bluuebunny/crossref_metadata_2025 huggingface dataset:
Embryonic expression of tenascin‐X suggests a role in limb, muscle, and heart development
Authors: Burch Grant H. , Bedolli Melanie A. , McDonough Stephen , Rosenthal Stephen M. , Bristow James
Published: February 2005

Tenascin‐X (TN‐X) is the newest member of the tenascin family of extracellular matrix proteins and it is highly expressed in muscular tissues during development. To gain insight into the possible functions of TN‐X during development, we evaluated its expression in the rat embryo. Using an 800 bp cDNA encoding the fibrinogen‐like domain of TN‐X, we show that TN‐X expression begins in migrating cells of the epicardium in the E12 heart. The epicardium provides progenitors of fibrous and vascular tissue to the developing heart. After the epicardium is complete, TN‐X is expressed in the sub‐epicardial space in association with developing blood vessels, and later by non‐myocytes dispersed through the myocardial wall. A similar pattern of TN‐X expression, first in connective tissue surrounding muscle, and then by a subset of cells within muscle, was seen in para‐axial, body wall, craniofacial, and appendicular muscle. This pattern suggests a role in connective tissue cell migration and late muscle morphogenesis. TN‐X is also highly expressed in the interdigital space at E15 and surrounding developing tendons, suggesting an additional role in cell fate determination. Although the pattern of TN‐X expression is distinct from that of tenascin C, they are frequently expressed in close proximity. Indirect genetic evidence in humans suggests an essential function for TN‐X, and the pattern of TN‐X expression in heart, skeletal muscle, and limb is consistent with this hypothesis. ©1995 Wiley‐Liss, Inc.
Specification of multiple vertebral identities by ectopically expressed Hoxb‐8
Authors: Charité Jeroen , de Graaff Wim , Deschamps Jacqueline
Published: February 2005

We have recently generated Hoxb‐8 gain‐of‐function mutant embryos, using a Hoxb‐8 transgene driven by a retinoic acid receptor β2 promoter to extend the expression domain to more anterior regions of the embryo (Charité et al. [1994] Cell 78:589–601). Here we describe the phenotype in the axial skeleton of transgenic embryos. The severity of the phenotype was variable, and cervical vertebrae and the base of the skull were affected in different ways. We observed fusion of the anterior arch of the atlas to the dens of the axis, partial splitting of the vertebral body and the neural arch of the axis, and abnormal morphology of the basioccipital and exoccipital bones. The basioccipital bone projected into the atlas, sometimes fusing to the dens of the axis; the exoccipital bones appeared to be transformed towards neural arch‐like structures. A novel pattern of posterior homeotic transformations was observed, involving cervical vertebrae C3 to C7: the ventral aspect of vertebrae C5 to C7 could acquire different morphologies characteristic of more posterior vertebrae: C5 could be transformed into C6, C7, or T1, C6 into C7 or T1, and C7 into T1. Phenotypes of different severity could be arranged into a phenotypic series, starting with the transformation of C7 to T1 and involving transformation of increasingly more anterior vertebrae into increasingly more posterior identities; no vertebra acquired a more posterior morphology than that of the vertebra immediately caudal to it. Ribs appeared to be formed relatively independently of rib heads; cervical ribs (but not rib heads) could be observed as anterior as C3. The results suggest that higher levels of ectopically expressed Hoxb‐8 result in specification of more posterior vertebral identities. © 1995 wiley‐Liss, Inc.
Developmental defects of the ventromedial hypothalamic nucleus and pituitary gonadotroph in the Ftz‐F1 disrupted mice
Authors: Shinoda Koh , Lei Hong , Yoshii Hironori , Nomura Masatoshi , Nagano Mamoru , Shiba Hiroharu , Sasaki Hiroshi , Osawa Yoshio , Ninomiya Yasuharu , Niwa Ohtsura , Morohashi Ken‐Ichirou , Li En
Published: February 2005

Ad4BP (or SF‐1) has been identified as a transcription factor which regulates all the steroidogenic P450 genes in the peripheral organs, and is encoded by the mammalian homologue of Drosophila FTZ‐F1 gene. mRNA coding for Ad4BP was detected in the hypothalamus and pituitary of rats by RT‐PCR. Immunohistochemical analyses using an antiserum to Ad4BP in the brain and pituitary revealed that the transcription factor is expressed in nuclei of the dorso‐medial part of the ventromedial hypothalamus (dmVMH) and in some subpopulation of the adenohypophysial cells. Double immunostaining of the pituitary for Ad4BP and trophic peptide hormones, FSH, TSH, and ACTH, indicated a restricted localization of Ad4BP to the gonadotroph. Disruption of the mouse Ftz‐F1 gene was clarified to induce severe defects in the organization of the dmVMH and the function of the pituitary gonadotroph. However, some of the dm VMH neurons and pituitary gonadotrophs persisted, which provided a sharp contrast to complete agenesis of the peripheral steroidogenic tissues (adrenal and gonads) in the mutant mouse. Additional abnormalities were seen in the ventrolateral part of VMH and dorsomedial hypothalamic nucleus, both of which do not express Ad4BP but have strong reciprocal fiber‐connections with the dmVMH. Aromatase P450‐containing cells in the medial preoptico‐amygdaloid region, which were devoid of Ad4BP, persisted even in the brain of the gene disrupted mice. The present results clearly showed that the hypothalamic and pituitary Ad4BPs are essential to normal development of the functional VMH and gonadotroph through some mechanism distinct from that in the peripheral steroidogenic tissues. © 1995 wiley‐Liss, Inc.
Two closely related receptor‐type tyrosine phosphatases are differentially expressed during rat lung development
Authors: Katsura Hideki , Williams Mary C. , Brody Jerome S. , Yu Qiang
Published: February 2005

Transmembrane protein tyrosine phosphatases (PTPases) comprise a newly identified class of receptor‐like molecules. In most cases their ligands and the substrates they dephosphorylate are not known. In order to begin to explore the functions of the PTPases in cell physiology and in mammalian development, we examined the expression patterns of two closely related receptor‐type tyrosine phosphatase genes, namely LAR and PTPδ, in fetal rat lung and in selected adult rat tissues. In the lung, in situ hybridization and immunohistochemistry show that the LAR mRNA and protein are expressed exclusively in the epithelium. In the early embryonic or fetal lung (day 13 to 18) LAR is expressed by all of the epithelial cells of the forming bronchial tree. This widespread pattern of expression is lost later in fetal life (day 21) as the lung matures and acquires the morphologic and biochemical features of the adult organ. LAR gene expression is then confined to two epithelial progenitor cells of the distal airways, namely the bronchiolar Clara cell and the alveolar type II cell. The LAR gene products were also found abundantly expressed in epithelial progenitor cells of adult esophagus, skin, and small intestine, all of which are continuously renewing epithelia. The rat PTPδ gene, on the other hand, is specifically expressed in the mesenchyme of the developing lung. The level of the PTPδ mRNA decreases as the lung matures. These results suggest that the two closely related receptor‐type tyrosine phosphatases are differentially expressed in a tissue‐specific fashion. They are expressed mostly in proliferating cells or in cells which have potential to proliferate. Therefore, one function of the two receptor‐like tyrosine phosphatases may be to regulate proliferation and/or differentiation of different types of cells during development, during normal cell turnover, and during adult tissue repair. © 1995 wiley‐Liss, Inc.
Myoepithelial cell diffeentiation in the developing mammary gland: Progressive acquisition of smooth muscle phenotype
Authors: Deugnier Marie‐Ange , Moiseyeva Elena P. , Thiery Jean Paul , Glukhova Marina
Published: February 2005

The most important portion of the mammary gland development occurs postnatally, with distinct periods of intensive morphogenesis taking place btween birth and puberty and during pregnancy and lactation. To characterize the differentiation process of mammary myopithlial cells, we have studied the expression patterns of several smooth musle phenotypic markers, including contractile proteins, α‐smooth muscle‐actin (α‐SM‐actin), smooth muscle myosin heavy chains (SM‐MHC), and calponin; components of cell‐extracellular matrix aderens junctions, phosphoglucomutase‐related protein (PGM), vinculin variants, integrin subunits; and laminin variant chains in the developing rat mammary gland using immunofluorescence microscopy. α‐SM‐actin‐ and SM‐MHC‐positive cells were found first in newborn animals, while calponin, PGM, and α1 integrin subunit began to be expressd in prepubertal animals (1.5 weeks). Vinculin, β1 and α3 integrin subunit were largely confined to the basal cell layer at all developmental stages examined with greater staining starting at 1.5 weeks. Meta‐vinculin was identifed only in myoepithelial cells of the lactating gland. γ1 laminin chain was present in the mammary gland basement membrane throughout development, while the β2 chain was revealed in 3‐week‐old animals and accumulated later in pospubertal animals (7 weeks). Similarly, β2 laminin chain was absent from the forming alveoli basement membrane in pregnant rats and started to accumulate in the lactating gland. In addition to temporal changes, we have observed spatial differences in the distribution of the phenotypic markers. Both in pre‐ and in postpubertal animals, α‐SM‐actinand SM‐MHC‐positive cells of the growing ductal ends contained low amounts if any of calponin, PGM, and β2 laminin chain. We conclude that during postnatal development, mammary myoepithelial cells progressively acquire a differentiated phenotype as revealed by the expression of various smooth muscle markers. Maturation of the myoepithelial cells is accompanied by upregulation of the smooth muscle integrin expression followed by accumulation of β2‐containing laminin variant. Thus, changes in adhesion system parallel with the myoepithelial cell differentiation. © 1995 wiley‐Liss, Inc.
Dystroglycan mRNA expression during normal and mdx mouse embryogenesis: A comparison with utrophin and the apo‐dystrophins
Authors: Schofield Julian N. , Górecki Dariusz C. , Blake Derek J. , Davies Kay , Edwards Yvonne H.
Published: February 2005

α dystroglycan (156 kDa DAG) and β dystroglycan (43 kDa DAG) are encoded by the same gene and are components of the dystrophin‐associated membrane glycoprotein complex. The dystroglycans together with dystrophin form a link between the extracellular matrix and the intracellular cytoskeleton of the muscle fibre. Using in situ hybridisation to mRNA in embryo sections we have examined the expression of the mouse dystroglycan gene. Dystroglycan transcripts are ubiquitously expressed throughout developmnet but are most abundant in cardiac, skeletal and smooth muscle and in ependymal cells lining the developing neural tube and brain. The expression patterns of dystroglycan and dystrophin ovrlap in the major muscle systems during development, suggesting that the dystrophin‐dystroglycan complex plays an important role during myogenesis. In contrast, the major sites of utrophin expression do not co‐localize with those of dystroglycan suggesting that utrophin may interact with a distinct membrane‐associated complex in these non‐muscle sites. In mdx embryos the pattern of distribution of dystroglycan mRNA remains unchanged, as do those of utrophin and apo‐dystrophin mRNAs. This observation implies that the observed changes in the relative abundance of DAGs and utrophin in dystrophin‐deficient muscle occur post‐transcriptionally. © 1995 wiley‐Liss, Inc.
Appearance of neurons in the developing chick gut
Authors: Fairman Colin L. , Clagett‐Dame Margaret , Lennon Vanda A. , Epstein Miles L.
Published: February 2005

The enteric nervous system is formed from neural crest‐derived cells. These cells enter the gut, migrate, proliferate, and ultimately differentiate into neurons and glia. We have used a human anti‐neuronal autoantibody (ANNA‐1), which recognizes neuron‐specific RNA‐binding proteins of the Hu family as an early marker of neuronal phenotype, to study the appearance of enteric neurons in the developing chicken gut. Immunoreactive cells appear first in the gizzard primordium at E3.5 and are found at progressively more caudal locations in the gut as development proceeds. Nascent neurons are present at the yolk stalk at E4.5, at the ileocecal junction at E6.5, and within the rectum at E7.5–8.5. Neurons appear slightly later in the esophagus. Aggregates of cells resembling developing ganglia were first observed at E6.5 in the distal esophagus and at E8.5 in the proximal esophagus. A small number of cells appeared in the vagus nerve trunks at E4.5 and that number increased at E7.5–8.5. Immunoreactive cells were also found in the sympatho‐aortic plexus between the mesonephri and in the dorsal mesentery. These cells appeared to coalesce and form the ganglionated Nerve of Remak which contained positive cells at E3.5. This Nerve extended to the yolk stalk at E4.5 and to duodendum at E6.5. We conclude that the appearance of nascent neurons occurs first in the gizzard and proceeds more rapidly in a distal than proximal direction along the gut. Furthermore, cells that appear to be nascent neurons are found in the vagus and in the dorsal mesentery. © 1995 wiley‐Liss, Inc.
Coordinate expression of vascular endothelial growth factor receptor‐1 (fit‐1) and its ligand suggests a paracrine regulation of murine vascular development
Authors: Breier Georg , Clauss Matthias , Risau Werner
Published: February 2005

Vascular endothelial growth factor (VEGF) is a candidate regulator of blood vessel growth during embryonic development and in tumors. To evaluate the role of VEGF receptor‐1/flt‐1 (VEGFR1/flt‐1) in the development of the vascular system, we have characterized the murine homolog of the human flt‐1 gene and have analyzed its expression pattern during mouse embryogenesis. Receptor binding studies using transfected COS cells revealed that the murine flt‐1 gene encodes a high affinity receptor for VEGF. The apparent Kd for VEGF binding, as determined by Scatchard analysis, was 114 pM, demonstrating that VEGFR1/flt‐1 has a higher affinity to VEGF than VEGF receptor‐2/flk‐1 (VEGFR2/flk‐1). By in situ hybridization, VEGFR1/flt‐1 was detected in the yolk sac mesoderm already at the early stages of vascular development, while the receptor ligand was expressed in the entire endoderm of 7.5‐day mouse embryos. A comparison with VEGFR2/flk‐1 showed that the two receptors shared a common expression domain in the yolk sac mesoderm, but were expressed at different sites in the ectoplacental cone. The differential expression of the two VEGF receptors persisted in the developing placenta, where VEGFR1/flt‐1 mRNA was detected in the spongiotrophoblast layer, whereas VEGFR2/flk‐1 transcripts were present in the labyrinthine layer which is the site of VEGF expression. In the embryo proper, VEGFR1/flt‐1 mRNA was specifically localized in blood vessels and capillaries of the developing organs, closely resembling the pattern of VEGFR2/flk‐1 transcript distribution. In the developing brain, the expression of VEGF receptors in the perineural capillary plexus and in capillary sprouts which have invaded the neuroectoderm correlated with endothelial cell proliferation and brain angiogenesis. The data are consistent with the hypothesis that VEGF and its receptors have an important function both in the differentiation of the endothelial lineage and in the neovascularization of developing organs, and act in a paracrine fashion. © 1995 wiley‐Liss, Inc.
Enhanced expression of mouse c‐ski accompanies terminal skeletal muscle differentiation in vivo and in vitro
Authors: Namciu Stephanie , Lyons Gary E. , Micales Bruce K. , Heyman Hong‐Chen , Colmenares Clemencia , Stavnezer Ed
Published: February 2005

Overexpression of either v‐ski, or the proto‐oncogene, c‐ski, in quail embryo fibroblasts induces the expression of myoD and myogenin, converting the cells to myoblasts capable of differentiating into skeletal myotubes. In transgenic mice, overexpression of ski also influences muscle development, but in this case it effects fully formed muscle, causing hypertrophy of fast skeletal muscle fibers. In attempts to determine whether endogenous mouse c‐ski plays a role in either early muscle cell determination or late muscle cell differentiation, we analyzed mRNA expression during muscle development in mouse embryos and during in vitro terminal differentiation of skeletal myoblasts. To generate probes for these studies we cloned coding and 3′ non‐coding regions of mouse c‐ski. In situ hybridization revealed low c‐ski expression in somites, and only detected elevated levels of mRNA in skeletal muscle beginning at about 12.5 days of gestation. Northern analysis revealed a two‐fold increase in c‐ski mRNA during terminal differentiation of skeletal muscle cell lines in vitro. Our results suggest that c‐ski plays a role in terminal differentiation of skeletal muscle cells not in the determination of cells to the myogenic lineage. © 1995 wiley‐Liss, Inc.
Expression of M‐twist during postimplantation development of the mouse
Authors: Füchtbauer Ernst‐martin
Published: February 2005

The murine homologue of the Drosophila twist gene has been shown to be essential for head mesenchyme formation and to act as an inhibitor of muscle differentiation. This paper presents a detailed analysis of M‐twist expression patterns from day 7 post coitum (p.c.) to day 18 p.c., indicating a more general function of the M‐twist gene. At day 7 p.c., M‐twist is expressed in the mesoderm outside the primitive streak. Later M‐twist message is predominantly found in the somites, the head mesenchyme, the branchial arches, the limbs, and in the mesenchyme underneath the epidermis. Beginning at day 8 p.c., M‐twist is mainly expressed in undifferentiated cells committed to muscle and cartilage development: this exspression is consistent with a suggested role of M‐twist in inhibiting overt muscle and cartilage differentiation. However, during organogenesis, M‐twistt is expressed in several areas of mesenchyme‐epithelia interactions, suggesting additional tissue specific functions. © 1995 wiley‐Liss, Inc.
Developmental regulation of connexin 40 gene expression in mouse heart correlates with the differentiation of the conduction system
Authors: Delorme Bruno , Dahl Edgar , Jarry‐guichard Thérèse , Marics Irène , Briand Jean‐Paul , Willecke Klaus , Gros Daniel , Théveniau‐Ruissy Magali
Published: February 2005

In adult mouse heart, CX40 is expressed in the atria and the proximal part of the ventricular conduction system (the His bundle and the upper parts of the bundle branches). This cardiac tissue is specialized in the conduction of the electrical impulse. CX40 is the only mouse connexin known to be expressed in these parts of the adult conductive tissue and is thus considered as a marker of the conduction system. In the present report, we investigated CX40 expression and distribution during mouse heart development. We first demonstrate that CX40 mRNA is regulated throughout development, as are other heart connexin transcripts, i.e., CX37, CX43, and CX45, with a decreasing abundance as development proceeds. We also show that the CX40 transcript and protein are similarly regulated, CX40 being expressed as two different phosphorylated and un‐phosphorylated forms of 41 and 40 kDa, respectively. Surprisingly, distribution studies demonstrated that CX40 is widely expressed in 11 days post‐coitum (dpc) embryonic heart, where it is detected in both the atria and ventricle primordia. As development proceeds, the CX40 distribution pattern in the atria is maintained, whereas a more dynamic pattern is observed in the ventricles. From 14 dpc onwards, as the adult ventricular conduction system differentiates, CX40 decreases in the trabecular network and it is preferentially distributed in the ventricular conduction system. CX40 is thus the marker of the early differentiating conduction system. It is hypothesized that the conduction system is present in unorganized “embryonic” form at 11 dpc and trans‐differentiates by 14 dpc into the adult conduction system. © 1995 wiley‐Liss, Inc.
Formation of new myotubes occurs exclusively at the multiple innervation zones of an embryonic large muscle
Authors: Duxson M. J. , Sheard P. W.
Published: February 2005

This work examines the general principle of whether production of embryonic muscle fibres is invariably linked to sites of innervation, as we have previously reported in small rodent muscles (Duxson et al. [1989] Development 107:743–750). The experimental strategy has been to make a detailed electron microscopic analysis of the formation of new myotubes in a large muscle having multiple, discrete innervation zones. The particular model system is the guinea pig sternomastoid muscle, a strap‐like, parallel‐fibred muscle with four distinct endplate bands, both in the embryo and the adult. Primary myotubes in the developing muscle extended from tendon to tendon of the muscle and were innervated at each of the multiple endplate zones. Each point of innervation of the primary myotubes was a focus around which many new secondary myotubes formed, and each secondary myotube was approximately centred on one of the innervation sites of its supporting primary myotube. This confirms our previous report, in rat IVth lumbrical muscle, of an invariable association between sites of formation of new secondary myotubes and sites of innervation. We suggest that, in vivo, nerve terminals either directly induce the initial myoblast fusions which give rise to new secondary myotubes, or induce some precondition for fusion. An alternative hypothesis is that a common patterning influence in the muscle localizes both innervation and secondary myotube formation to the same zone. The pattern of secondary myotube production in the embryo has important implications for the size and final architecture of muscles in larger animals, and some of these are discussed. © 1995 wiley‐Liss, Inc.
Cdk family genes are expressed not only in dividing but also in terminally differentiated mouse germ cells, suggesting their possible function during both cell division and differentiation
Authors: Rhee Kunsoo , Wolgemuth Debra J.
Published: February 2005

The roles of the cyclin dependent kinase (Cdk) family in murine germ cell development have been examined by studying the expression of five Cdk family genes (Cdc2, Cdk2, Cdk4, Pctaire‐1, and Pctaire‐3) in mouse reproductive organs. Northern blot and in situ hybridization analyses revealed distinctive expression patterns of these genes with striking cellular, lineage, and developmental stage specificity. We observed Cdk expression in cell types with proliferative activity: Cdc2 and Cdk2 expression in premeiotic spermatocytes in the testis, and Cdc2, Cdk2, and Cdk4 expression in granulosa cells of ovarian follicles. Cdc2 transcripts were most abundant in late pachytene to diplotene spermatocytes, soon to undergo meiosis. Surprisingly, we also observed expression of Cdk family genes in non‐proliferating cell types. All five Cdk family genes examined were expressed in Sertoli cells of the adult testis, which are no longer mitotically active. With regard to Pctaire‐1 and Pctaire‐3, the highest levels of expression were observed in postmeiotic spermatids. Immunoblot analysis also revealed the presence of high levels of Pctaire‐1 in postmeiotic germ cells. These results suggest that Cdk family kinases may exhibit various functions in germinal and somatic cells during gametogenesis, not only in the cell cycle but also in other regulatory processes, including differentiation. © 1995 wiley‐Liss, Inc.
Primary structure of the long and short splice variants of mouse collagen XII and their tissue‐specific expression during embryonic development
Authors: Böhme Kathrin , Li Yefu , Oh Paul S. , Olsen Bjorn R.
Published: February 2005

Type XII collagen, a member of the FACIT group of extracellular matrix proteins, consists of molecules that are trimers of α1(XII) chains. The three chains in each molecule form a cross‐shaped structure with a central globule from which a triple‐helical tail and three finger‐like regions (containing von Willebrand factor A‐like domains and fibronectin type III repeats) extend. cDNA cloning/sequencing of chicken α1(XII) collagen and protein studies with mouse, bovine, and human material suggest that the α1(XII) collagen gene gives rise to two molecular variants, differing in the length of the finger‐like regions, by alternative splicing of the primary transcript. To provide a basis for studies of the function of the two variants in an organism that can be genetically manipulated, we have isolated and sequenced mouse cDNAs encoding both splice variants. The sequence provides the first complete nucleotide and amino acid sequence of mammalian type XII collagen. From these cDNAs we have generated digoxigenin‐labeled RNA probes for in situ hybridization of developing mouse embryos to find out whether the splicing mechanism responsible for generation of the two forms is developmentally regulated. The results, combined with Northern blot and RT‐PCR analysis of RNA from embryos at various developmental stages, demonstrate that the long form of collagen XII, XIIA, is the predominant form at early stages (ED7 and 11); at later stages of development (ED15 and 17) the short form, XIIB, becomes the major form. As the short form becomes the major product, the long splice variant continues to be expressed in several tissues, even after birth. An exception is dermis, which is positive for the long form up to embryonic day 15, but negative at day 18, when only the short form RNA can be detected. © 1995 wiley‐Liss, Inc.
Differential effects of retinoic acid and a retinoid antagonist on the spatial distribution of the homeoprotein Hoxb‐7 in vertebrate embryos
Authors: López Silvia L. , Dono Rosanna , Zeller Rolf , Carrasco Andrés E.
Published: February 2005

An antibody raised against the recombinant Xenopus laevis Hoxb‐7 protein (López and Carrasco [1992] Mech. Dev. 36:153–164) recognizes the 30 kDa translation product of the Hoxb‐7 gene in X. laevis and the cognate nuclear protein in chicken embryos. The X. laevis Hoxb‐7 protein was expressed maternally and zygotically. Treatment of X. laevis and chicken embryos with either all‐trans retinoic acid (RA) or the retinoid antagonist Ro 41–5253 (Ro; Apfel et al. [1992] Proc. Natl. Acad. Sci. U.S.A. 89:7129–7133) during early development induced malformations of the neural tube and complementary changes in the expression domain of the homeoprotein Hoxb‐7. Treatment of X. laevis embryos with retinoic acid during gastrulation induced an anterior shift of the Hoxb‐7 expression domain and was correlated with an enlargement of rhombomere r7. In addition to a reduction in rhombomere numbers and of forebrain size, various malformations involving all three germ layers were observed. Treatment of X. laevis embryos with the antagonist Ro before or during gastrulation caused a progressive reduction of the Hoxb‐7 domain and also dose‐dependant malformations of all three germ layers. RA or Ro treatment of chicken embryos from the beginning of gastrulation caused changes of the Hoxb‐7 expression domain very similar to those observed in X. laevis. In particular, either a dose‐dependant loss of the Hoxb‐7 protein in the neural tube or an ectopic expressionin the forebrain region was observed. The results of this study indicate that endogenous retinoids regulate the spatial expression of homeobox‐containing genes in vertebrates. © 1995 wiley‐Liss, Inc.
The density of organic and volatile and non‐volatile inorganic components of bone
Authors: Gong J. K. , Arnold J. S. , Cohn S. H.
Published: February 2005

Densities of the various bone fractions i.e., water, organic, volatile inorganic and ash fractions, as well as fat in the various animals have been studied. However. values reported by various workers failed to show consistency and uniformity, especially with respect to the volatile inorganic (often called “CO2 fraction”) and the ash fractions. These densities are prerequisite to the study of the volumetric composition of bone and bone marrow.

In our study, the fat and organic densities found were similar to those previously reported. The volatile and non‐volatile inorganic (ash) fractions, had density values of 1.684 and 3.180, respectively. The ash density was much higher than values previously reported but it verifies a theoretical value deduced by the authors from published work.

Our higher ash density was due to a smaller measured volume of this fraction obtained by applying a negative pressure to remove the small entrapped air bubbles from the ash sample prior to the water displacement measurement. Because a smaller portion of the total inorganic volume was used for the ash calculation, giving it a higher density, a larger balance of the total inorganic volume was left for the volatile inorganic density calculation. This accounted for ash and volatile inorganic densities which were higher and lower, respectively, than such values previously reported.

Prior to the determination of the density of the non‐volatile inorganic fraction, the ashing time and temperature were studied. Curves plotted from the results of such studies were described and explained.
Composition of trabecular and cortical bone
Authors: Gong J. K. , Arnold J. S. , Cohn S. H.
Published: February 2005

A technique was devised for obtaining marrow‐free trabecular bone so that the trabecular and cortical bone composition of dog, steer, monkey and man could be studied. Vertebral body was cut in the frontal plane into slices 2 mm thick with an electric band saw. The cortical bone encrircling each slice was trimmed off with a cleaver, leaving intact a lacy slice of trabecular bone. The marrow substance was washed away by fine and powerful jets of tap water obtained from an adjustable nozzle. Marrow washing was discontinued when no trace of red color was visible on holding the slice in front of a strong light source.

The quantities of water, volatile inorganic, organic and ash fractions in cortical bone was alike for all species. Likewise, the trabecular bone fractions of each was quantitatively similar. In general, density and amount of ash in cortical bone was higher than that in trabecular bone. The water and ash:organic ratio were higher in trabecular than in cortical bones.

Ratios of trabecular to cortical ash for the bones in an entire dog skeleton were also determined. Based on this, volume or mass of the various bone fraction may be estimated when the weight of the ash for any particular bone is known.
Histochemical studies of the human fetal thyroid during the first half of fetal life
Authors: Shepard Thomas H. , Andersen Helge , Andersen Henning J.
Published: February 2005

A number of histologic and histochemical techniques have been used to study 42 human fetal thyroids from fresh specimens ranging in crown‐rump length from 22 to 201 mm. Three periods of differentiation (colloid production) were defined. The first or precolloid stage was found in fetuses of 22 to 65 mm and consisted of strands of compact epithelial cells separated by loose connective tissue which contained only a few vessels. The early colloid production period from 65 to 80 mm was characterized by the appearance of small accumulations of colloid in the center of the follicles. The blood vessels between follicles increased during this period. In the last period during maturation of the colloid cavities, the spaces between the epithelium were more reduced and almost completely filled with blood vessels. No change in the average cell height was found during differentiation.

With differentiation, the nuclei of epithelium became less compact and RNAase‐removable cytoplasmic material increased. Also of interest was the marked decrease in glycogen at the time of colloid production.

The staining characteristics of the early colloid showed little change during the period studied. The colloid was stained by the following reagents: periodic‐acid Schiff, mercury organge, toluidine, ninhydrin‐Schiff, Millon's and Sakaguchi's. The larger colloid spaces took slightly more toluidine stain than the smaller ones.

The enzyme reaction for alkaline phosphatase was found only in the vascular system, and acid phosphatase was found in the cytoplasm of epithelium and, especially in the differentiated specimens, it was concentrated at the apex of the cell. Lactic and succinic dehydrogenase activity did not seem to change with maturation and was located in the cytoplasm around the nucleus and toward the apex of the cell.

Thin rays of colloid‐like material were observed to radiate out between cells from early colloid cavities. Based on unpublished electron microscopic data, organ cultures of human thyroid and observations from the developing chick, these spaces probably represent intercellular dilatations which have been filled with colloid from the central cavity. These spaces may be a secondary or safety mechanism which allows the circumference of the follicle to increase in size.
Electron microscopy after rapid freezing on a metal surface and substitution fixation
Authors: van Harreveld A. , Crowell Jane
Published: February 2005

A method for rapid freezing is described in which use is made of the good heat conducting properties of silver. The freezing was accomplished by bringing the tissue in contact with a polished silver surface at the temperature of liquid nitrogen either at atmospheric or reduced pressure. Helium gas flowing over this surface prevented the condensation of water or air on the silver. After freezing the tissue was placed in a substituting solvent. The best results were obtained with 2% osmium tetroxide in acetone at −85°C. The ultrastructure of the tissue was well preserved in a narrow surface layer only.
The proliferative activity of the adrenal cortex using a radioautographic technic with thymidine‐H3
Authors: Hunt Thomas E. , Hunt Eleanor A.
Published: February 2005

Proliferative activity of the adrenal cortex was studied following injections of thymidine‐H3. Normal male Long‐Evans rats had less activity than comparable animals of the Sprague‐Dawley strain. Of the Long‐Evans rats killed at different hours of the day, those injected with thymidine‐H3 at 6 P.M. and killed six hours later had the greatest activity. Normal male rats 35 to 73 days of age had almost all activity in the glomerulosa and outer fasciculata of the cortex. This activity was greatly increased two or three days after injecting colchicine, compound 48/80, or carbon tetrachloride. Such stressing agents did not cause any increase in activity during the first 24 hours. Three days after carbon tetrachloride a considerable increase in proliferative activity occurred in the inner zona fasciculata and reticularis of the adrenal of female rats during diestrus. Male rats killed 28 to 40 days after injecting thymidine‐H3 showed no evidence of centripetal migration of cells into the reticularis during that time. The absence of centripetal migration and the marked responsiveness of the inner fasciculata and reticularis of female animals after stressing agents supports the zonal theory of function in the adrenal cortex.
Thymus gland fractionation and thymocyte lysis
Authors: Schneider Rose Mary
Published: February 2005

Methods are described for the isolation of two separate fractions from guinea pig thymus gland; i.e., Hassall's corpuscles and stromal segments. Hassall's corpuscles are relatively dense epithelial aggregates sedimentable at low centrifugal acceleration, while the lighter stromal segments remain in the supernatant fluid. Solubilization of the thymocytes, effected by high‐speed homogenization in hypertonic glycerol, is unaccompanied by visible gelation or nuclear residue. Glycerol‐sensitivity resembles radiation‐sensitivity in many respects.
Epiphyseal ossification and shaft elongation in human metatarsal bones
Authors: Roche Alexander F.
Published: February 2005

Measurements of the lengths of the shafts of the third, fourth and fifth metatarsals have been made on serial standarized radiographs of white Australian children. A statistical analysis showed that, in the boys, there were no real differences between the rates of elongation of the shafts during periods when the corresponding epiphyses became radio‐opaque and those that occurred during earlier or later periods. There was a statistically significant tendency in the girls for rate of elongation of metatarsals to be more rapid before radio‐opaque changes in epiphyses were noted than after.
On the innervation of the blood vessels in the human foot
Authors: Mustalish Anthony C. , Pick Joseph
Published: February 2005

With the aid of a Zeiss operation microscope, a dissection was made of the nerves to the blood vessels of the dorsum and sides in the two feet of the cadaver of an adult man. No obvious vascular nerve issued from the saphenous nerve. The terminations of the dorsal metatarsal and interdigital arteries and veins over the two medial thirds of the dorsum of the foot were supplied by extremely thin nervelets which originated chiefly from the medial branch of the superficial peroneal nerve. The sural nerve issued conspicuous filaments to the lateral interdigital and metatarsal blood vessels, to the lateral calcaneal arteries and to the talo‐calcaneal region. These findings provided a firmer anatomical basis for the interruption of the vascular nerves of the dorsum and sides of the foot by blocking with analgesic agents or by crushing the superficial peroneal, sural and saphenous nerves above the ankle.
Glomerular localization of intravenous Alcian blue
Authors: Parsons Donald A. , McManus J. F. A.
Published: February 2005

The anatomical and histological picture following intravenous injections of several concentrations of aqueous solutions of Alcian Blue has been described. Alcian Blue granules can be found in all cases within the reticulo‐endothelial cells of the body in lungs, spleen, liver and bone marrow and in the kidney.

The greatest concentration of the dye is found within the renal glomeruli. It is in such concentration as to enable one to see individual glomeruli with the 10 × magnification of the dissecting microscope. On high power (950 ×) the dye can be seen as granules within the endothelial cells and podocytes of the glomerulus, as well as in the cells of the glomerular stalk. No Alcian Blue has been identified within the macula densa.

Certain difficulties due to the solubility of the dye in sections are mentioned. Present means of meeting them are covered. Also discussed are follow‐up studies being undertaken and possible implications of the procedure.
The ultrastructure of human embryonic myocardium
Authors: Leak L. V. , Burke J. F.
Published: February 2005

Human embryonic myocardial tissues ranging from eight to eighteen weeks of development were prefixed and dissected in buffered formaldehyde, postfixed in buffered OsO4 and processes for Epon embedding. At these stages of development the myocardial cells contain an abundance of sarcoplasm with a sparse random distribution of myofibrils that frequently appear branched. The A, I and Z bands exhibited in the adult myocardial cells are also observed in these stages of development. However, the M line is only slightly apparent, while no H band was observed. The mitochondria are not arranged in parallel arrays as found in the adult, but appear to be randomly distributed throughout the interfibrillar sarcoplasm. An array of tubules, cisternae and vesicles that comprise the sarcoplasmic reticulum is also distributed throughout the interfibrillar sarcoplasm. In some areas this tubular system appears as vesicles with small dense granules along its outer surface, while in other areas it appears smooth. The distribution and orientation of the sarcoplasmic reticulum is far less pronounced in the embryonic stages examined in this study than that reported for the adult myocardium. Dense granules (150 to 350 Å) appear as clusters or aggregates of granules in the sarcoplasm and are similar to the glycogen granules described by other investigators. The intercalated disc is observed at the junction of two opposing cells and occurs with less frequency than the intercalated disc in the adult myocardium.
Myocardial fiber size and capillary‐fiber ratio in the right and left ventricles of the rat
Authors: Angelakos E. T. , Bernardini P. , Barrett W. C.
Published: February 2005

Histological techniques were used to obtain fiber counts, capillary counts, fiber diameters, and capillary‐fiber ratios in the adult rat heart. Based on measurements of 3,600 fibers in six rats, the means and standard deviations of the fiber diameters for the left and right ventricles were 11.8 ± 4.8 and 11.5 ± 4.3 μ respectively. The corresponding capillary‐fiber ratios were 0.92 ± 0.23 and 0.90 ± 0.33. The differences between the right and left ventricles were not statistically significant. Statistical analysis was used to evaluate the reproducibility of the results. The frequency distribution of the fiber diameters was found to be unimodal in both right and left ventricles suggesting that only one group of fiber sizes is involved. It was found that fiber counts could be used as an indication of fiber size under ordinary conditions provided that the total number of fibers counted is over 200.
The histochemical distribution of β‐galactosidase activity in the ovary and female genital tract
Authors: Bulmer D.
Published: February 2005

In the female genital system of the rat the only organ to give a strong histochemical reaction for β‐galactosidase with the post‐coupling technique is the ovary, where strong staining occurs in the corpora lutea, the interstitial cells and some of the macrophages. In the uterus and vagina the relatively weak reaction is restricted to the epithelia, and is reduced by ovariectomy. During pregnancy the decidua shows marked activity, but in the portions of the uterus which are not involved in placentation the reaction is still restricted to the epithelium. The mucified vaginal epithelium of late pregnancy is moderately reactive. In the rabbit ovary the activity is strong, with intense staining in interstitial cells; in the ovaries of the guinea pig and monkey it is much weaker.

Though β‐galactosidase is considered to be mainly lysosomal, its ovarian distribution differs in some respects from the distribution of acid phosphatase. The relative intensities of the ovarian and uterine reactions in the rat, as shown histochemically, do not appear to correspond with biochemical findings.
The pelvic and perineal fasciae and their neural and vascular relationships
Authors: Roberts W. H. , Habenicht James , Krishingner Gene
Published: February 2005

This study was based upon a dissection of the pelvic fasciae and associated structures of one hundred and three adult pelves as well as those of three full term fetuses. The perineal fasciae and their neural and vascular relationships were studied in an additional 55 specimens.

The uterovaginal fascia, as stated by others, is a well‐defined structure. One is usually able, on the basis of a fascial cleft, to distinguish readily between the fascial sheath of rectum proper and the deeper layer of subperitoneal fascia, called by some the presacral fascia. The latter is described, including the relationship of the pelvic autonomics thereto. The relationship of the vesical branches of the pelvic plexus and of the venous plexuses to the terminal ureter are also described.

We were able to confirm the presence of a superficial and a deep perineal fascia; the latter forms the inferior boundary of the superficial perineal space proper, as described by others. The relationship of particular nerves (and vessels) to the fascial planes of the perineum follows a definite pattern even when variation from the normal is present.
Action of the pterygoideus muscle during feeding in the lizard Uromastix aegyptius (Agamidae)
Authors: Throckmorton Gaylord S.
Published: February 2005

The actions of the deep and superficial portions of the ptery‐goideus muscle and the depressor mandibulae were studied in the agamid lizard, Uromastix aegyptius, using fine wire electrodes. The EMG signals were recorded, while simultaneously recording the jaw positions during feeding on movie film at 32 fps. Muscle activity varies with different types of food. The deep and superficial portions of the pterygoideus performed different functions. The deep ptery‐goideus functioned during opening of the jaws, presumably to protract the jaw. The superficial pterygoideus was strictly a jaw elevator. The depressor mandibu‐lae is not the initiator of jaw opening. When biting on tough food items, the deep pterygoideus and depressor mandibular were active.
Extracellular coat in developing human palatal processes: Electron microscopy and ruthenium red binding
Authors: Meller Samuel M. , Barton Lorraine H.
Published: February 2005

The prefusion epithelium of human palatal processes was examined for evidence of specialization which might facilitate epithelial adherence with the opposing palatal process. A surface coat stained with ruthenium red (RR) was found on all apical aspects of the palatal epithelium. In the prefusion regions, RR staining was also observed in the spaces between the superficial cells of the epithelium and in necrotic cells. Adjacent oral and nasal epithelium excluded the RR below the level of the apical junctional complex. In the absence of RR, a dense material was observed in the most superficial intercellular spaces of the prefusion region. Many superficial cells in the area were in various stages of necrosis. The combination of degenerating surface cells and an accumulation of a poly‐anionic substance such as glycoprotein may facilitate epithelial adherence between opposing human palatal processes.
Experimental studies on the acetylcholinesterase‐positive nerves in the ovary of the rat
Authors: Burden Hubert W. , Lawrence Irvin E.
Published: February 2005

Adrenergic and acetylcholinesterase (AChE)‐positive nerves were studied in the rat ovary four days after various experimental denervation procedures. Ablation of pelvic parasympathetic nerves (pelvic neurectomy [PN]) or abdominal vagotomy (AV) had no obvious affect on the adrenergic or AChE‐positive nerves in the ovary. Section of the mesovarium resulted in the loss of all histochemically demonstrable adrenergic and AChE‐positive nerves. Chemical sympathectomy with 6‐hydroxydopamine (6‐HD) resulted in the loss of all histo‐chemically demonstrable adrenergic nerves. A few AChE‐positive nerves remained in the hilar and medullary regions following chemical sympathectomy. When the presumptive parasympathectomy procedures (AV and PN) were combined with chemical sympathectomy, again no adrenergic nerves remained, however a few hilar and medullary AChE‐positive fibers persisted after sympathec‐tomy plus PN, but no AChE‐positive fibers were demonstrable in the AV plus 6‐HD group.

These findings show that most of the AChE in ovarian nerves is localized in adrenergic nerves. It is suggested that the few AChE‐positive fibers remaining in the ovarian hilar area after 6‐HD treatment or 6‐HD plus PN are derived from the vagus. These few AChE‐positive nerves may be postganglionic vagal parasympathetic or they may be sensory fibers.