed provides a basis for designation of three regions of the transitional zone (early and late TA and modulating ameloblasts). In the early TA region, the cells decreased in height and contained phagic vacuoles as well as numerous TMPase and CMPase reactive structures. Late transitional ameloblasts had invaginations at their distal ends as well as membrane‐bound structures, both filled with fine granular material. Dense bodies, phagic vacuoles, and other elements of the lysosomal system were enzyme reactive. Modulating ameloblasts lacked the phagic vacuoles but exhibited large numbers of multivesicular bodies, vesicles, and secretory granules. Their distal ends were morphologically altered indicating a change towards ruffle‐ or smooth‐ended varieties of maturation ameloblast. In the former, increased granular material was observed within cell membrane invaginations and associated membrane‐bound structures. In the latter, intercellular spaces widened and were filled with granular material. The present cytochemical findings of an extensive lysosomal system in transitional ameloblasts confirm the function of those cells in reducing the secretory ameloblast population and in the selective elimination of their protein‐synthesizing organelles. Furthermore, this extensive lysosomal system and the present morphological findings are consistent with a potential role for transitional ameloblasts in contributing to the marked loss of enamel protein known to occur during maturation.
Post‐hatching development of the thymic epithelial cells in the rainbow trout Salmo gairdneri: An ultrastructural study
Authors: Castillo A. , López‐Fierro P. , Zapata A. , Villena A. , Razquin B.
Published: February 2005

This study reports the ultrastructure of subpopulations of epithelial cells of the thymic parenchyma during the post‐hatching development of the rainbow trout, Salmo gairdneri, kept at 14°C. At hatching, the thymus contained a small number of medium and large thymocytes interspersed among three different types of epithelial cells: (1) epthelial cells adjacent to the connective tissue capsule; (2) ramified dark epithelial cells with electron‐dense cytoplasm; and (3) pale electron‐lucent epithelial cells displaying secretory‐like features. All these cell types were anchored to one another by desmosomes and had apparently differentiated from the pharyngeal epithelium. At 4 days after hatching, the thymus enlarged, and numerous gaps occurred between the cell processes of contiguous epithelial cell processes of contiguous epithelial cells adjacent to the capsular connective tissue. In 21‐day‐old trout, thymic trabeculae developed carrying blood vessels, and a subcapsular zone became evident containing lymphoblasts and large subcapsular epithelial cells. In 30‐day‐old trout, an outer thymic zone developed consisting of spindle‐shaped epithelial cells which formed a dense network. At this stage, scattered cystic cells, which apparently differentiated from the pale epithelial cells, were present.
Dermal ridge development on the volar pads of the rat (Rattus norvegicus) and comparative study of pattern formation using inbred strains
Authors: Okajima M.
Published: February 2005

The development of dermal ridges, ridge configurations, and volar pad contours was investigated in the volar skin of the rat (Rattus norvegicus). The ridged structures corresponding to the epidermal ridges of primates exist only at the epidermal‐dermal junction in the rat. Dermal specimens were prepared by treatment with alkaline solution and examined by toluidine blue staining and scanning electron microscopy, together with histological sections. Differentiation of dermal ridges began on day 18 of gestation on the palm followed by the sole. Ridges incresed in number with advancing age. The process was complete approximately 2–3 days after birth, and sweat ducts began to develop simultaneously. As dermal ridges present various configurational patterns on palmar interdigital pad III, pattern formation on this pad was inspected in fetuses of three inbred strains possessing different pattern types, and in the hybrid progeny derived from them. Patterns and pad forms appeard to be under genetic control. It was revealed that the ridge arrangements, i.e., whorls, triradii, comb‐like patterns, and others, are closely related to the pad contours during the developmental period, as hypothesized in primates.