bluuebunny/crossref_metadata_2025 huggingface dataset:
Light and electron microscopic examination of the mature decidual cells of the rat with emphasis on the antimesometrial decidua and its degeneration
Authors: Welsh Alerick O. , Enders Allen C.
Published: February 2005

Rat gestation sites were obtained on days 10 through 16 of normal pregnancy. Light and electron microscopic examination of day‐10 sites revealed a consistent complex pattern of stromal cell morphologies. Six distinct regions were identified: an antimesometrial region of epithelioid decidual cells that form the gestation chamber containing the embryo and extraembryonic membranes; an abembryonic antimesometrial decidual region, the decidual crypt, where the cells are separated by large extracellular spaces; a mesometrial region with granule‐containing cells and mesometrial decidual cells; a region of spiny cells that are lateral to the antimesometrial decidual cells and continuous with the mesometrial decidual cells; and a region of undifferentiated stromal cells adjacent to the myometrium. Between days 12 and 16, the antimesometrial decidua becomes thinner and is eventually sloughed into the newly formed uterine lumen. The role of the antimesometrial decidual cells is discussed with reference to trophoblast invasiveness, protein synthesis, and especially remodeling of the gestation chamber. Differences between decidua and deciduoma are considered.
Structure of taste buds in foliate papillae of the rhesus monkey, Macaca mulatta
Authors: Farbman Albert I. , Hellekant Göran , Nelson Adrienne
Published: February 2005

Taste buds in foliate papillae of the rhesus monkey were examined by electron microscopy. Three distinct cell types were identified. Type I cells were narrow elongated cells containing an oval nucleus, bundles of intermediate filaments, several Golgi bodies, and characteristic apical membrane‐bounded dense granules. These cells exhibited morphological variations: some had a moderately dense cytoplasm, perinuclear free ribosomes, and flattened sacs of rough endoplasmic reticulum; others had a more lucent cytoplasm, dilated irregular rough endoplasmic reticulum, lysosome‐like dense bodies, and lipid droplets. Type II cells typically contained a spherical, pale nucleus, a prominent nucleolus, supranuclear and infranuclear Golgi bodies, mitochondria with tubular cristae, and one or two centrioles. This cell type, too, showed some variation in the relative amounts of ribosomes and smooth endoplasmic reticulum, which varied inversely with each other. Type III cells were characterized by a clear apical cytoplasm essentially devoid of ribosomes and containing microtubules. In a few type III cells, the peri‐ and infranuclear regions contained many ribosomes and some rough endoplasmic reticulum. In most Type III cells, there were large numbers of dense and clear vesicles in the peri‐ and infranuclear regions; some of the vesicles were grouped in synapse‐like arrangements with adjacent nerves. The morphological variations exhibited by all three cell types could be accounted for by age differences in each of the cells. This would be consistent with the notion that cell renewal occurs in each of the three cell populations.
Ultrastructure of sertoli‐cell penetrating processes found in germ cells of the golden‐mantled ground squirrel (Spermophilus lateralis)
Authors: Vogl A. W. , Soucy L. J. , Foo V.
Published: February 2005

We have studied the ultrastructure of Sertoli‐cell processes that extend into developing germ cells of the ground squirrel (Spermophilus lateralis). In other mammals it is speculated that these processes anchor germ cells to the seminiferous epithelium and transfer materials between Sertoli and germ cells. In the ground squirrel, Sertoli‐cell projections first appear in round spermatids and consist of regions containing numerous mitochondria and intermediate filaments together with areas composed mainly of a fine filamentous matrix. Also present are what may be desmosomelike junctions with adjacent germ cells. During spermatogenesis, numerous changes in the penetrating processes and their internal composition occur. Especially significant are those occurring during the movement of residual cytoplasm basaly over spermatid heads: some Sertoli‐cell processes contain microtubules, mitochondria and vesicular elements, but also present are regions that lack organelles and appear simply as thin lamellae of cytoplasm that line cavernous invaginations of the germ cell. Coated vesicles and pits are present in processes and adjacent germ‐cell regions at all stages of spermatogenesis. Our observations are consistent with the suggestions that Sertoli‐cell processes have an attachment function and that they also may facilitate the movement of residual cytoplasm into the epithelium. Further, they indicate that these structures might be involved with receptor‐mediated edocytosis.
Retinofugal projections of the big brown bat, Eptesicus fuscus and the neotropical fruit bat, Artibeus jamaicensis
Authors: Cotter John R.
Published: February 2005

Retinal connections were studied in Eptesicus fuscus and Artibeus jamaicensis using anterograde axonal degeneration and autoradiographic techniques following unilateral enucleations and uniocular injections of radioactive amino acids. Although each retina projected bilaterally to the brainstem, the number of silver grains in the emulsion of autoradiographs indicated that nearly all fibers in the optic nerve entered the contralateral optic tract. Ipsilaterally, a major portin of the projection ended in the suprachiasmatic nucleus; caudal to the suprachiasmatic nucleus, the amount of label was so small that individual silver grains were counted to determine the location and quantity of lebel in other ipsilateral nuclei. In both species the retinal projection terminated bilaterally in the suprachiasmatic, dorsal lateral geniculate, ventral lateral geniculate, and pretectal olivary nuclei and contralaterally in the posterior pretectal nucleus, superficial gray layers of the superior colliculus, and nuclei of the accessory optic system. In Eptesicus the projection to the nucleus of the optic tract ended contralaterally, and in Artibeus it ended in this nucleus bilaterally. The results of this study revealed a basic theme in the optic projection of the two ecologically different microchirop. terans. The results differed, however, in that the projection was larger and visually related nuclei were better developed in Artibeus. Such variations are presumed to relate to eye size and the relative use of vision by the two chiropterans.
Morphology of the bovine epididymis
Authors: Goyal Hari Om
Published: February 2005

The epididymis of the bull was divided into six regions, and morphological differences between regions were studied. The epithelium of all regions contained four cell types: principal and basal epithelial cells, and intraepithelial lymphocytes and macrophages. The epithelium of regions II–V also contained a few apical cells. Principal cells of all regions possessed an endocytotic apparatus including stereocilia underlain by canaliculi, coated vesicles, and subapical vacuoles (up to 1 μm in diameter); however, large vacuoles with a flocculent content and multivesicular bodies (up to 5 μm in diameter) were most numerous in regions II, III, and IV. The unique features of principal cells of region I were the presence of well‐developed Golgi bodies, few lipid droplets, and whorls of smooth endoplasmic reticulum in the supranuclear cytoplasm. Numerous mitochondria, distended cisternae of rough endoplasmic reticulum, and dense granules characterized the infranuclear cytoplasm of the principal cells of regions II–VI; however, these features were more developed in region V. Apical cells were characterized by the apical location of the nucleus, many mitochondria in the apical cytoplasm, and few microvilli at the luminal border. Basal cells with few cytoplasmic lipid droplets were present throughout the length of the epididymis but appeared more numerous in region V. Intraepithelial lymphocytes were present at all levels of the epithelium but were never seen in the lumen. Intraepithelial macrophages containing heterogenous granules, eccentric nuclei, and pseudopods were invariably seen near the basal area of the epithelium in all regions. These observations are discussed in an effort to define the role of each cell type in the epididymal epithelium.
Development of neuroepithelial bodies in intact and cultured lungs of fetal rats
Authors: Carabba Victor Hugo , Sorokin Sergei Pitirimovitch , Hoyt Richard Francis
Published: February 2005

Intact, 14‐ to 21‐day fetal rat lung pairs, neonatal lungs, and cultured 15‐ and 16‐day lung explants were examined in 2‐μm‐thick glycol methacrylate sections stained by PAS‐lead hematoxylin. Selected stages were also studied in histochemical preparations for aliesterase and formaldehyde‐induced monoamine fluorescence, as well as by scanning and transmission electron microscopy. Neuroepithelial bodies (NEBs) first appear in pseudoglandular lungs at 15 days in vivo as pyramidal groups of basal, diffusely lead‐hematoxylin‐positive cells in glycogen‐depleted epithelium of main and lobar bronchi. By day 16, primitive NEBs occur within three to four generations of the terminal buds, and older, proximal bodies are larger and more distinctive than at 15 days. Aliesterase activity is first detected in basally located, developing NEBs on day 16. During the canalicular and alveolar sac periods, NEBs appear and mature on a proximal‐to‐distal gradient along the airway, as they do in developing rabbit and human lungs. As earlier‐formed airways elongate, additional NEBs appear and supplement the population already present. By days 20–21, NEBs occur at all airway levels down to the bronchiolo‐alveolar junctions, and many of the cells have discrete PAS‐ and lead‐hematoxylin‐positive, infranuclear granules. Near term some NEBs exhibit serotonin fluorescence after incubation in 5‐hydroxytryptophan and have abundant, ca. 100‐nm, electron‐dense granules. These are concentrated toward the cell base like the stained granules visualized by light microscopy. Similar results were obtained from lungs placed in organ culture. From 2 days in culture to a time equivalent to term, NEB formation parallels that in vivo, indicating that developmental requirements are met in in vitro. Taken altogether, morphologic and cytochemical evidence suggests that NEBs of rats are functional in late fetal life and that their development is relatively independent of extrapulmonary influences and of the intraepithelial ingrowth of sensory nerve endings.
Distribution of dipeptidyl peptidase II (Dpp II) in rat spinal cord
Authors: Gorenstein Charles , Swett John E.
Published: February 2005

The histochemical localization of dipeptidyl peptidase II (Dpp II; E.C. 3.4.14.2) activity was demonstrated at the light microscope level in the rat spinal cord. Prominent staining was observed in motoneurons of the ventral horn and in medium to large neurons in the deep laminae of the dorsal horn, the intermediate gray, and in lamina X surrounding the spinal canal. Within neurons, Dpp II was localized largely in cell perikarya and large primary dendrites with no staining observed in cell nuclei. Neurons in the superficial dorsal horn lack Dpp II enzyme activity. Nonneuronal elements which also stained prominently were pericytes associated with blood vessels and ependymal cells lining the lumen of the spinal canal. A few oligodendrocytes and astrocytes were also stained, but they represented a minor component of the total amount of Dpp II activity. Following ventral root injury, Dpp‐II‐containing motoneurons degenerate; some glial cells in the region of degenerating neurons become Dpp II positive. The localized distribution of Dpp II in spinal cord neurons suggests that this proteolytic enzyme may play a role in the metabolism of an unidentified neuropeptide.
Reproductive biology of the female leaf–nosed bat, Macrotus californicus, in southwestern united states: I. A morphometric analysis of the annual ovarian cycle
Authors: Crichton Elizabeth G. , Krutzsch Philip H.
Published: February 2005

In Macrotus californicus (Phyllostomatidae), normal embryogenesis (March–June) is preceded by a period of delayed development (October – March) characterized by implantation and slow growth of the embryo to the primitive streak stage. The events of the annual reproductive cycle can be correlated with ovarian dynamics. Waves of follicular growth appear to be initiated in January and June. Increased multilaminar follicles resulting from the second wave of recruitment appear from August to October. Vesiculation of these follicles is seen in both ovaries from July to January; however, the single Graafian follicle forms only in the right ovary just prior to ovulation in late October‐early November. Left ovarian ovulation can be induced by right ovariectomy. High atresia from July to December may retard embryogenesis by failing to provide an optimal hormone milieu for the conceptus. In addition, luteal cells are small during the initial months of embryonic development. The first wave of follicular growth results in the appearance of an increased percentage of growing follicles in April; resultant enhanced estrogen levels may influence the resumption of normal development, an event which also coincides with luteal cell hypertrophy. It would appear possible, therefore, that delayed development in Macrotus is an expression of luteal cell insufficiency and uterine nutritional incompetence resulting from depressed steroid levels. Termination of delay may be brought about by the action of increased levels of estrogen and/or progesterone on the endometrium, perhaps by influencing the activity of mast cells whose products are known in some species to enhance vascularity which in turn could account for added substances essential to normal fetal growth.
Detection of anionic sites on the cytoplasmic surface of the guinea pig acrosomal membrane
Authors: Enders George C. , Friend Daniel S.
Published: February 2005

The sperm acrosome reaction is an example of exocytosis, accomplished through the fusion of the acrosomal and plasma membranes. As in other examples of exocytosis, the acrosome reaction is initiated by an influx of Ca++, which may promote fusion by binding to anionic sites on adjacent bilayers. In this study we used ruthenium red (RR) and cationic ferritin (CF) to detect anionic sites on the surfaces of acrosomal and plasma membranes of guinea pig spermatozoa. These probes indicate a dense concentration of anionic sites on the cytoplasmic surface of the acrosomal membrane. Higher concentrations of salt (NaCl) were required to inhibit cationic probe labeling of the cytoplasmic surface of the acrosomal membrane compared to the concentration needed to inhibit the plasma membrane binding. The added NaCl also increased the separation of the plasma from the acrosomal membrane. Low‐pH buffers stop cationic probe labeling of both membranes. Sections tangential to the acrosomal membrane revealed that the cation probes bound in a linear pattern, similar to the periodicity and distribution of intramembraneous particles observed in freeze‐fracture replicas. Following fusion of the plasma and acrosomal membrane during the acrosome reaction, we could no longer detect a dense concentration of anionic sites on the cytoplasmic surface of the fused vesicles. The results indicate that the dense concentrations of anionic sites are either masked or lost following fusion with the overlying plasma membrane.
A functional and morphological study of cells adjacent to ectopic bone implants in rats
Authors: Walters Linda M. , Schneider Gary B.
Published: February 2005

Subcutaneous implantation of bone chips into normal and osteopetrotic (ia) rats results in the formation of multinucleate giant cells (MNGCs) adjacent to the bone surface. In this study the resorptive and morphological characteristics of the cells surrounding these implants were assessed to determine if the bone‐resorbing defects seen in ia animals would be mimicked, thus giving validity to the use of this system as a model for the study of osteoclastic lineage and function. Direct measurement of in vivo bone resorption was achieved through the use of 45Ca‐labelled bone‐chip pairs that were primarily osteoid‐exposed and freeze‐thawed (FT), primarily mineral‐exposed and bleached (B), or primarily mineral‐exposed and collagenase‐treated (CT). Comparison of the 45Ca content of implanted chips to that of controls indicated the total 45Ca release during a two‐week implantation period. There was no significant difference in the amount of label released between normal and ia animals. Both normal and ia rats showed 23% greater total 45Ca release from mineral‐ versus osteoid‐exposed matrix. Cellular events occurring on the bony substrate were evaluated by light and electron microscopy. At 3 days, bone chips were surrounded primarily by mononuclear cells. By 14 days, MNGCs were present at the bone surface in both ia and normal animals. In mineral‐exposed implants, 40–50% of the bone surface was covered by MNGCs as compared to 20% of the osteoid‐exposed surface. These MNGCs possessed occasional clear zones, but did not exhibit ruffled borders; therefore, they could not be classified as osteoclasts. Thus, the defects seen in ia mutants were not reproduced in this implant system. The 45Ca release that occurred was probably due to the action of mononuclear phagocytes and macrophage polykaryons rather than to true osteoclastic bone resorption.
Mucosal nerves and smooth muscle relationships with gastric glands of the opossum: An ultrastructural and three‐dimensional reconstruction study
Authors: Seelig L. L. , Schlusselberg D. S. , Smith W. K. , Woodward D. J.
Published: February 2005

The precise anatomical relation by which autonomic nerve endings contact gastric epithelial cells to enhance the rate of gastric secretions is not fully understood. The aim of the present study was to clarify this issue by using the technique of serial section reconstruction of areas of the gastric mucosa. The work also explored the possibility of a functional role for a system of smooth muscle strands in the gastric mucosa that emanate from the muscularis mucosa, run in the lamina propria, and are associated in a unique manner with the gastric glands. Electron microscopic serial sections of the gastric mucosa were performed to visualize the entire limiting membrane of gastric epithelial cells to determine any nerve associations (especially varicose endings) with these cells. Evaluation of serial sections of five separate parietal cells showed that their basal membrane did not come in close contact (nearest distance 500 nm) with any nerve axon or varicosity. Moreover, the axons passing in the area of these cells ultimately showed varicose endings associated with smooth muscle cells in the adjacent connective tissue (often separated by only 20 nm), with mast cells or with vascular elements. Additionally, the lateral membrane of these five parietal cells did not contact any endocrine cell in the epithelium, although other parietal cells in the area were adjacent to endocrine cells. Chief cells in the immediate area also did not form any close associations with nerve varicosities. Random analysis of 5,000 additional epithelial cells in these sections showed no close associations to nerve elements with significant accumulations of neurosecretory vesicles (varicosities). Because of the observed existence of innervation to the smooth muscle strands in the area of the gastric glands, serial 1‐μm epoxy sections of the gastric mucosa were prepared, and profiles of smooth muscle and gastric glands were entered into a computer‐assisted reconstruction system. Three‐dimensional reconstruction techniques were employed to reveal the existence of a unique association between the mucosal smooth muscle strands and the gastric glands. The muscle strands arose from the muscularis mucosa at regular intervals and became branched to form an intricate wrap around a series of gastric glands that empty into one gastric pit. Branching of the muscle strands initially occurred at the point where they approached the base of the glands and then emanated into the connective tissue around the glands in a crossing pattern, ending at the base of the gastric pit. Although muscarinic agents have been shown to directly stimulate parietal cells to secrete acid, these findings have led us to postulate that autonomic nerve stimulation may also aid gastric secretion both by stimulation of mast cells and by glandular excretion mediated via mucosal muscular contractions.
The effects of chlorcyclizine‐induced glycosaminoglycan alterations on palatal mesenchyme‐basal lamina relationships in the mouse
Authors: Brinkley Linda L. , Morris‐Wiman Joyce
Published: February 2005

The relationships of mesenchymal cells to the basal lamina underlying regions of the palatal‐shelf epithelium that are known to increase in cell density during shelf reorientation are quantitatively different from those of cells underlying neighboring regions that do not increase in cell density. Chlorcyclizine‐induced alterations of the extracellular matrix were used to investigate the possible contribution of extracellular matrix to these differences. Chlorcyclizine causes hyaluronate and the chondroitin sulfates to be degraded into pieces with smaller molecular weights and lower charge densities, with little or no effect on their synthesis, and also results in cleft palate. Pregnant CD‐1 mice were gavaged with chlorcylizine on days 10.5, 11.5, and 12.5 of gestation, and the fetuses were harvested on day 13.5. Some palatal shelves were excised immediately and fixed for electron microscopy; other heads were partially dissected and incubated for 4 hr prior to fixation. In normal heads differences in mesenchymal cell configurations are detectable after 4 hr in vitro. Electron micrographs were taken of the epithelial‐mesenchymal interface in nasal and oral regions that increased in epithelial cell density and in nasal and oral regions which did not. Several variables of mesenchymal cell configuration were measured in a 500‐nm‐wide zone delimited on photographic prints. Chlorcyclizine‐induced glycosaminoglycan alterations resulted in quantifiable, region‐specific differences in mesenchymal cell relationships to the basal lamina and in the ultrastructural appearance of the zone immediately subjacent to the basal lamina. These results suggest that the epithelial‐mesenchymal interface and sublaminar zone of the nasal and oral regions as well as their active and inactive segments may be constitutively different.
Passage of microspheres through vessels of normal and split hydronephrotic rat kidneys
Authors: Sossenheimer Michael , Fleming John T. , Steinhausen Michael
Published: February 2005

Microspheres (15 μm) were injected intracardially in rats. By means of in vivo microscopy of the split hydronephrotic kidney microcirculation, the passage of microspheres through renal blood vessels was analyzed. Additionally, three sets of experiments were conducted, one consisting of rats with nonnal kidneys, one of rats 1th hydronephrotic kidneys, and one of rats with hydronephrotic kidneys under vasodilation. In vivo microscopic as well as histological studies show that the passage of 15‐μm microspheres is dependent on the postinjection interval Microspheres are capable of locally dilating preglomerular vessels and moving towards the glomeruli. Therefore, estimates of preglomerular vessel diameters with microsphere experiments ought to be controlled by intravital microscopy.
Development of the vasculature of the pectoral fin in the Australian lungfish, Neoceratodus forsteri
Authors: Saito Hiroaki
Published: February 2005

The development of the vasculature of the pectoral fin in the Australian lungfish, Neoceratodus forsteri, was studied by the dye‐injection method. Only a single primitive subclavian artery appears from the dorsal aorta for the fin anlage, and it passes laterally through the postaxial region of the structure. The venous channel draining into the posterior cardinal vein is located in the preaxial region medially. As development proceeds, the arteriovenous arrangement in the pectoral fin anlage changes as follows: (1) one artery and one venous plexus, (2) two arteries and one vein, (3) three arteries and one vein, (4) four arteries and one vein, (5) three arteries and two veins, and (6) two arteries (radial and ulnar) and three veins (radial, ulnar, and ulnar marginal).

The fin anlage through embryonic first rotation has gradually changed its postaxial margin to face dorsally and its preaxial margin to face ventrally. The second rotation causes the original preaxial margin to become dorsal and the original postaxial margin to become ventral. As a result, the radial and ulnar arteries are observed in the dorsal and ventral regions, respectively, in the medial side of the fin instead of in the lateral side as seen in the previous stage.
Skeletal biology in the toothless (osteopetrotic) rat
Authors: Seifert Mark F. , Popoff Steven N. , Marks Sandy C.
Published: February 2005

The toothless (tl) rat is a nonlethal osteopetrotic mutation characterized by the presence of few osteoclasts and the failure to be cured by bone‐marrow transplantation. We examined the skeletal biology of tl rats and normal littermates up to 6 weeks after birth. Osteoclasts in tl rats were small, reduced 25‐fold in number, and had greatly reduced concentrations of acid hydrolases. Bone shape internally and externally reflected reduced bone resorption, and tl rats were hypophosphatemic and mildly hypocalcemic at 2 weeks. These data indicate that the basic defect in tl rats is one of differentiation of osteoclasts and, coupled with the observation that normal bone‐marrow cells cannot develop into osteoclasts in the tl skeleton, suggest that the defect lies in the skeletal microenvironment.
Normal stages of cardiac organogenesis in the mouse: I. Development of the external shape of the heart
Authors: Vuillemin Mauricette , Pexieder Tomas
Published: February 2005

Normal development of the mouse embryonic heart was studied at the organ level using microdissection and scanning electron microscopy (SEM). Altogether 225 embryos, sampled at 8‐hour intervals between 11ed (ed = embryonic day; day of vaginal plug = led) and 15ed were collected. Their hearts were fixed by high flow‐low pressure perfusion, micro‐dissected, and observed in SEM. Standardized frontal, right profile, and left profile SEM micrographs were obtained and analyzed.

The main purpose of this study was to create a series of normal stages of mouse cardiac development as a reference for ongoing studies in experimental cardiac teratology (e.g., in fetal mouse trisomies). Comparisons with chick, human, and dog embryonic hearts, prepared using the same technique, show that the mouse embryonic heart is characterized by a relatively deep interventricular sulcus. The absence of a conoventricular sulcus in the mouse results in poor definition of the boundary between the conus and the right ventricle. The external separation of the aorta and the pulmonary artery is evident from 13ed onward. The respective positions of the great arteries (aorta dextroposterior, pulmonary artery sinistroanterior) does not change until the end of cardiac organogenesis (15ed in the mouse).
Hemopoiesis in the human yolk sac
Authors: Takashina Toshimitsu
Published: February 2005

The endodermal layer of the human yolk sac was examined three‐dimensionally with light microscopy on serial sections using scanning electron microscopy and transmission electron microscopy to find the origin of hemo poiesis in the yolk sac. Cell‐labelling techniques were also employed using the monoclonal anti‐transferrin receptor antibody. Orifices of the endodermal and intracellular tubules facing the yolk‐sac cavity were demonstrated on the endodermal surface. Various‐sized blood cells in various stages of differentiation and maturation were distributed in the yolk‐sac cavity and tubules and were observed also at the orifices of the tubules. The morphological and the immunological findings suggest that blood cells with large nuclei in the endodermal layer are the most immature. The present results suggest that blood cells originate from the endodermal layer and are carried to the embryo through the yolk sac cavity and the vitel‐line duct. It is probable that the endodermal and intracellular systems of tubules have an important role in the transport of blood cells, including stem cells.
Bidirectional closure of the rostral neuropore in the human embryo
Authors: O'Rahilly Ronan , Müller Fabiola
Published: February 2005

The length of each neuropore was measured in 23 human embryos of stages 10–12 (about 22–26 days), and the closure of the lips of the rostral neuropore was studied in 24 embryos of stage 11 (about 24 days), with particular reference to the terminal lip. Graphic reconstructions were prepared from two particularly suitable examples, and mitotic figures were plotted for one of these. The lengths of the rostral and caudal neuropores are basically similar, but the rostral opening closes 1 day earlier and more abruptly (within a few hours) than the caudal (which takes a day). Closure of the rostral neuropore in the human embryo is bidirectional, proceeding simultaneously from (1) midbrain and diencephalon 2 and (2) the telencephalic region adjacent to the chiasmatic plate. Species differences are emphasized. Closure at the terminal lip of the neuropore is by fusion of right and left neural folds, as occurs elsewhere during primary neurulation. The rostral end of the neural plate in the median plane is, in the human embryo, at the rostral limit of the chiasmatic plate. Histological differences, however, exist between closure at the terminal lip and that at the dorsal lip: the surface epithelium plays a more significant role at the terminal lip, and the seam is more visible and presumably stronger. In future anencephaly it has been found that fusion at the terminal lip may occur, although that at the dorsal lip is deficient.
Accessory cells in the gill epithelium of the freshwater rainbow trout Salmo gairdneri
Authors: Pisam M. , Prunet P. , Rambourg A.
Published: February 2005

Two types of mitochondria‐rich cells were identified in the gill epithelium of the freshwater‐adapted rainbow trout, Salmo gairdneri, after selective impregnation of their tubular system with reduced osmium. A first type consisted of large cells with a poorly developed and loosely anastomosed tubular system; thus, that resembled the chloride cells commonly encountered in the gill epithelium of freshwater‐adapted euryhaline fishes. A second type comprised smaller cells with an extensively developed and tightly anastomosed tubular system. These never reached the basal lamina of the gill epithelium and were adjacent to chloride cells, to which they were linked by shallow apical junctions (100‐200 nm); thus, they resembled accessory cells, which are currently found in the gill epithelium of sea‐water‐adapted fishes but are usually lacking in freshwater living fishes. Transfer of the freshwater‐adapted trout into seawater induced the proliferation of the tubular system in the chloride cells and the formation of lateral plasma membrane interdigitations between accessory cells and the apical portion of the chloride cells. The length of the apical junction sealing off this ex tended intercellular space was reduced to 20‐50 nm. The tubular system of the accessory cells was not modified. The extension of the tubular system in the chloride cells of the seawater‐adapted fishes indicated that, as in most euryhaline fishes, these cells have a role in the adaptation of the rainbow trout to seawater. In contrast, the function of the presumptive accessory cells in fresh water trout remains to be established.
Colonization of the developing pancreas by neural precursors from the bowel
Authors: Kirchgessner A. L. , Adlersberg M. A. , Gershon M. D.
Published: February 2005

Neurons in ganglia of the myenteric plexus of the duodenum and stomach have recently been demonstrated to innervate pancreatic ganglia and transsynaptically to excite acinar and islet cells. The hypothesis that crestderived cells first colonize the foregut and secondarily enter the pancreas by way of the pancreatic buds was tested. Studies were done with fetal rats (days E11–E15). Pancreatic rudiments and foregut were explanted separately and in co‐culture. The development of neurons in the explants, identified by demonstrating the immunoreactivities of neurofilaments and growthassociated protein‐43 (GAP‐43), provided an indirect assay for the presence of neural precursors in the tissue at the time of explantation. Cells of putative neural crest origin were visualized immunocytochemically using the monoclonal antibody, NC‐1. Additional markers included the immunoreactivities of dopamine‐β‐hydroxylase (DBH), which is expressed by vagal crest‐derived cells that colonize the bowel, neuropeptides (substance P and neuropeptide Y [NPY]) found in mature pancreatic neurons, and serotonin (5‐HT), which is located in the cell bodies of enteric but not pancreatic neurons. Neurons were detected in cultures of foregut, but not pancreas, when these tissues were explanted by themselves at days E11 and E12. At E11 neural precursors did not leave explants of bowel or migrate into co‐cultured pancreatic rudiments. When the foregut was explanted at E12, however, neural precursors migrated away from the bowel, giving rise both to distant ganglia and to neurons within co‐cultured pancreatic rudiments. Intrapancreatic ganglia developed in the co‐cultures even when the pancreatic attachment to the bowel was severed. Neurons appeared in pancreatic rudiments explanted by themselves on day E13. Neurons developing in pancreatic explants expressed the immunoreactivities of DBH, substance P, and NPY, but not 5‐HT. These observations support the idea that pancreatic ganglia develop from crest‐derived cells that first colonize the fetal rat foregut and there acquire the ability to colonize the pancreas. A later migration into the pancreatic rudiments of a subset of the original émigrés or their progeny between days E12 and E13 gives rise to a network of pancreatic ganglia that can be regarded as an extension of the enteric nervous system. © 1992 Wiley‐Liss, Inc.
EMA: A developmentally regulated cell‐surface glycoprotein of CNS neurons that is concentrated at the leading edge of growth cones
Authors: Baumrind Nikki L. , Parkinson David , Wayne Denise B. , Heuser John E. , Pearlman Alan L.
Published: February 2005

To identify cell‐surface molecules that mediate interactions between neurons and their environment during neural development, we used monoclonal antibody techniques to define a developmentally regulated antigen in the central nervous system of the mouse. The antibody we produced (2A1) immunolabels cells throughout the central nervous system; we analyzed its distribution in the developing cerebral cortex, where it is expressed on cells very soon after they complete mitosis and leave the periventricular proliferative zone. Expression continues into adult life. The antibody also labels the epithelium of the choroid plexus and the renal proximal tubules, but does not label neurons of the peripheral nervous system in the dorsal root ganglia. In dissociated cell culture of embryonic cerebral cortex, 2A1 labels the surface of neurons but not glia. Immunolabeling of neurons in tissue culture is particularly prominent on the edge of growth cones, including filopodia and the leading edge of lamellipodia, when observed with either immunofluorescence or freeze‐etch immunoelectron microscopy. Immunopurification with 2A1 of a CHAPS‐extracted membrane preparation from brains of neonatal mice produces a broad (32–36 kD) electrophoretic band and a less prominent 70 kD band that are sensitive to N‐glycosidase but not endoglycosidase H. Thus the 2A1 antibody recognizes a developmentally regulated, neuronal cell surface glycoprotein (or glycoproteins) with complex N‐linked oligosaccharide side chains. We have termed the glycoprotein antigen EMA because of its prominence on the edge membrane of growth cones. EMA is similar to the M6 antigen (Lagenaur et al: J. Neurobiol. 23:71–88, 1992) in apparent molecular weight, distribution in tissue sections, and immunoreactivity on Western blots, suggesting that the two antigens are similar or identical. Expression of EMA is a very early manifestation of neuronal differentiation; its distribution on growth cones suggests a role in mediating the interactions between growth cones and the external cues that guide them. © 1992 Wiley‐Liss, Inc.
Expression of Hox 2.1 protein in restricted populations of neural crest cells and pharyngeal ectoderm
Authors: Kuratani Shigeru C. , Wall Nancy A.
Published: February 2005

A polyclonal antibody, αHox 2.1a, was used to localize Hox 2.1 protein in presumptive neural crest cells and nodose ganglion of 8.5–10.0 day p.c. mouse embryos. The following results were obtained: (1) The nodose placode, in its epithelial state, first expresses Hox 2.1 protein at 9.0 d.p.c. By 9.5 d.p.c. presumptive migrating neuroblasts between the nodose placode and ganglion primordium also express Hox 2.1 protein. (2) At 9.5 d.p.c., presumptive crest cells lateral to the cephalic cardinal vein and within pharyngeal arches 4 and 6 are immunoreactive for αHox 2.1a. In the arch 6 region, positive cells extend medially to a mesenchymal cell population on the lateral aspect of the foregut wall. (3) At 10.0 d.p.c., Hox 2.1 protein expression in putative crest cells is restricted to the arch 6 cell population. A similar staining pattern is seen using αHox 2.1a with chick embryos. Comparison with the chicken embryo suggests that the Hox 2.1 positive cells in the pharyngeal arch and those on the lateral aspect of the foregut in the mouse embryo correspond to the caudalmost subpopulation of the circumpharyngeal crest (Kuratani and Kirby: Dev. Dyn. 191:215–227, 1991; Anat. Rec. 234:263–280, 1992). These results are consistent with a role for Hox 2.1 in pattern formation in the caudalmost region of the vertebrate head. © 1992 Wiley‐Liss, Inc.
The zonal expression of α‐fetoprotein transgenes in the livers of adult mice
Authors: Emerson Julia Andrew , Vacher Jean , Cirillo Lisa Ann , Tilghman Shirley M. , Tyner Angela L.
Published: February 2005

The developmental regulation of the α‐fetoprotein (AFP) gene in liver results in high‐level expression in the fetus, followed by dramatic transcriptional repression after birth. We have examined the mouse AFP gene for transcriptional control sequences that may be involved in its postnatal repression in liver. We showed previously that removal of a DNA region between positions −250 base pairs (bp) and −838 bp of the AFP gene resulted in the persistence of expression of an AFP minigene in the postpartum liver of transgenic mice (Vacher and Tilghman, Science 250:1732–1735, 1990). This study examines the distribution of these transgene transcripts in liver using in situ hybridization. We show that there is a zonal distribution of minigene transcripts in the adult livers of these animals. Hepatocytes surrounding the central veins express high levels of minigene transcripts, while hepatocytes in the intermediate and portal areas contain few, if any, transcripts. Quantitative RNAse protection analysis shows a decrease in transgene RNA levels after birth, consistent with repression in all but a small subset of hepatocytes. These results indicate that repression in the pericentral hepatocytes is dependent upon the presence of a cis‐acting, negative‐regulatory domain, which is located between the enhancers and the proximal promoter of the AFP gene. In contrast, this domain is not essential for complete repression of AFP transgenes in the intermediate zone and periportal hepatocytes. © 1992 Wiley‐Liss, Inc.
Coordinate expression of IGF‐I and its receptor during limb outgrowth
Authors: Geduspan J. S. , Padanilam B. J. , Solursh M.
Published: February 2005

The morphogenetic mechanisms involved in shaping the embryo are largely unknown. Previous studies from this laboratory suggest that the mesonephros promotes limb outgrowth in ovo in the chicken embryo and might be involved in early limb morphogenesis, since damage to the mesonephros results in truncated limbs. In limb bud organ cultures, the presence of the mesonephros promotes cartilage formation. This effect can be reproduced by exogenous IGF‐I or prevented by blocking antibody to IGF‐I. In order to examine the hypothesis that mesonephros‐derived IGF‐I is involved in the early morphogenesis of the limb, we examined the spatial and temporal expression of IGF‐I and type I receptor for IGF by in situ hybridization at stages when the onset of limb development occurs. The results show that neither transcript is detected at stage 13, prior to the appearance of the limb bud; but both transcripts are detected in the mesonephros at stage 14, an early stage in limb outgrowth. The hybridization signal in the mesonephros for both transcripts increases with development and signal was codistributed as well. At stage 18 the level of receptor transcripts detected in the flank relative to the limb decreased. Thus, the temporal and spatial patterns of expression of IGF‐I and its receptor are consistent with their involvement in the initiation of limb outgrowth and support the model that localized expression of a growth factor and its receptor can be involved in shaping the embryo. © 1992 Wiley‐Liss, Inc.
Localization of pro‐α2(V) collagen transcripts in the tissues of the developing mouse embryo
Authors: Andrikopoulos Konstantinos , Suzuki Hiroaki R. , Solursh Michael , Ramirez Francesco
Published: February 2005

Correct assembly of fibrillar collagen networks plays a critical role in animal morphogenesis. Very little is known about the contribution of the so‐called minor fibrillar collagens (types V and XI) to fibrillogenesis. Here we examined the developmental expression of the mouse pro‐α2(V) collagen gene (col5a2) after the cloning and sequencing of cDNAs that cover the entire length of the message. Transcripts of col5a2, detectable as early as 9 days of gestation, localize with distinct patterns in the tissues of day 12.5 and day 16.5 fetuses. The earlier developmental stage is characterized by low and diffuse col5a2 expression in the peritoneal membranes and intestinal and craniofacial mesenchymes. The later stage exhibits higher and more restricted col5a2 mRNA accumulation in primary ossified regions, perichondrium, joints, tendon, atrioventricular valve of the heart, and selected portions of the head. A parallel analysis using a cartilage‐specific pro‐α1(II) collagen (col2a1) probe confirmed that these two collagen genes are transcribed in a mutually exclusive manner during mouse embryogenesis. On the other hand, the developmental pattern of col5a2 expression closely resembles that of the type I collagen, thus further substantiating the notion that these macromolecules cooperate in the formation of fibrillar networks in non‐cartilaginous matrices. © 1992 Wiley‐Liss, Inc.
Localization of epidermal growth factor and its receptor in mandibular molars of the rat prior to and during prefunctional tooth eruption
Authors: Wise Gary E. , Lin Fan , Fan Wei
Published: February 2005

Immunoperoxidase localization of epidermal growth factor receptors (EGFR) and epidermal growth factor (EGF) itself was examined in rat first and second mandibular molars postnatally from day 0 to 12. The results showed that the dental follicle stained heavily for EGFR from day 0 to 8, declined in staining at day 9, and was devoid of stain from day 10 onward. Preosteoblasts and osteoblasts of alveolar bone also stained and lesser staining of ameloblasts and odontoblasts was observed. Except for staining of occasional isolated cells, the stellate reticulum did not stain. Light staining of the dental pulp of the first mandibular molar was seen from day 0 onward but the pulp of the second molar did not stain until approximately day 6. With respect to EGF, the dental follicle also stained for it until day 12. The ameloblasts stained more intensely for EGF than for EGFR. Because injections of EGF cause premature eruption of teeth and because the presence of a dental follicle is necessary for eruption, this study suggests that EGF could have its effect on the follicle as seen by the presence of EGFR receptors on the follicle. Moreover, because EGF exerts its effects early (day 0–3) to cause eruption and because the influx of monocytes into the follicle to form osteoclasts for bone resorption for eruption occurs early, the heavy staining for EGFR in the follicle early followed by the absence of staining at day 10 correlates chronologically with the key molecular and cellular events of eruption. Finally, the presence of EGF in the follicle, as well as enamel organ, could provide an endogenous source of EGF to regulate tooth eruption, either by an autocrine or a paracrine effect. Thus, the localization of EGFR and EGF in the dental follicle coupled with the chronology of localization suggests that EGF could play a physiological role in tooth eruption. © 1992 Wiley‐Liss, Inc.
Comparison of Hensen's node and retinoic acid in secondary axis induction in the early chick embryo
Authors: Chen Yiping , Solursh Michael
Published: February 2005

Retinoic acid (RA) and Hensen's node, the organizer center in the chick embryo, have been shown to have polarizing activity when applied or grafted into the chick limb bud. Here we investigate and compare the effects of RA and grafted Hensen's node on the early chick embryo. Anion exchange beads soaked with RA at concentrations ranging from 5 to 100 ng/ml and implanted on the anterior side or on the left side of the host anteroposterior axis of a stage 4 chick embryo in ovo have the ability to induce secondary axis formation, while beads soaked with RA of the same concentration and implanted on the right side or on the posterior side of the host axis are unable to induce the secondary axis. All of the induced axes contain trunk‐tail structures. Hensen's node from quail embryos implanted into the early chick blastoderm could also cause the formation of secondary axes in addition to self‐differentiation of the graft into a secondary axis. Both RA and grafted Hensen's node caused the inhibition of forebrain development with an increase in hindbrain development and the host heart to loop in an abnormal direction. The results support the hypothesis that Hensen's node is a source of RA which is involved in early embryo‐genesis. Alternatively, RA might stimulate the formation of Hensen's nodal properties in adjacent tissue. © 1992 Wiley‐Liss, Inc.
Cell interaction and its role in mesoderm cell migration during Xenopus gastrulation
Authors: Winklbauer Rudolf , Selchow Andreas , Nagel Martina , Angres Brigitte
Published: February 2005

In the Xenopus gastrula, the mesoderm moves as a coherent cell aggregate across the blastocoel roof toward the animal pole. We show that the cohesion of the mesoderm is not only mechanically necessary, but that aggregate formation has profound effects on the migratory behavior of mesoderm cells. Whereas isolated mesoderm cells are bi‐ or multipolar, move stepwise and change their direction of movement frequently, aggregated mesoderm cells migrating on their in vivo substrate appear unipolar and move continuously and persistently. Moreover, only mesoderm cell aggregates, but not single cells, can follow guidance cues present in the extracellular matrix of the blastocoel roof substrate. Thus, the cohesion of the mesodermal cell mass is an essential feature of mesoderm migration during Xenopus gastrulation. We show that the Ca2+‐dependent cell adhesion molecule U‐cadherin is involved in mediating this cohesion. © 1993 Wiley‐Liss, Inc.