bluuebunny/crossref_metadata_2025_split huggingface dataset:
The appearance and distribution of intermediate filament proteins during differentiation of the central nervous system, skin and notochord of Xenopus laevis
Authors: Godsave S. F. , Anderton B. H. , Wylie C. C. 
Published: April 2021

ABSTRACT
Antibodies against various intermediate filament proteins have been used to follow cell differentiation in the early Xenopus embryo. Three new monoclonal antibodies against Xenopus cytokeratins raised against Triton-insoluble material from tadpoles (RD35/2a, RD35/3a and D3/3a), two antibodies against mammalian cytokeratins (LE65 and LP3K), monoclonal anti-(rat 200K neurofilament protein), rabbit anti-(rat glial filament acidic protein), and rabbit antibodies to hamster and calf vimentin were used. We show that cytokeratins are present in the early central nervous system (CNS) and persist in the ependymal cells of the adult CNS. We also show that the notochord contains cytokeratin. The ontogeny of intermediate filament protein appearance in the CNS, skin and notochord between neural fold stage and swimming tadpole stage are described. These results are discussed in particular with regard to the use of the antibodies as differentiation markers.
Evaluation of the roles of intrinsic and extrinsic factors in occlusion of the spinal neurocoel during rapid brain enlargement in the chick embryo
Authors: Desmond Mary E. , Schoenwolf Gary C. 
Published: April 2021

ABSTRACT
The spinal neurocoel normally occludes during the second day of chick embryogenesis as the lateral walls of the spinal cord become apposed closely in the midline. Concomitantly, the brain initiates its rapid and substantial enlargement. Occlusion, although short-lived, might play a major role in brain enlargement. As a result of occlusion, the brain ventricles are sealed off from the external milieu prior to closure of the posterior neuropore, establishing a closed fluid-filled system. The present study focuses on the mechanisms of occlusion of the spinal neurocoel. We tested two postulated intrinsic factors (microtubule-mediated neuroepithelial cell elongation and microfilament-mediated apical neuroepithelial cell constriction) and five extrinsic factors (three mediad pushing forces generated by the somites, perineural extracellular matrix and expanding surface ectoderm; and two stretching forces generated either vertically by pulling of the elongated notochord or longitudinally by elongation of the embryo) in maintaining occlusion. Our results suggest that occlusion is maintained by other, untested intrinsic factors and/or by forces generated within a perineural collar, composed of cellular and extracellular materials, intimately associated with the basal aspects of the spinal cord. Cytoskeletal-mediated changes in cell shapes, pushing forces and vertical and longitudinal tensions are not involved. Further studies are needed to examine the intrinsic properties of the neuroepithelium and the factors initiating occlusion and reopening.
The role of ultimobranchial bodies in the modulation of the response of chick embryos to 1,25-dihydroxy-cholecalciferol
Authors: Narbaitz Roberto , Rad Jaffar Soleimani 
Published: April 2021

ABSTRACT
Ultimobranchial bodies (UBBs) were dissected from 17-day-old chick embryos and grafted onto the chorioallantoic membrane of 8-day-old embryos. The embryos with UBB grafts as well as sham-grafted controls were injected on the 10th day of incubation with 100 ng 1,25(OH)2D3 dissolved in ethyl alcohol or with an equal volume of ethyl alcohol alone; embryos were sacrificed on the 13th day. Grafted UBBs showed ultrastructural characteristics typical of actively secreting glands. A histological study of the tibiae from all embryos showed that while the grafted embryos responded to the injection of 1,25(OH)2D3 with a peripheral rim of undermineralized bone trabeculae, sham-grafted embryos never did so. These results confirm the original hypothesis that the presence of differentiated UBBs is a precondition for the production of undermineralized bone (osteoid) by 1,25(OH)2D3.
In a second series of experiments, similarly treated embryos were sacrificed on the 10th, 11th, 12th and 13th day; the levels of calcium and inorganic phosphate were determined in their blood. The injection of 1,25(OH)2D3 produced in all embryos hypercalcaemia and hypophos-phataemia. However, the hypophosphataemic response was more prolonged in the embryos with UBB grafts than in sham-grafted ones. These results suggest that the grafted UBBs prolonged the hypophosphataemic response, probably by secreting calcitonin and thus reducing the rate of bone resorption. It is also probable that the prolonged hypophosphataemia produced or contributed to the undermineralization of the peripheral (subperiosteal) trabeculae.
Is maternal mRNA a determinant of tissue-specific proteins in ascidian embryos?
Authors: Jeffery W. R. , Bates W. R. , Beach R. L. , Tomlinson C. R. 
Published: April 2021

ABSTRACT
The generation of different cell types during embryonic development is thought to be mediated by the combined activity of cytoplasmic factors (determinants), which are localized in the egg, and inductive interactions, which occur between different embryonic cells and tissues. Ascidians, animals that exhibit rapid and exceptionally autonomous development (reviewed by Jeffery, 1985), appear to employ cytoplasmic determinants to generate embryonic cell diversity. Although determinants have not been identified in ascidians or other animals, it is hypothesized that they function in at least two different ways. First, as initially pointed out by Morgan (1934), determinants may be regulatory factors which promote differential gene expression in specific cell lineages. Consistent with this possibility, inhibitors of transcription, added prior to gastrulation, block the appearance of some ascidian tissue-specific enzymes and morphological markers whose expression is regulated by the activity of cytoplasmic determinants (Whittaker, 1973; Crowther & Whittaker, 1984). Second, determinants may be localized factors which promote cell diversification independent of zygotic gene expression. This class of determinants is implicated in specifying crucial embryonic events that occur before the onset of zygotic transcription. Evidence for the second class of determinants in ascidians was first obtained from interspecific hybridization studies. These studies showed that haploid andromerogones, which developed from anucleate eggs of one ascidian species fertilized with sperm of another species, exhibited larval adhesive papillae that were morphologically identical to those of the maternal species (Minganti, 1959).
Manipulating the anteroposterior pattern of the Drosophila embryo
Authors: Frohnhófer Hans Georg , Lehmann Ruth , Nüsslein-Volhard Christiane 
Published: April 2021

ABSTRACT
The establishment of pattern and polarity in the insect egg has been studied intensively using a variety of experimental approaches. Drosophila, while the system of choice for genetic analysis of pattern formation has been rather neglected as an experimental organism and species with longer developmental time and larger eggs were preferred in classical studies. Among the dipteran insects, midges such as Chironomous and Smittia with their transparent chorion and synchronous development were found more rewarding. The classical methods of ligation, puncture, transplantation, destruction or removal of material, and centrifugation were applied to eggs of a variety of insect species. Although the degree of response to experimental manipulation was found to be widely different, there were similarities in the type of abnormal patterns produced by the various treatments which suggested more general conclusions:-the anteroposterior pattern is probably controlled by two centres of activity, localized at the anterior and posterior egg pole respectively, with a long-range effect on the entire egg axis (reviewed by Sander, 1976).
Effects of zinc deficiency on morphogenesis of the fetal rat eye
Authors: Rogers John M. , Hurley Lucille S. 
Published: April 2021

ABSTRACTMaternal zinc deficiency during pregnancy results in a high frequency of fetal eye malformations in the Long-Evans rat. In this study we examine the development of the eye from days 12 through 21 of gestation in conceptuses of dams fed deficient or adequate levels of zinc and also examine maternal plasma and conceptus zinc concentrations during this period. Dams were fed diets containing 0·5 (0·5 Zn group), 4·5 (4·5 Zn group), or 100 (100 Zn AL group) μg zinc per gram diet ad libitum, or 100 μg zinc g−1 diet in amounts restricted on a daily basis to the intake of matched animals from the 0-5 Zn group (100 Zn RI group). Conceptuses were removed and maternal plasma was collected on days 12, 14, 16, 19 and 21 of gestation. Maternal plasma and conceptus zinc concentrations reflected maternal dietary zinc level, with dam plasma Zn concentrations in the order of 0·5 Zn group &lt; 4·5 Zn group &lt; 100 Zn group on all days. A similar pattern held for embryo/fetus zinc, except for days 19 and 21, at which times the 0·5 Zn and 4·5 Zn fetuses had similar zinc concentrations. Histological examination of the developing eye of 0·5 Zn fetuses on days 12 and 14 revealed that invagination of the optic cup was often deficient, and that closure of the choroid fissure did not occur, resulting in colobottiata and retinal folding visible at term. A very few fetuses were found at term to be anophthalmic or have only remnants of ocular tissue. In the absence of coloboma, retinal histogenesis evaluated on day 19 appeared normal in zinc-deficient fetuses, and in fact, the eye was relatively spared the effects of zinc deficiency in these fetuses. No eye malformations were seen in 4·5 Zn fetuses. Thus, low maternal plasma and embryonic zinc concentrations during organogenesis adversely affect morphogenesis of the optic vesicle and closure of the choroid fissure, leading to anophthalmia or colobomatous microphthalmia with retinal folding at term. A possible mechanism for the latter malformation involving lack of vitreous pressure necessary for normal expansion of the developing eye is discussed. When the choroid fissure does close normally, later prenatal histogenesis of the retina does not seem to be adversely affected by zinc deficiency.
The upright position of brush border-type microvilli depends on myosin filaments
Authors: Temm-Grove Constance , Helbing Dirk , Wiegand Christiane , Höner Bernd , Jockusch Brigitte M. 
Published: April 2021

ABSTRACT
We have studied the correlation between the actomyosin organization and microvillar position in an epithelial cell line derived from the proximal pig kidney tubule (LLC-PK1). When grown on glass, these cells are approximately 5-6 μm in height and develop numerous microvilli that project from the dorsal membrane. A fairly homogeneous distribution of microvilli was achieved by synchronization of the cell cycle. These microvilli are of the brush border type, as defined by their content of villin and their anchorage in a myosin-rich terminal web-like structure. When LLC-PK1 cells were injected with two monoclonal antibodies against pig brain nonmuscle myosin, in concentrations yielding a 1:1 ratio of antibody to myosin, neither microvillar number nor length was affected. However, when we examined the cells by scanning electron microscopy 1-3 h after microinjection, we found that one of the antibodies (a-PBM 4) had a profound effect on microvillar position: more than 50% were seen tilted or lying prone on the plasma membrane. The microvilli of cells injected with the other antibody (a-PBM 9) were not significantly different from those of cells injected with control antibodies. This difference correlates with in vitro properties of the antibodies: a-PBM 4 decreases the actin-activated Mg 2+ -ATPase of pig brain nonmuscle myosin quite substantially, while a-PBM 9 affects it only moderately. These differential effects are probably a consequence of the different epitope location as determined for both antibodies, not of differences in antibody affinity. Our data are compatible with the hypothesis that a-PBM 4 also interferes with the actomyosin interaction in situ, thus decreasing the effective crosslinking of microvillar rootlets by myosin filaments in the terminal web. On the basis of this model, we suggest that myosin filaments are essential for the upright position of brush-border type microvilli.
The interendothelial junction in myocardial capillaries: Evidence for the existence of regularly spaced, cleft-spanning structures
Authors: Schulze Charlotte , Firth J. Anthony 
Published: April 2021

ABSTRACT
Water and hydrophilic solutes cross the endothelium of continuous capillaries via the paracellular cleft and possibly other routes. This pathway shows a selectivity to molecule size and charge. However, it is not yet known which systems confer this selectivity.
Isolated rat hearts were perfusion-fixed through the coronary circulation, stained with lanthanum or tannic acid, and further processed for transmission electron microscopy. Thin sections viewed at X 160,000 magnification revealed regularly spaced, cleft-spanning structures in the wider zone of a small percentage of clefts in addition to at least one zonula occludens. Goniometric tilting of the specimen in steps of 5° perpendicular to the plane of the wide zone showed that such “linkers” can be revealed in at least 40% of all clefts. They become visible at some tilt angles, although the same area of the cleft is featureless at other angles. Single linker spacing measurements were obtained using a computerized image analysis system, and compiled in a frequency distribution chart. On the basis of these data, two models of a regular linker distribution within the cleft are illustrated. Our results provide evidence for the presence of regularly spaced, cleft-spanning structures within the interendothelial cleft which may have implications for endothelial cell-cell adhesion and permeability.
The 9E3 protein: immunolocalization in vivo and evidence for multiple forms in culture
Authors: Martins-Green M. , Aotaki-Keen A. , Hjelmeland L. M. , Bissell M. J. 
Published: April 2021

ABSTRACT
The avian gene 9E3/CEF4 belongs to a group of genes whose products are highly conserved and are homologous to inflammatory mediators. These genes, sometimes referred to as the gro family, are also expressed upon wounding or serum-stimulation of quiescent cells, suggesting that they may be important in aspects of growth and/or wound healing. We have used an antibody to the product of the 9E3 gene to show for the first time the distribution in vivo of the protein of one of these genes. The polyclonal antibody was produced against a synthetic peptide, [Cys76], 9E3, (77-103), located at the carboxy end of the molecule. The specificity of the antibody was determined by transfection of the 9E3 cDNA into Cos 7 cells, which do not express this gene. Moreover, despite the high homology between 9E3 and IL-8, the antibody did not crossreact with this molecule. The antibody was used to immunoprecipitate the protein from cultured normal and RSV-transformed chick embryo fibroblasts (CEFs) and to determine its distribution in tissues of newly hatched chicks. The staining was abundant in the cells and extracellular matrix (ECM) of connective tissue and other tissues of mesenchymal origin, such as bone and tendon. Most cells in the granulation tissue of wounds stained, some more intensely than others; the ECM also stained, expecially in areas of scar tissue where collagen is abundant. In RSV-induced tumors, the protein was absent except in necrotic areas where a few cells -potentially macrophages -stained. In general, as expected, the protein was present in the cells and tissues that expressed the mRNA, but there were exceptions. In the smooth muscle layer of arteries and the epidermis of the skin, where the levels of mRNA were too low to be detected by in situ hybridization with a radioactively labeled probe, the protein was present. The antibody immunoprecipated a 14 kDa molecule from the cell extracts of normal and transformed CEFs, and two forms (9 kDa and 6 kDa) from the supernatant of RSV-transformed CEFs. The results presented here suggest that this protein could play a role in tissue remodeling and wound healing.
Hyaluronan-dependent cell migration can be blocked by a CD44 cytoplasmic domain peptide containing a phosphoserine at position 325
Authors: Peck David , Isacke Clare M. 
Published: April 2021

ABSTRACT
CD44 is the principle transmembrane receptor for the extracellular matrix glycosaminoglycan hyaluronan. This receptor:ligand interaction plays an essential role in a number of physiological events including tumour progression, lymphocyte homing into inflammatory sites and tissue morphogenesis during development. In previous studies we have shown that serine phosphorylation is a critical control mechanism for CD44-dependent cell migration. Here we have investigated the target phosphorylation residues by mutating them individually or in combination. These studies demonstrate that Ser325 is the principle CD44 phosphorylation site and that mutation of this residue blocks CD44-mediated cell migration but not hyaluronan binding. In addition, we show that an upstream Ser323 residue is required as part of the kinase consensus site. To further characterize the role of CD44 phosphorylation, phosphorylated and non-phosphorylated peptides spanning the Ser325 region were synthesised and linked to a 16 amino acid Penetratin sequence to mediate efficient plasma membrane translocation. Peptides containing a phosphoserine at residue 325 are efficient blockers of CD44-mediated cell migration but do not reduce CD44 expression or its ability to bind hyaluronan. These data strongly argue that CD44 adhesion and migration are regulated by distinct mechanisms and that migration requires the specific interaction of intracellular component(s) with phosphorylated CD44 receptors.
Initiation of skin basement membrane formation at the epidermo-dermal interface involves assembly of laminins through binding to cell membrane receptors
Authors: Fleischmajer Raul , Utani Atsushi , MacDonald E. Douglas , Perlish Jerome S. , Pan Te-Cheng , Chu Mon-Li , Nomizu Motoyoshi , Ninomiya Yoshifumi , Yamada Yoshihiko 
Published: April 2021

ABSTRACT
To study the mechanism of basement membrane formation, we determined by immunochemistry temporal and spatial expression of laminin-5 (Ln-5), laminin-1 (Ln-1) and their integrin receptors during early skin morphogenesis. A 3-dimensional skin culture was used that allows the study of the sequential molecular events of basement membrane formation at the epidermodermal interface. During early anchorage of keratinocytes to the extracellular matrix there is expression of Ln-5, BP-230 antigen and α3, β1 integrin subunits. During epidermal stratification and prior to the formation of the lamina densa there is assembly of Ln-5, Ln-1, collagen IV and nidogen accompanied by keratinocyte basal clustering of α2, α3, α6, β1, and β4 integrin subunits. The assembly pattern of Ln-1 and Ln-5 can be disturbed with functional antibodies against the β1 (AIIB2) and α6 (GoH3) integrin subunits. Ln-1 assembly can also be disturbed with antibodies against its E8 domain and by competitive inhibition with a synthetic peptide (AG-73) derived from its G-4 domain. Quantitative RT-PCR showed that the dermis contributes about 80% of the laminin γ1 chain mRNA while 20% is produced by the epidermis which emphasizes its dual tissue origin and the major contribution of the mesenchyma in laminin production. The laminin γ2 chain mRNA, present in Ln-5, was mostly of epidermal origin. This study presents evidence that during the initiation of basement membrane formation, laminins bind to keratinocyte plasma membrane receptors and thus may serve as nucleation sites for further polymerization of these compounds by a self-assembly process.
Dis1/TOG universal microtubule adaptors - one MAP for all?
Authors: Ohkura Hiroyuki , Garcia Miguel A. , Toda Takashi 
Published: April 2021

Microtubules play central roles in various cellular processes in eukaryotes. The dynamics and organisation of interphase microtubules and mitotic spindles are dramatically altered during the cell cycle and development. However, the molecular mechanisms underlying this dynamic behaviour remain to be understood. In recent years, a novel family of microtubule-associated proteins (MAPs), the Dis1/TOG family, has emerged as a versatile regulator of microtubule function. These MAPs are highly conserved in eukaryotes from yeasts and plants to humans. The localisation and function of these MAPs are not determined simply by their intrinsic microtubule-binding activity. Instead this family executes its diverse roles by interacting with other regulatory molecules, including microtubule motors and centrosomal proteins. The modular structure of these MAPs may allow them to interact with multiple proteins and thereby be involved in a wide variety of microtubule and spindle functions.
Movies available on-line
FENS-1 and DFCP1 are FYVE domain-containing proteins with distinct functions in the endosomal and Golgi compartments
Authors: Ridley S. H. , Ktistakis N. , Davidson K. , Anderson K. E. , Manifava M. , Ellson C. D. , Lipp P. , Bootman M. , Coadwell J. , Nazarian A. , Erdjument-Bromage H. , Tempst P. , Cooper M. A. , Thuring J. W. J. F. , Lim Z.-Y. , Holmes A. B. , Stephens L. R. , Hawkins P. T. 
Published: April 2021

FENS-1 and DFCP1 are recently discovered proteins containing one or two FYVE-domains respectively. We show that the FYVE domains in these proteins can bind PtdIns3P in vitro with high specificity over other phosphoinositides. Exogenously expressed FENS-1 localises to early endosomes: this localisation requires an intact FYVE domain and is sensitive to wortmannin inhibition. The isolated FYVE domain of FENS-1 also localises to endosomes. These results are consistent with current models of FYVE-domain function in this cellular compartment. By contrast, exogenously expressed DFCP1 displays a predominantly Golgi, endoplasmic reticulum (ER) and vesicular distribution with little or no overlap with FENS-1 or other endosomal markers. Overexpression of DFCP1 was found to cause dispersal of the Golgi compartment defined by giantin and gpp130-staining. Disruption of the FYVE domains of DFCP1 causes a shift to more condensed and compact Golgi structures and overexpression of this mutant was found to confer significant protection to the Golgi against brefeldin-induced dispersal. These properties of DFCP1 are surprising, and suggest FYVE domain-localisation and function may not be exclusively endosomal.Movies available on-line