bluuebunny/crossref_metadata_2025 huggingface dataset:
Early encounters of the repetitive kind: A prelude to cell adhesion in conjugating Tetrahymena thermophila
Authors: Brown Frederick , Tirone Sunlian , Wolfe Jason
Published: February 2005

The relationship between direct cell contacts and subsequent cell‐cell adhesion was studied in the ciliated protozoan, Tetrahymena thermophila. During sexual reproduction, adhesion into pairs begins at approximately 1 hr after mixing starved complementary mating types. However, direct contacts between cells prior to pairing are known to be required for the development of adhesion‐readiness. We find here that the initial contact interactions are necessary but not sufficient to drive the cells to adhesion‐readness. Secondary interactions are needed.

Two distinct experimental strategies were used. First, we examined the effects of a mutant that is unable to pair but which can stimulate two different wild‐type mating type cells to pair when mixed. We showed that stimulation by the mutant is only partial; in response to mutant cells, wild‐Type cells ceased forming food vacuoles but did not undergo tip transformation or concanavalin A (Con A)‐receptor tipping. Further, kinetic analysis shows that when mixed together, pair‐formation among partially stimulated wild‐type cells is slightly delayed, allowing time for these pre‐pairing processes to occur. This indicates that, beyond the initial contact interaction, mutant‐stimulated wild‐type cells require a subsequent interaction which cannot be fulfilled by the mutants. Secondly, we found that by blocking contact interactions between wild‐type mating types at various time intervals after they were mixed, additional increase in tip transformation and Con A receptor tipping was prevented. Further, both processes underwent a regression. This indicates that multiple contact interactions are required to drive the cells to adhesion readiness and to prevent developmental slip‐back. © 1993 wiley‐Liss, Inc.
Re‐evaluating the role of astrocytes in blood‐brain barrier induction
Authors: Holash J. A. , Noden D. M. , Stewart P. A.
Published: February 2005

Neural tissue induces brain capillary endothelial cells to express a diverse array of characteristics that allow them to regulate the passage of solutes between the blood and the brain; these features are collectively referred to as the blood‐brain barrier (BBB). Because astrocytes are intimately associated with brain capillaries, they have been thought to be the cell type responsible for barrier induction. Widely accepted support of this hypothesis has been derived from experiments showing that astrocytes implanted into the anterior chamber of the rat eye, or onto the chorioallantoic membrane of the chicken embryo, remain unstained by circulating Evan's blue, while grafts of fibroblasts in these sites stain intensely.

We have found several limitations associated with placing grafts in either site, leading us to believe that previously reported results are inconclusive. Astrocytes implanted into the anterior chamber form grafts that are poorly vascularized, whereas fibroblast grafts are richly vascularized by vessels which are often fenestrated. This likely accounts for apparent differences in vessel permeability reported by others. We have found that iridial vessels associated with astrocyte grafts do not change their ultrastructure to resemble brain capillaries.

Grafting of cells to the chorioallantoic membrane elicits an extensive inflammatory response. Inflammation results in poor delivery of tracers to graft vasculature as well as altering vessel permeability. Treatment of hosts with steroidal anti‐inflammatory agents in doses compatible with survival of the host does not resolve the inflammatory response but does allow improved graft survival. Even after treatment with anti‐inflammatory agents, however, astrocyte graft vasculature fails to express high levels of a barrier marker, the GLUT‐1 isoform of the glucose transporter. Transplantation of avascular embryonic spinal cord, that induces robust vessel ingrowth and GLUT‐1 expression in intra‐embryonic vessels, was unable to elicit the ingrowth of more than a few vessels from the chorioallantoic membrane vasculature, and none of these expressed glucose transporter. We conclude that the anterior chamber and chorioallantoic membrane are not suitable sites for studying BBB induction, and that there is, at present, no conclusive evidence that mature astrocytes play a significant role in the initial expression of the BBB. © 1993 Wiley‐Liss, Inc.
Development of the vasculature of the anterior pituitary: Ontogeny of basic fibroblast growth factor
Authors: Schechter Joel E. , Pattison Amy , Pattison Tim
Published: February 2005

This study correlates the ontogeny of basic fibroblast growth factor (FGF) with the development of the vasculature of the anterior pituitary (AP) in two strains of rat, Sprague‐Dawley (SD) and Fischer 344 (F344). Immunolocalization of FGF was followed from the first appearance of Rathke's pouch (RP) in 12‐day (12d) fetuses, through each day of fetal development, and in 5, 20, and 50d postnatal female rats. In addition, the ontogeny of folliculo‐stellate cells (FSC) is described, since previous studies suggested that these unique cells might function as phagocytes in the regulation of FGF. In both rat strains, vascularization of the AP commenced in 16d fetuses. In 15–20d fetuses, dense foci of immunopositivity for extracellular FGF were apparent at sites of capillary penetration adjacent to partially disrupted, immature gonadotropes. Localization of FGF was first detected in immature gonadotropes in 18d fetuses and persisted in the cytosol of a subpopulation of gonadotropes thereafter. In 15d fetuses, FGF was localized within the cytosol intimately associated with the peripheral‐facing plasma membranes of all cells of the adenohypophysis, and persisted to variable degrees in later fetal stages. Localization of FGF within nuclei of AP parenchymal cells was evident only in 16–17d fetuses. Although the ontogeny of FGF and vascularization of the AP was very similar in both rat strains, the ontogeny of FSC differed markedly. In both strains, follicular lumens contained FGF during late fetal and early postnatal development. However, both electron microscopy and immunostaining for S‐100 marker protein revealed that the postero‐lateral edges of the AP of F344 rats often lacked FSC when compared to SD rats, a situation which could compromise regulation of FGF by FSC at the AP periphery in that strain, and thereby contribute to the neovascularization from systemic blood vessels known to occur in that strain during prolactinoma formation. © 1993 Wiley‐Liss, Inc.
In situ hybridization studies suggest a role for the basic region‐leucine zipper protein hXBP‐1 in exocrine gland and skeletal development during mouse embryogenesis
Authors: Clauss Isabelle M. , Gravallese Ellen M. , Darling Jama M. , Shapiro Fred , Glimcher Melvin J. , Glimcher Laurie H.
Published: February 2005

The spatial and temporal distribution of transcripts for the TRE/CRE‐binding basic region‐leucine zipper protein hXBP‐1 was determined by in situ hybridization. Analysis of embryos from day 10.5 to 18.5 pc revealed high level expression of hXBP‐1 RNA in two developing organ systems: (1) in bone and cartilage cells of the developing skeleton and toothbuds, and (2) in exocrine glands including the pancreas and the submandibular and salivary glands. High level expression was also found in whisker follicles and in selected cells in brown adipose tissue. In the developing skeleton, hXBP‐1 RNA was expressed starting on day 11.5 pc in osteoblasts of newly formed intramembranous bone. Thereafter, hXBP‐1 was expressed in both osteoblasts and preosteoblasts in bone formed directly by intramembranous formation as well as in bone formed during endochondral ossification. The most intese signal was observed in preosteoblasts and osteoblasts of newly forming bone. At day 11.5 pc low level hXBP‐1 expression was also observed in matrix secreting chondroblasts of bones which are formed initially of cartilage, at the stage where they consist entirely of cartilage, at the stage where they consist entirely of cartilage. Signal was also present in matrix producing chondroblasts of the mature zone of the growth region during endochondral ossification although at significantly lower level than in osteoblasts. hXBP‐1 is thus the first transcription factor described, to our knowledge, whose level of expression is modulated during the osteoblast developmental sequence in vivo. The pattern of expression of hXBP‐1 in the developing skeleton was found to be very similar to that of the genes encoding the tissue inhibitor of metalloproteinase and alkaline phosphatase throughout development. These observations suggest that hXBP‐1 may play a role in regulating the expression of tissue specific genes (TIMP, osteonectin, osteopontin, osteocalcin) expressed in osteoblasts. It is intriguing that the promoter regions of several such genes contain potential hXBP‐1 binding sites. © 1993 Wiley‐Liss, Inc.
Failure to make normal α ryanodine receptor is an early event associated with the Crooked Neck Dwarf (cn) mutation in chicken
Authors: Airey Judith A. , Baring Martha D. , Beck Claudia F. , Chelliah Yogarany , Deerinck Thomas J. , Ellisman Mark H. , Houenou Lucien J. , McKemy David D. , Sutko John L. , Talvenheimo Jane
Published: February 2005

We have investigated the molecular basis of the Crooked Neck Dwarf (cn) mutation in embryonic chickens. Using biochemical and pharmacological techniques we are unable to detect normal α ryanodine receptor (RyR) protein in intact cn/cn skeletal muscle. Extremely low levels of αRyR immunoreactivity can be observed in mutant muscles, but the distribution of this staining differs from that in normal muscle and colocalizes with the rough endoplasmic reticulum immunoglobulin binding protein, BiP. This suggests the existence of an abnormal αRyR protein in mutant muscle. In day E12 cn/cn muscle the levels of RyR mRNA are reduced by ∼80%, while the levels of other muscle proteins, including the α1 subunit of the dihydropyridine receptor, the SRCa2+‐ATPase, calsequestrin, and glyceraldehyde‐3‐phosphate dehydrogenase, and their associated mRNAs are essentially normal in cn/cn muscle. There is also a failure to express αRyR in cn/cn cerebellar Purkinje neurons. Expression of the βRyR, a second RyR isoform, is not initiated in normal skeletal muscle until day E18. In cn/cn skeletal muscle significant muscle degeneration has occurred by this time and the βRyR is found at low levels in only a subset of fibers suggesting the reduced levels of this isoform are a secondary consequence of the mutation. The cardiac RyR isoform is found in cn/cn cardiac muscle, which contracts in a vigorous manner. In summary, a failure to make normal αRyR receptor appears to be an event closely associated with the cn mutation and one which may be largely responsible for development of the cn/cn phenotype in embryonic skeletal muscle. © 1993 Wiley‐Liss, Inc.
Differentiation of mouse embryonic stem cells in vitro: III. Morphological evaluation of tissues developed after implantation of differentiated mouse embryoid bodies
Authors: Chen Una , Kosco Marie
Published: February 2005

Mouse embryonic stem cells (ES) were allowed to differentiate in a liquid culture system. After 2–3 weeks, complex cystic embryoid bodies developed. These bodies were composed of several structures identified as cardiac muscle and yolk sac blood islands as well as cupshape compartments containing a mixed population of hematopoietic stem cells. When these cystic embryoid bodies were implanted into adult mice, either subcutaneously or under the kidney capsule, they developed into various tissues. These included bone, blood vessels, cardiac muscle, nerves, and skin with hair follicles. In addition, highly differentiated, complicated tissues resembling intestinal epithelium with mucus glands or salivary glandular tissue were derived. The ES tissues from these in vitro developed embryoid bodies developed quickly within 2 to 3 weeks of implantation. This is in contrast to a minimal of 6 weeks for teratocarcinomas derived from embryonic carcinoma cells and/or the direct implantation of undifferentiated embryonic stem cells. Moreover, we found that there are different types of tissue developed upon different sites of implantation. The data suggest a local environment and/or growth factors are influential for ES tissue development. This system provides a possible means to purify and identify stem cells that give rise to specific tissues, and to study the factors regulating the commitment of these stem cells. © 1993 Wiley‐Liss, Inc.
The Etl‐1 gene encodes a nuclear protein differentially expressed during early mouse development
Authors: Schoor Michael , Schuster‐Gossler Karin , Gossler Achim
Published: February 2005

Recently, we isolated a novel mouse gene, Etl‐1 (Enhancer‐trap‐locus‐1), whose deduced amino acid sequence shows in its C‐terminal portion striking homology to the brahma protein (BRM), a transcriptional regulator of homeotic genes in Drosophila, and to SNF2/SWI2, a transcriptional regulator of various genes in Saccharomyces cerevisiae. Here we report the generation of antibodies against the Etl‐1 gene product (ETL‐1) and describe the subcellular localization as well as the expression and distribution of the ETL‐1 protein during mouse pre‐ and early post‐implantation development. ETL‐1 is a nuclear protein and is expressed in a biphasic manner during early embryogenesis. Moderate levels of ETL‐1 were detected in unfertilized and fertilized eggs but in the latter the protein was not concentrated in the pronuclei and seemed evenly distributed throughout the cytoplasm. In two‐cell embryos nuclear ETL‐1 protein accumulated transiently and levels decreased during subsequent cleavage development. After the morula stage, ETL‐1 levels increased again; in blastocysts high levels of ETL‐1 were present in inner cell mass cells whereas trophectoderm cells contained little or no ETL‐1. During subsequent development essentially all cell types except parietal endoderm and trophoblast cells contained high levels of ETL‐1. Our results imply that nuclear ETL‐1 is dispensable for the progression to the two cell stage, and suggest that during cleavage ETL‐1 might be needed at the onset of embryonic transcription. In blastocysts ETL‐1 function might be specifically required in cells of the inner cell mass and later in most cells of the embryo proper and extraembryonic ectoderm lineage. © 1993 Wiley‐Liss, Inc.
Induction of neuronal differentiation by planar signals in Xenopus embryos
Authors: Sater Amy K. , Steinhardt Richard A. , Keller Ray
Published: February 2005

The induction of the central nervous system in amphibian embryos is mediated both by early planar signals produced by mesoderm at the dorsal lip and later vertical signals emanating from the dorsal mesoderm after involution. We have examined the role and spatial extent of planar signals in the induction of neuronal differentiation. Planar explants that included only the deep layer of the dorsal marginal zone, comprising both the dorsal mesoderm and the contiguous dorsal ectoderm, were isolated at the beginning of gastrulation. After removal of the epithelial layer, explants were maintained in modified Danilchik's medium until mid‐neurula stages, when they were transferred to modified Danilchik's medium + 0.1% bovine serum albumin and cultured on laminin. Neurite outgrowth occurred in 90% of these planar explants. In contrast, little or no neuronal differentiation occurred in either ventral planar explants or explants of ectoderm alone. Video analysis of cell movements shows that large‐scale cell mixing does not occur between mesoderm cells and ectoderm cells in planar explants. Retrograde labelling of neuronal cell bodies indicates that cells throughout the ectoderm undergo neuronal differentiation; neurons also differentiate in cultures of distal ectoderm isolated at early neurula stages from planar explants prepared at the beginning of gastrulation. These observations indicate that planar signals act over an extended range to induce neuronal differentiation. The inductive capacity of vertical signals was examined by recombining animal caps from ultra‐violet (UV) irradiated embryos with involuted mesoderm from normal midgastrula embryos. Differentiation of either neurons or anterior neural structures occurred in 73% of vertical recombinates. Our results demonstrate that planar signals from the dorsal lip of the blastopore are capable of inducing neuronal differentiation over a considerable distance in the absence of epithelial confinement, convergence and extension, and mixing between the mesoderm and ectoderm. © 1993 Wiley‐Liss, Inc.
Developmentally regulated and spatially restricted antigens of radial glial cells
Authors: Herman Jean‐Paul , Victor John C. , Sanes Joshua R.
Published: February 2005

Radial glial cells, present in many parts of the embryonic vertebrate central nervous system (CNS), have been implicated in the guidance of neuroblasts from the ventricular zone to their laminar destinations. Moreover, radial glial cells may be progenitors of some CNS neurons and glia. To gain new insight into the structure and development of these cells, we have generated and characterized a panel of monoclonal antibodies that recognize radial glial cells of the chick optic tectum. Mice were immunized with hommogenates of embryonic day (E) 10 tectum, and antibodies were analyzed by immunofluorescence and immunoblotting. We describe here three pairs of antibodies. (1) H5 and a previously generated antibody, R5 (Dräger et al., J. Neurosci. 4:2025, 1984), stain the whole extent of the radial glial cell from E7 to E20. In cultures prepared from E10 tecta, both stain a filamentous meshwork in glial cells but not in neurons. On immunoblots, both recognize a protein of ∼52 kD that is closely related (or identical) to vimentin. (2) H28 and H29 stain radial glia between E7 and E14, but not later. Moreover, H28 and H29 staining is markedly more intense in the ventricular and intermediate zones than in the laminae of the tectal plate. Both of these antibodies recognize an intracellular epitope in cultured glial cells and a protein of ∼35 kD on immunoblots. (3) H2 and H27 recognize antigens concentrated in the most superficial processes and endfeet of radial glia in late (E16–E20) embryos. They stain distinct structures in cultured glia, suggesting that they recognize distinct antigens. H27 recognizes a protein of ∼29 kD on immunoblots. Thus antibodies H5 and R5 are good markers of radial glial cells at all stages, whereas the others define antigens that are developmentally regulated and localized to discrete domains. Together, these antibodies can be used to study temporal and spatial specializations of radial glia. © 1993 Wiley‐Liss, Inc.
Selective expression of the chicken platelet‐derived growth factor α (PDGFα) receptor during limb bud development
Authors: Potts Jay D. , Carrington Jill L.
Published: February 2005

Platelet‐derived growth factor (PDGF) affects proliferation and differentiation of chicken limb bud mesoderm in vitro. However, no PDGF receptor has been characterized in the chicken wing bud in vivo. In this study, we used reverse transcription PCR (rtPCR), Northern blot analysis, and Western blot analysis to identify a molecule, in the developing wing bud, which represents the chicken homolog of the PDGFα receptor. The chicken PDGFα receptor mRNA was present in both mesoderm and ectoderm and all stages of the developing limb bud examined. Cultured limb bud mesoderm also expressed the PDGFα receptor transcript. In addition, the PDGFα receptor protein was present in whole limb buds and cultured limb bud mesoderm. Expression of the PDGFα receptor in cultured mesoderm was independent of the presence of ectoderm cells. The relative sizes of both the mRNA and protein for the PDGFα receptor in the chicken limb bud were similar to mammalian counterparts. Using similar approaches, neither the mRNA nor protein representing the chicken homolog of the PDGFβ receptor was detected. These data demonstrate for the first time that a PDGFα receptor is present in the embryonic chicken limb bud and may help regulate growth and differentiation of the embryonic limb. © 1993 Wiley‐Liss, Inc.
Fibroblast behavior in the embryonic chick heart
Authors: Choy Michael , Oltjen Sharon , Ratcliff Dorothy , Armstrong Margaret , Armstrong Peter
Published: February 2005

Intracardiac fibroblasts (mesenchymal cells) of Hamburger and Hamilton stage 36 chick heart reside in the epicardium and atrioventricular valves. The characteristics of the epicardial fibroblasts include segregation from the myocytes of the heart wall myocardium, voluminous extracellular matrix production, and some cell proliferation activity. The atrioventricular fibroblasts intermingle with myocytes at the mutual border between these tissues, produce smaller amounts of extracellular matrix, and show very active cell proliferation. Is the behavior of each population of fibroblasts predetermined or is each responding in a reversible fashion to local environment? A cell aggregate culture system, which permits 3‐dimensional cell‐cell and cell‐matrix interactions, is used to study the behaviour of each isolated population of fibroblasts in vitro. In the presence of serum‐free medium, each population produces very little extracelluar matrix, has relatively low mitotic activity, and does not segregate from myocytes when the aggregate is composed of randomly intermixed myocytes and fibroblasts. In the presence of chicken serum, each population increases matrix production, increases cell proliferation, and sorts from myocytes. Thus, we suggest that the two populations of fibroblasts in the developing heart are responding to local environments and the differences observed in vivo are not the consequence of irreversible states of cellular differentiation. © 1993 Wiley‐Liss, Inc.
Developmental patterns of two α1(IX) collagen mRNA isoforms in mouse
Authors: Liu Chia‐Yang , Olsen Bjorn R. , Kao Winston W.‐Y.
Published: February 2005

Northern blot hybridization, reverse‐transcription polymerase chain reaction (RT‐PCR), and RNase protection assays were used to examine the expression of twoα1(IX) collagen mRNA species (long and short form) in developing mouse tissues. Furthermore, in situ hybridization was used to identify cells expressing the Col9a1 gene during eye development. The results indicate that during embryonic development eye and heart preferentially express the short form; lung and cartilage express the long form; whereas liver expresses a very low level of long formα1(IX) mRNA which can only be detected by RT‐PCR. In situ hybridization demonstrated that at 10.5 day postcoitum (d.p.c.), theα1(IX) collagen mRNAs were first expressed in optic cup (neural ectoderm) but not in lens vesicle (surface ectoderm). By 13.5 d.p.c., the cells that express theα1(IX) mRNA progressively were concentrated to ward the anterior part of the neural retina. By 16.5–18.5 d.p.c., the hybridization signals were found exclusively in the inner non‐pigmented layer of the presumptive ciliary epithelium. As ciliary epithelial cells become well differentiated 3 weeks after birth, cells expressing the Col9a1 gene were limited to the junction between mature ciliary folds and the neural retina. No hybridization signal could be detected in ocular tissues of mouse older than 6 weeks. It is of interest to note that a hybridization signal was not detected in cornea at the various developmental stages examined, suggesting that mouse cornea does not significantly expressα1(IX) mRNA during embyronic development. This differs from that of chick cornea development. In summary, the expression of the Col9a1 gene shows a temporospatial pattern throughout mouse eye development. It is suggested that the short form collagen IX may play an important role in eye development. © 1993 Wiley‐Liss, Inc.
Tissue interactions with underlying dura mater inhibit osseous obliteration of developing cranial sutures
Authors: Opperman Lynne A. , Sweeney Thomas M. , Redmon Julie , Persing John A. , Ogle Roy C.
Published: February 2005

Cranial sutures play a critical role in calvarial morphogenesis, serving as growth centers during skull development. Both biomechanical tensile forces originating in the cranial base and biochemical factors present in dura mater have been postulated as determinants of suture morphogenesis and patency. A rat transplant model free of the putative biomechanical influence of the dura and cranial base was used to investigate the role of the dura mater in both the initial morphogenesis and maintenance of sutures during skull growth. Day 19 fetal presumptive (F19) and day 1 neonatal differentiated (N1) coronal sutures, including associated frontal and parietal bones, were transplanted with or without underlying dura mater to the center of adult parietal bones. After 1, 2, and 3 weeks, transplanted tissues were examined histologically and histomorphometrically to determine whether sutures formed and whether they were obliterated by ossification in the absence of dura mater. Both F19 and N1 sutures remained patent for 2 weeks either in the presence or the absence of transplant dura mater. However, at 3 weeks, in the absence of transplant dura mater, sutures were obliterated by bone, while in the presence of dura mater sutures resisted ossification, demonstrating an essential requirement for interactions with the transplant dura mater in maintaining functional sutures. Both F19 and N1 transplants showed comparable bone growth (cross‐sectional surface area), regardless of the presence of transplant dura mater. These experiments suggest that tissue interactions of a biochemical nature, rather than biomechanical forces generated through the cranial base, are required to maintain the suture as a non‐ossified growth center. Furthermore, while the presence of dura mater was essential for maintenance of suture patency, fetal dura mater was not required for initial suture formation. © 1993 Wiley‐Liss, Inc.
Prevention of spinal neural tube defects in the curly tail mouse mutant by a specific effect of retinoic acid
Authors: Chen Wei‐Hwa , Morriss‐Kay Gillian M. , Copp Andrew J.
Published: February 2005

Curly tail mouse mutant embryos (ct/ct) develop spinal neural tube defects (NTD) in 54% of cases, comprising isolated tail flexion defects and spina bifida with tail flexion defects. Both types of spinal NTD result from delayed closure of the posterior neuropore (PNP). Previous studies (Seller et al. [1979] Proc. R. Soc. Lond. Biol. 206:95–107; Seller and Perkins [1982] Prenat. Diagn. 2:297–300) described a paradoxial effect of retinoic acid (RA) on the phenotypic expression of the ct mutation: Treatment with low doses of RA on day 8 of gestation increased the incidence of total NTD, whereas low doses of RA administered on day 9 resulted in reduced incidence of total NTD. In order to investigate further the reported preventive effect of RA, we have carried out detailed analyses of the effects of maternal treatment with 5 mg/kg RA on the incidence of NTD at different developmental stages, and on the development and growth of ct/ct embryos. We found that 5 mg/kg RA reduces the incidence of spinal NTD in a stage‐specific manner, without increasing the incidence of cranial NTD. The effect of RA is specific: There were no other alterations in morphogenesis, growth, development, resorption rate, or litter size. RA was more effective in the prevention of isolated tail flexion defects than of spina bifida. Prevention of isolated tail flexion defects was maximal (50% reduction) when RA was administered between 10 days 4 hours and 10 days 8 hours post coitum (p.c.) inclusive (24 to 34 somite stage). In contrast, maximal prevention of spina bifida (36%) resulted from RA administration at 10 days 8 hours p.c.; decreased PNP size in treated embryos, compared with control embryos, was evident by 6 hours after the treatment at the 27 to 31 somite stage. The preventive effect of RA on spina bifida was related to maternal phenotype: By comparison with phenotypically straighttailed mothers, curly‐tailed mothers had a greater incidence of spina bifida among their offspring, and this incidence was unresponsive to RA. This result suggests that additional factors, such as modifier genes, modulating phenotypic expression of the ct gene, may be present in the ct mutant stock. Here we show that the RA prevention of spinal NTD is a specific effect. Hence it is plausible that this prevention of spinal NTD by RA is mediated via nuclear retinoic acid receptors. © 1994 Wiley‐Liss, Inc.
Deficient outgrowth of the ureteric bud underlies the renal agenesis phenotype in mice manifesting the limb deformity (ld) mutation
Authors: Maas Richard , Elfering Sandra , Glaser Tom , Jepeal Lisa
Published: February 2005

Mice which are homozygous for the limb deformity (ld) mutation also manifest an incompletely penetrant unilateral or bilateral renal agenesis phenotype. Intercross experiments suggest that the differences in penetrance of the renal agenesis phenotype between homozygous mice with different ld alleles are due to intrinsic differences in the strength of the mutant alleles or to one or more closely linked modifying loci, and not to generalized differences in genetic background. Analysis of ld/ld embryos between embryonic days 11–13 reveals delayed outgrowth or complete absence of the ureteric bud, the inducer of metanephric mesenchyme. Since explants of ld/ld metanephric mesenchyme differentiate in culture when apposed to embryonic spinal cord, we conclude that deficient ureteric bud outgrowth is the morphologic basis for renal agenesis in ld/ld mice. However, since ld transcripts can be detected in both metanephric mesenchyme and ureteric bud, the molecular basis for the deficiency in ureteric bud outgrowth could reside in either component. © 1994 Wiley‐Liss, Inc.
Developmental expression of human cartilage matrix protein
Authors: Mundlos S. , Zabel B.
Published: February 2005

Cartilage matrix protein (CMP) is a non‐collagenous component of cartilage with a yet unknown function. In this study we used in situ hybridization to investigate the temporal and sptial distribution of CMP transcripts during human embryonic and early fetal development, and compared it to the pattern of expression observed for collagen types I, II, X, and decorin. The distribution of CMP and collagen type II transcripts followed a similar pattern in the embryonic bone anlage, the fetal growth plate, and the developing vertebral column. Expression was highest in the upper hypertrophic and lower proliferative zone, whereas calcified cartilage was negative throughout the different stages of bone development. Chondrocytes of calcified cartilage, however, were not quiescent but expressed collagen type X. The onset of collagen type X expression was linked to hypertrophy and occurred before calcification became apparent. In contrast, deorin and collagen type I were highly expressed in bone and perichondrium but not in growth plate cartilage. During the development of the synovial joints a different pattern of expression emerged. After formation of the joint cavity, there was a halt in expression of CMP but not of collagen type II in chondrocytes close to the articular surface. A band of CMP negative chondrocytes covering the joint surface was observed in all joints investigated. Decorin mRNA was demonstrated in the reserve zone adjacent to the joints, but not in articular cartilage. Extraskeletal expression of CMP was observed in the embryonic retina. The results demonstrate the differential expression of CMP during human skeletal development and chondrocyte differentiation. The distribution of CMP transcripts is unique and distinct from other known matrix genes. © 1994 Wiley‐Liss, Inc.
Complex patterns of expression suggest extensive roles for the α2β1 integrin in murine development
Authors: Wu Justina E. , Santoro Samuel A.
Published: February 2005

The extracellular matrix plays important roles in embryogenesis. The integrin family of adhesion receptors may mediate critical cellular interactions with the extracellular matrix during development. In this study, we elucidated the developmental spatial and temporal expression pattern of the α2β1 integrin heterodimer, a cell surface receptor for collagens and laminin. We generated reagents for studying the α2β1 integrin and examined the developmental expression of the integrin in postimplantation mice. A partial length murine α2 cDNA was isolated and the protein encoding region was found to be 82% homologous to that of the human α2 cDNA. A synthetic peptide corresponding to the carboxy‐terminus of murine α2 was used to generate α2‐specific antiserum. The antiserum and riboprobes derived from both the α2 cDNA and the previously characterized murine β1 subunit cDNA were used to determine the spatiotemporal expression of the α2 subunit by immunocytochemistry and of the α2 and β1 mRNAs by in situ hybridization. Both approaches gave concordant results. Expression of the α2 integrin subunit was observed in both the maternal and embryonic components of the placenta, namely the perivascular and basal zone decidual cells and decidual cells and spongiotrophoblasts at the maternal/embryonic junction. Expression was also observed in cells actively producing and remodeling the extracellular matrix in the maternal uterus and in the developing gut, lens, cartilage, bone, and tooth of the embryo. Generally, expression of the α2 integrin subunit was found in cells entering their later stages of differentiation such as in chondrocytes as they became hypertrophic, ameloblasts and odontoblasts as they became columnar and began to secrete the matrix of the tooth, endothelial cells after they formed tubules, in the lens just prior to and during lens fiber production, and in the collecting ducts of the kidney only after full gestation. Throughout embryogenesis, β1 mRNA was widely distributed and present in cell types expressing α2 mRNA and protein. The developmental expression pattern of the α2β1 integrin suggests roles for the integrin in placental development and matrix assembly and remodeling. © 1994 Wiley‐Liss, Inc.
Localized epiphyseal dysplasia in offspring of manganese‐deficient rats
Authors: Hurley Lucille S. , Asling C. Willet
Published: February 2005

Development of a characteristic localized dysplasia of the proximal tibial epiphysis, occurring in high incidence in offspring of manganese‐deficient rats, was studied. Young of female rats, maintained from weaning on a diet deficient in manganese, were compared with those of females receiving the same diet with manganese supplementation. Epiphyses were studied histologically and in alizarin‐stained specimens. In offspring of deficient females, the proximal tibial epiphyseal ossification center appeared at the normal time (10–12 days). Soon thereafter, abnormalities were observed; in particular, spicules of osseous and marrow tissue connecting the epiphysis to the metaphysis through the epiphyseal plate were seen. By 21 to 48 days of age, all of 19 deficient offspring showed marked abnormalities. In over 30%, the epiphysis seemed absent when viewed from the external aspect; when examined at the internal (split) surface, a tiny epiphysis was found recessed into a pocket‐like depression in the metaphysis and partially fused with it. Even when “pocketing” was incomplete, the epiphysis was small, misshapen, poorly vascularized, fragmented, and showed rarefaction. Bony spicules frequently perforated the narrowed plate. Abnormalities of the cartilage were often seen. Offspring of deficient mothers transferred to the manganese‐supplemented diet late in gestation also showed some defects of this epiphysis. Possible mechanisms related to the pathogenesis of this disorder are discussed, and a hypothesis is proposed.
The calcified zone (basal layer) of articular cartilage of rabbits
Authors: Mankin Henry J.
Published: February 2005

In the mammalian embryo, the articular end of a long bone consists of a mass of fetal cartilage which undergoes transformation into two types of tissue as the animal ages: The hyaline cartilage surface of the adjacent joint; and the bone of the ossific nucleus of the epiphysis. The junction of these two areas, the calcified zone (or basal layer) of the articular cartilage, was studied in the distal femur of 110 albino rabbits of various ages by: tritiated thymidine autoradiography; routine histologic staining and mitotic counts; special stain for glycogen; and special stain for calcium (murexide).

In the immature rabbit (under two months) the cartilage cells are arranged in columns and there is evidence of active proliferation. In its most basal portion adjacent to the vascular tufts of the epiphyseal nucleus, the cells are hypertrophic and contain glycogen. The intervening matrix bars are calcified. It is apparent that, at this age, endochondral ossification, indistinguishable from that at the epiphyseal plate, is occurring.

In the older rabbit (age four months) proliferation, columniation, and glycogen content are minimal, and the basal layer of cartilage is diffusely calcified. Proliferation is intense in and about the capillary loops and a thin layer of bone surrounds the capillary.

In the adult (over six months) rabbit, calcification and ossification predominate. No proliferative activity is noted. Apparently growth has ceased completely or is so slow as to be unmeasurable by available techniques.
Genetic influences on induced cleft palate in different strains of mice
Authors: Loevy Hannelore
Published: February 2005

This paper reports some of the genetic aspects of induced cleft palate susceptibility in the Strong a mouse compared with another less susceptible strain (C3H) and with their intercrosses.

Pregnant females were injected with 1.25 mg of cortisone (Cortone acetate Merck) daily on the eleventh, twelfth, thirteenth and fourteenth day of pregnancy and killed on the seventeenth and eighteenth day of pregnancy. The control animals were not treated.

In treated animals, cleft palate was induced in 100% of the Strong a offspring and 36.3% in the C3H offspring. In cross matings between these two strains the same dose of cortisone induced 11.7% of cleft palate if the mother was of the Strong a strain and 43.7% if of the C3H strain. The same dose produced cleft palate in 29.7% of the offspring of the F1 generation when mated among themselves and in 42.5% of the white offspring of the F2 generation when mated among themselves.

The incidence of induced cleft palate was independent of albinism in the offspring of the F1 and F2 generation. There was no significant correlation between the occurrence of cleft palate and the position in utero, the weight of the affected fetuses or the litter size; however, the more crowded the uterine horn, the more affected fetuses it contained.

There was no significant correlation between weight of the mother and number of affected fetuses among her offspring when the effect of litter size was eliminated.
Development of parabiosis intoxication in rat parabionts
Authors: Binhammer R. T. , Epstein S. , Whitehouse A.
Published: February 2005

The development of parabiosis intoxication, primary symptoms of which are anemia of one animal and concomitant hyperemia of the other, was sequentially followed in Holtzman (Sprague‐Dawley) — Charles River (Sprague‐Dawley) parabionts. Hemoglobin and hematocrit determinations, RBC, reticulocyte and WBC counts were done on blood removed from pairs by cardiac puncture. In addition bone marrow total nucleated cell counts were done, systolic blood pressure measurements were taken and cross circulation rates were studied with Cr51 tagged erythrocytes. Intoxication developed rapidly in these distantly related pairs about 10 days after union and terminated in death or breakdown of the union by 21 days. The anemia, which was not limited to one or the other partner, was accompanied by reticulocytosis and normal nucleated bone marrow cell counts indicating no suppression of marrow function. The anemic partner also showed total white cell counts elevated over those in the hyperemic partner at 13 days after union. The partner destined to become hyperemic showed elevated systolic blood pressure concomitant to the change in erythrocyte values suggesting that no causal relation exists between blood pressure and the development of intoxication. Cross circulation rates tested with Cr51 tagged erythrocytes showed slowing of circulation evident as early as nine days after parabiosis. Some pairs maintained circulation rates similar to controls for as long as 15 days, but in the majority cross circulation had virtually ceased by this time.
Adrenergic synaptic vesicles in the anterior hypothalamus of the rat
Authors: De Iraldi A. Pellegrino , Duggan H. Farini , De Robertis E.
Published: February 2005

After formaldehyde perfusion a small area of the anterior hypothalamus was extirpated, identified neuroanatomically and studied under the electron microscope.

The preparative technique consisted in refixation of the piece in 1% osmium tetroxide for two hours, immersion in 2% uranyl acetate and embedding in Epon 812. Sections were stained with lead acetate.

The main areas comprised in the tissue were the nucleus hypothalamicus anterior, nucleus periventricularis inferior and anterior hypothalami area.

In the neuropiles of these regions varicose axons containing neurotubules and granular vesicles are observed. There are also numerous nerve endings containing typical synaptic vesicles in addition to some having a dense granule of reduced osmium. Measurements demonstrate that there are two different populations of vesicles with means of 510 Å and 1,300 Å respectively.

The possible significance of the granular vesicles is discussed and related to the high content of catecholamines in this region of the CNS. The possibility that these nerve endings may synthesize and store more than one transmitter substance is also discussed. The wide variety of vesicles found in axons and synaptic endings of the anterior hypothalamus is also considered as supporting a unified theory of neurosecretion postulated by one of the authors.
An electron microscopic study of the effects of reserpine on adreno‐medullary cells of the syrian hamster
Authors: Yates Robert Doyle
Published: February 2005

Adult Syrian hamsters were given daily subcutaneous injections of reserpine (1 mg/kg) for one or three days in order to study the fine structural changes in adreno‐medullary cells. Initial alterations of fine structure in animals given one injection and sacrificed 15 hours later. Hamsters treated for three days were adrenalectomized on the left side 24 hours after the last reserpine injection. Following adrenalectomy, animals were allowed to recover for 48 or 96 hours after which the cells of the right adrenal medulla were compared with those of the left.

Medullary cell changes 15 hours following one injection of reserpine included partial loss of electron opaque granules and an increase in the number of cytoplasmic vesicles and vacuoles. Medullary cells from the left adrenal glands removed following three subcutaneous injections of reserpine were characterized by a marked loss of electron opaque granules and by the presence of many vesicles and vacuoles distributed throughout the cytoplasm.

Forty‐eight hours following unilateral adrenalectomy medullary cells from the remaining right glands exhibited slightly electron opaque granules within the cytoplasm, each of which was surrounded by a smooth surfaced membrane. Cytoplasmic vesicles and vacuoles had decreased in number. Ninety‐six hours following unilateral adrenalectomy medullary cells from the right glands showed further decreases in numbers of vesicles and vacuoles, and granules which possessed an electron opaqueness comparable to control medullary cells had reappeared within the cytoplasm.
A method for demonstrating subserous lymphatics with hydrogen peroxide
Authors: Parke Wesley W. , Michels Nicholas A.
Published: February 2005

The visualization of the subserous lymphatics of various organs is rapidly accomplished by the topical application of hydrogen peroxide. As the peroxide reacts with a natural inclusion of the lymph, presumably catalase, the vessels are spontaneously inflatedwith free oxygen. This method is much easier to use than injection techniques as fresh material, catheterization of the vessels, or tissue puncture are not required.
Morphological characteristics of the anterior mesenteric artery of fowl
Authors: Ball R. A. , Sautter J. H. , Katter M. S.
Published: February 2005

The anterior mesenteric artery of two species of fowl, the turkey and chicken, is found to differ structurally from the basic pattern observed in other avian arteries and in mammalian arteries in general. This difference in structure lies in the fact that the avian anterior mesenteric artery contains two well‐developed muscular components: an inner circular, and an outer longitudinal, analogous to the arrangement of the muscularis externa of the intestinal wall. However, the evidence presented indicates that the outer longitudinal layer is part of the adventitia. The possible functional significance of this feature is discussed.
The postnatal development and differentiation of the boundary tissue of the seminiferous tubule of the rat
Authors: Leeson C. Roland , Leeson Thomas S.
Published: February 2005

The morphology of the boundary tissue of the seminiferous tubule of the rat has been investigated in testes from animals aged from birth to four months. In the adult, the boundary tissue consists of four layers: (1) an inner non‐cellular layer comprising a network of collagen fibrils sandwiched between two basement membranes (2) an inner cellular layer of flattened cells showing many of the characteristics of smooth muscle, including intracytoplasmic filaments and micropinocytotic vesicles, (3) an outer non‐cellular layer containing scattered colagen fibrils and associated usually with a single basement membrane and (4) an outer cellular layer, component cells of which contain no fine filaments. At birth, the seminiferous tubule rests upon a basement membrane which separates it from a layer of low cuboidal cells. External to this, there is a narrow intercellular zone containing scattered fibrillar material and a region consisting of numerous processes of mesenchyme cells. By ten days postnatal, four definite layers are established due to the differentiation of an outer cellular layer of flattened cells from the mesenchyme, and intracytoplasmic filaments have made their appearance within the inner cellular layer. In subsequent stages there is progressive thinning and specialization of the cellular layers and increased fibril content within the non‐cellular layers. By 22 days postnatal the boundary tissue appears virtually adult in morphology.
Electron microscopy of post‐mortem changes in the rat myocardium
Authors: Hibbs Richard G. , Black William C.
Published: February 2005

An electron microscopic study was made on specimens of rat myocardium taken at various intervals after death, in order to determine the extent and character of autolytic change occurring during the first ten hours. Specimens were taken immediately after death and at 15 minutes, one hour, three hours, five hours and ten hours after death, fixed in 1% phosphate‐buffered osmium tetroxide and examined with the electron microscope.

The first noticeable change was a rapid depletion of glycogen. The specimens taken one hour or more after death show a longer sarcomere length indicating a more relaxed state. This is believed to reflect the inability of these fibers to contract upon stimulation by the initial contact with the fixative. Nuclei, when encountered, showed more chromatin clumping than in fresh tissue, but the nuclear membranes were intact.

Very little change was noted in the mitochondria, sarcoplasmic reticulum, or other cellular components.