bluuebunny/crossref_metadata_2025 huggingface dataset:
Fourier transformed spectral bio‐imaging for studying the intracellular fate of liposomes
Authors: Huth Ulrich , Wieschollek Ansgar , Garini Yuval , Schubert Rolf , Peschka‐Süss Regine
Published: December 2003

Background

To improve the efficiency of liposomal drug targeting systems, it is necessary to understand the mechanism of liposome uptake by the cell and to follow the intracellular fate of internalized liposomes and their contents.

Methods

We applied multiple‐color fluorescence imaging spectroscopy, using a combination of five fluorescent dyes with a significant spectral overlap. pH‐sensitive liposomes were labeled with the hydrophilic dye fluorescein isothiocyanate‐dextran (FITC‐dextran) or the lipophilic membrane marker rhodamine‐B‐phosphoethanolamine (Rh‐PE) and incubated with COS‐7 cells. Further, the cells were stained with specific markers: the cell membrane was fluorescently labeled with Vybrant DiO, lysosomes were stained with LysoTracker Red, and 4′,6 diamidino‐2‐phenylindole dihydrochloride was used for counterstaining the nucleus.

Results

All five dyes were used simultaneously and were spectrally distinguished by the system. FITC‐dextran‐labeled liposomes showed a distribution pattern different from identically composed liposomes labeled with Rh‐PE: the highly lipophilic Rh‐PE was colocalized with the lysosomotropic dye LysoTracker Red, whereas liposomal FITC‐dextran was not accompanied by LysoTracker Red in all cases.

Conclusions

(a) Spectral (bio‐) imaging is a powerful method for studying the intracellular fate of liposomal compounds. (b) We assume that the liposome membrane marker Rh‐PE influences the uptake of particles due to its surface‐modifying properties. We propose that this head‐group‐labeled phospholipid acts as a ligand for cellular receptors and triggers receptor‐mediated (clathrin‐dependent) endocytosis. Cytometry Part A 57A:10–21, 2004. © 2003 Wiley‐Liss, Inc.
Direct neural network application for automated cell recognition
Authors: Zheng Qing , Milthorpe Bruce K. , Jones Allan S.
Published: December 2003

Background

Automated cell recognition from histologic images is a very complex task. Traditionally, the image is segmented by some methods chosen to suit the image type, the objects are measured, and then a classifier is used to determine cell type from the object's measurements. Different classifiers have been used with reasonable success, including neural networks working with data from morphometric analysis.

Methods

Image data of cells were input directly into neural networks to determine the feasibility of direct classification by using pixel intensity information. Several types of neural network and their ability to work with cells in a complex patterned background were assessed for a variety of images and cell types and for the accuracy of classification.

Results

Inflammatory cells from animal biomaterial implants in rabbit paravertebral muscle were imaged in histologic sections. Simple, three‐layer, fully connected, back‐propagation neural networks and four‐layer networks with two layers of a shared‐weights neural network were most successful at classifying the cells from the images, with 97% and 98% correct recognition rates, respectively.

Conclusions

The high accuracy recognition rate shows the potential for direct classification of visual image pixel data by neural networks. Cytometry Part A 57A:1–9, 2004. © 2003 Wiley‐Liss, Inc.
Image analysis for automatic segmentation of cytoplasms and classification of Rac1 activation
Authors: Lindblad Joakim , Wählby Carolina , Bengtsson Ewert , Zaltsman Alla
Published: December 2003

Background

Rac1 is a GTP‐binding molecule involved in a wide range of cellular processes. Using digital image analysis, agonist‐induced translocation of green fluorescent protein (GFP) Rac1 to the cellular membrane can be estimated quantitatively for individual cells.

Methods

A fully automatic image analysis method for cell segmentation, feature extraction, and classification of cells according to their activation, i.e., GFP‐Rac1 translocation and ruffle formation at stimuli, is described. Based on training data produced by visual annotation of four image series, a statistical classifier was created.

Results

The results of the automatic classification were compared with results from visual inspection of the same time sequences. The automatic classification differed from the visual classification at about the same level as visual classifications performed by two different skilled professionals differed from each other. Classification of a second image set, consisting of seven image series with different concentrations of agonist, showed that the classifier could detect an increased proportion of activated cells at increased agonist concentration.

Conclusions

Intracellular activities, such as ruffle formation, can be quantified by fully automatic image analysis, with an accuracy comparable to that achieved by visual inspection. This analysis can be done at a speed of hundreds of cells per second and without the subjectivity introduced by manual judgments. Cytometry Part A 57A:22–33, 2004. © 2003 Wiley‐Liss, Inc.
Cytokine upregulation of surface antigens correlates to the priming of the neutrophil oxidative burst response
Authors: Wittmann S. , Rothe G. , Schmitz G. , Fröhlich D.
Published: December 2003

Background

Neutrophil activation is strongly related to organ dysfunction that occurs during systemic inflammatory responses. The aim of our study was to analyze the oxidative burst response in correlation to the up‐ and downregulation of N‐formyl‐L‐methionyl‐L‐leucyl‐phenylalanine (fMLP) receptors and the surface antigens CD11b, CD62L, and CD66b as potential surrogate markers of the degree of neutrophil priming for an increased oxidative burst response induced by proinflammatory cytokines.

Methods

Blood was taken from healthy donors. Neutrophils were pretreated with cytokines (interleukin [IL]–1β, IL‐6, IL‐8, granulocyte‐macrophage colony‐stimulating factor [GM‐CSF], and tumor necrosis factor α [TNFα]; 0.01–10 ng/ml) and stimulated with fMLP (100 nM) in vitro. Functional and phenotypical parameters were quantified flow cytometrically.

Results

The oxidative burst response increased after priming with 0.1 ng/ml TNFα, 1 ng/ml GM‐CSF, or 10 ng/ml IL‐8. Upregulation of fMLP receptors, CD11b, and CD66b and downregulation of CD62L showed a close correlation to the oxidative burst response. Altered expression of these parameters partly reached significance at lower cytokine concentrations in comparison with the oxidative burst. IL‐1β and IL‐6 had no effect.

Conclusions

Our results showed that the expression of phenotypical parameters closely correlates with functional parameters in human neutrophils. Thus an up‐ or downregulation of antigens such as CD11b or CD62L reflects cytokine‐induced functional changes. Cytometry Part A 57A:53–62, 2004. © 2003 Wiley‐Liss, Inc.
Discrimination of the Hoechst side population in mouse bone marrow with violet and near‐ultraviolet laser diodes
Authors: Telford William G. , Frolova Ella G.
Published: December 2003

Background

Discrimination of stem cells with flow cytometric analysis of Hoechst 33342 efflux by the ABCG2 transporter (termed the Hoechst side population, or SP technique) is a valuable methodology for identifying bone marrow progenitors enriched with stem cells. Unfortunately, it requires a ultraviolet (UV) laser source, usually necessitating an expensive and maintenance‐intensive argon‐ or krypton‐ion gas laser on a large‐scale cell sorter. In this study, we evaluated the ability of recently available violet and near‐UV laser diodes to discriminate Hoechst SP on smaller cuvette‐based flow cytometers.

Methods

Violet laser diodes (emitting at 408 and 401 nm) and a near‐UV laser diode (emitting at 370 nm) were mounted on a BD Biosciences LSR II and evaluated for their ability to discriminate Hoechst SP in murine bone marrow.

Results

The violet laser diodes discriminated the Hoechst SP, but with poorer resolution than with the standard UV gas laser on a large‐scale cell sorter. The near‐UV laser diode, in contrast, gave excellent Hoechst SP resolution.

Conclusions

These evaluations indicated that near‐UV laser diodes give excellent Hoechst SP resolution on cuvette‐based instruments. As the next generation of cell sorters integrate cuvette‐based cell interrogation into conventional jet‐in‐air cell separation, these laser sources should become applicable for analysis and physical separation of Hoechst SP cells. Cytometry Part A 57A:45–52, 2004. © 2003 Wiley‐Liss, Inc.
Double staining of Plasmodium falciparum nucleic acids with hydroethidine and thiazole orange for cell cycle stage analysis by flow cytometry
Authors: Jouin Helene , Daher Wassim , Khalife Jamal , Ricard Isabelle , Puijalon Odile Mercereau , Capron Monique , Dive Daniel
Published: December 2003

Background

Microarray analyses of stage‐specific gene expression of Plasmodium falciparum require purification of RNAs from highly synchronized cultures. To date, no reliable method to control the quality of synchronization of P. falciparum cultures is available.

Methods

A double‐staining method using hydroethidine and thiazole orange for nucleic acid staining was carried out to compare by flow cytometric analysis the nucleic acid labeling of synchronized P. falciparum in cultures at different time points of the 48‐h intraerythrocytic cycle.

Results

With this method, we determined the quality of culture synchronization in schizont and ring stages. Nucleic acid analysis, based on thiazole orange fluorescence, clearly showed that low levels of schizonts in ring cultures results in a high contamination of ring nucleic acids by schizonts. Conversely, nucleic acids from trophozoite or schizont cultures containing ring stages did not present a significant contamination by ring nucleic acids.

Conclusion

The results demonstrated a very low nucleic acid content in the ring stage when compared with the high nucleic acid content of schizont‐stage parasites. The rapid and reliable flow cytometric strategy using hydroethidine‐ and thiazole orange‐stained parasite nucleic acids allows monitoring of the purity of the preparation, thus greatly improving the quality assessment of parasite cultures, a critical step to study gene expression patterns. Cytometry Part A 57A:34–38, 2004. © 2003 Wiley‐Liss, Inc.
Traf6 is essential for murine tooth cusp morphogenesis
Authors: Ohazama Atsushi , Courtney Jo‐Maree , Tucker Abigail S. , Naito Asuka , Tanaka Sakae , Inoue Jun‐Ichiro , Sharpe Paul T.
Published: December 2003

Ectodermal appendages such as skin, hair, teeth, and sweat glands are affected in patients with hypohidrotic (anhydrotic) ectodermal dysplasia (HED). It has been established that mutations in the tumor necrosis factor (TNF) superfamily of molecules, i.e., ectodysplasin (EDA), EDA receptor (EDAR), and EDAR‐associated death domain (EDARADD; the intracellular adaptor for EDAR), are responsible for several forms of HED in humans and mice. We show here by in situ hybridisation that another TNF family (orphan) receptor, TROY (also known TAJ, TAJ‐α, TRADE, and TNFRSF19), is strongly coexpressed with Edar in the epithelial enamel knot signalling centres that are believe to regulate cuspal morphogenesis during murine tooth development. Traf6 is known to function as an intracellular adaptor protein for Troy and examination of Traf6 mutant mice revealed abnormalities in molar teeth that are similar but more severe than those produced by mutations in Eda signalling molecules. This finding suggests that, in additional to ectodysplasin, another TNF pathway involving Troy/Traf6 is involved in molar tooth cusp formation and identifies an essential role for a Traf in tooth development. Developmental Dynamics 229:131–135, 2004. © 2003 Wiley‐Liss, Inc.
Significance of the cranial neural crest
Authors: Graham Anthony , Begbie Jo , McGonnell Imelda
Published: December 2003

The cranial neural crest has long been viewed as being of particular significance. First, it has been held that the cranial neural crest has a morphogenetic role, acting to coordinate the development of the pharyngeal arches. By contrast, the trunk crest seems to play a more subservient role in terms of embryonic patterning. Second, the cranial crest not only generates neurons, glia, and melanocytes, but additionally forms skeletal derivatives (bones, cartilage, and teeth, as well as smooth muscle and connective tissue), and this potential was thought to be a unique feature of the cranial crest. Recently, however, several studies have suggested that the cranial neural crest may not be so influential in terms of patterning, nor so exceptional in the derivatives that it makes. It is now becoming clear that the morphogenesis of the pharyngeal arches is largely driven by the pharyngeal endoderm. Furthermore, it is now apparent that trunk neural crest cells have skeletal potential. However, it has now been demonstrated that a key role for the cranial neural crest streams is to organise the innervation of the hindbrain by the cranial sensory ganglia. Thus, in the past few years, our views of the significance of the cranial neural crest for head development have been altered. Developmental Dynamics 229:5–13, 2004. © 2003 Wiley‐Liss, Inc.
Turning heads: Development of vertebrate branchiomotor neurons
Authors: Chandrasekhar Anand
Published: December 2003

The cranial motor neurons innervate muscles that control eye, jaw, and facial movements of the vertebrate head and parasympathetic neurons that innervate certain glands and organs. These efferent neurons develop at characteristic locations in the brainstem, and their axons exit the neural tube in well‐defined trajectories to innervate target tissues. This review is focused on a subset of cranial motor neurons called the branchiomotor neurons, which innervate muscles derived from the branchial (pharyngeal) arches. First, the organization of the branchiomotor pathways in zebrafish, chick, and mouse embryos will be compared, and the underlying axon guidance mechanisms will be addressed. Next, the molecular mechanisms that generate branchiomotor neurons and specify their identities will be discussed. Finally, the caudally directed or tangential migration of facial branchiomotor neurons will be examined. Given the advances in the characterization and analysis of vertebrate genomes, we can expect rapid progress in elucidating the cellular and molecular mechanisms underlying the development of these vital neuronal networks. Developmental Dynamics 229:143–161, 2004. © 2003 Wiley‐Liss, Inc.
Signal integration during development: Insights from the Drosophila eye
Authors: Voas Matthew G. , Rebay Ilaria
Published: December 2003

The Drosophila eye is a highly ordered epithelial tissue composed of ∼750 subunits called ommatidia arranged in a reiterated hexagonal pattern. At higher resolution, observation of the constituent photoreceptors, cone cells, and pigment cells of the eye reveals a highly ordered mosaic of amazing regularity. This relatively simple organization belies the repeated requirement for spatially and temporally coordinated inputs from the Hedgehog (Hh), Wingless (Wg), Decapentaplegic (Dpp), JAK‐STAT, Notch, and receptor tyrosine kinase (RTK) signaling pathways. This review will discuss how signaling inputs from the Notch and RTK pathways, superimposed on the developmental history of a cell, facilitate context‐specific and appropriate cell fate specification decisions in the developing fly eye. Lessons learned from investigating the combinatorial signal integration strategies underlying Drosophila eye development will likely reveal cell–cell communication paradigms relevant to many aspects of invertebrate and mammalian development. Developmental Dynamics 229:162–175, 2004. © 2003 Wiley‐Liss, Inc.
Relative expression of Slug, RhoB, and HNK‐1 in the cranial neural crest of the early chicken embryo
Authors: Del Barrio Marta G. , Nieto M. Angela
Published: December 2003

The neural crest constitutes a complex population of cells that originates at the edges of the neural plate of vertebrate embryos and gives rise to a high diversity of tissues and cell types. Molecular markers are very useful to identify cell populations, and in the case of the neural crest at early stages, many of them have been described. Here, we show a series of chicken embryos double labeled for several of the most commonly used crest markers that evidence the existence of different subpopulations. Slug is a very good marker for premigratory and early migratory cranial neural crest, RhoB labels delaminating cells and the very early migratory population, and the HNK‐1 epitope is acquired in the migratory crest cells at a distance from the neural tube, with a significant proportion of the Slug‐expressing migratory cells negative for HNK‐1. The existence of these crest subpopulations should be considered when analyzing both wild‐type embryos and the phenotype of experimentally manipulated chick embryos. Developmental Dynamics 229:136–139, 2004. © 2003 Wiley–Liss, Inc.
Gene regulatory factors in pancreatic development
Authors: Jensen Jan
Published: December 2003

The intensity of research on pancreatic development has increased markedly in the past 5 years, primarily for two reasons: we now know that the insulin‐producing β‐cells normally arise from an endodermally derived, pancreas‐specified precursor cell, and successful transplants of islet cells have been performed, relieving patients with type I diabetes of symptoms for extended periods after transplantation. Combining in vitro β‐cell formation from a pancreatic biopsy of a diabetic patient or from other stem‐cell sources followed by endocrine cell transplantation may be the most beneficial route for a future diabetes therapy. However, to achieve this, a thorough understanding of the genetic components regulating the development of β‐cells is required. The following review discusses our current understanding of the transcription factor networks necessary for pancreatic development and how several genetic interactions coming into play at the earliest stages of endodermal development gradually help to build the pancreatic organ. Developmental Dynamics 229:176–200, 2004. © 2003 Wiley‐Liss, Inc.
MMP‐2 plays an essential role in producing epithelial‐mesenchymal transformations in the avian embryo
Authors: Duong Tuan D. , Erickson Carol A.
Published: December 2003

To investigate the roles that matrix‐degrading proteases may have in development of the chicken embryo, we documented the expression pattern of matrix metalloprotease‐2 (MMP‐2, 72‐kDa type IV collagenase or gelatinase A) and perturbed its function in vitro and in vivo. MMP‐2 is expressed as neural crest cells detach from the neural epithelium during an epithelial‐mesenchymal transformation (EMT) but is rapidly extinguished as they disperse. It is also expressed in the sclerotome and in the dermis at the time that the EMT is initiated, and also as these cells migrate, and is down‐regulated once motility has ceased. These patterns suggest that MMP‐2 plays a role in cell motility during the EMT and during later morphogenesis. Inhibitors of MMPs, including BB‐94 and TIMP‐2 (tissue inhibitor of metalloprotease‐2), prevent the EMT that generates neural crest cells, both in tissue culture and in vivo, but do not affect migration of the cells that have already detached from the neural tube. Similarly, knockdown of MMP‐2 expression in the dorsal neural tube using antisense morpholino oligos perturbs the EMT, but also does not affect migration of neural crest cells after they have detached from the neural tube. On the other hand, when somites in culture are treated with TIMP‐2, some mesenchymal cells are produced, suggesting that they undergo the EMT, but show greatly reduced migration through the collagen gel. MMP‐2 is also expressed in mesenchyme where tissue remodeling is in progress, such as in the developing feather germs, in the head mesenchyme, in the lateral plate mesoderm, and in the limb dermis, especially in the regions where tendons are developing. Comparisons of these expression patterns in multiple embryonic tissues suggest a probable role for MMP‐2 in the migration phase of the EMT, in addition to mesenchyme dispersion and tissue remodeling. Developmental Dynamics 229:42–53, 2004. © 2003 Wiley‐Liss, Inc.
Complementation of melanocyte development in SOX10 mutant neural crest using lineage‐directed gene transfer
Authors: Hou Ling , Loftus Stacie K. , Incao Arturo , Chen Amy , Pavan William J.
Published: December 2003

An in vitro gene complementation approach has been developed to dissect gene function and regulation in neural crest (NC) development and disease. The approach uses the avian RCAS virus to express genes in NC cells derived from transgenic mice expressing the RCAS receptor TVA, under the control of defined promoter elements. Constructs for creating TVA transgenic mice were developed using site‐specific recombination GATEWAY (GW), compatible vectors that can also be used to facilitate analysis of genomic fragments for transcriptional regulatory elements. By using these GW vectors to facilitate cloning, transgenic mouse lines were generated that express TVA in SOX10‐expressing NC stem cells under the control of the Pax3 promoter. The Pax3‐tv‐a transgene was bred onto a Sox10‐deficient background, and the feasibility of complementing genetic NC defects was demonstrated by infecting the Pax3‐tv‐a cells with an RCAS‐Sox10 expression virus, thereby rescuing melanocyte development of Sox10‐deficient NC cells. This system will be useful for assessing genetic hierarchies in NC development. Developmental Dynamics 229:54–62, 2004. © 2003 Wiley‐Liss, Inc.
Homocysteine inhibits cardiac neural crest cell formation and morphogenesis in vivo
Authors: Tierney Brent J. , Ho Trang , Reedy Mark V. , Brauer Philip R.
Published: December 2003

Elevated homocysteine increases the risk of neurocristopathies. Here, we determined whether elevating homocysteine altered the proliferation or number of chick neural crest cells that form between the midotic and third somite in vivo. Homocysteine increased the number of neural tube cells but decreased neural crest cell number. However, the sum total of cells was not different from controls. In controls, the 5‐bromo‐2′‐deoxyuridine‐labeling index was higher in newly formed neural crest cells than in their progenitors, paralleling reports showing these progenitors must pass the restriction point before undergoing epithelial–mesenchymal transition. Homocysteine decreased the labeling index of newly formed neural crest cells, suggesting that it inhibited cell cycle progression of neural crest progenitors or the S‐phase entry of newly formed neural crest cells. Homocysteine also inhibited neural crest dispersal and decreased the distance they migrated from the neural tube. These results show neural crest morphogenesis is directly altered by elevated homocysteine in vivo. Developmental Dynamics 229:63–73, 2004. © 2003 Wiley‐Liss, Inc.
Neural crest and the origin of ectomesenchyme: Neural fold heterogeneity suggests an alternative hypothesis
Authors: Weston James A. , Yoshida Hisahiro , Robinson Victoria , Nishikawa Satomi , T. Fraser Stuart , Nishikawa Shinichi
Published: December 2003

The striking similarity between mesodermally derived fibroblasts and ectomesenchyme cells, which are thought to be derivatives of the neural crest, has long been a source of interest and controversy. In mice, the gene encoding the alpha subunit of the platelet‐derived growth factor receptor (PDGFRα) is expressed both by mesodermally derived mesenchymal cells and by ectomesenchyme. Whole‐mount immunostaining previously revealed that PDGFRα is present in the cephalic neural fold epithelium of early murine embryos (Takakura et al. [1997] J Histochem Cytochem 45:883–893). We now show that, within the neural fold, a sharp boundary exists between E‐cadherin–expressing non‐neural epithelium and the neural epithelium of the dorsal ridge. In addition, we found that cells coexpressing E‐cadherin and PDGFRα are present in the non‐neural epithelium of the neural folds. These observations raise the possibility that at least some PDGFRα+ ectomesenchyme originates from the lateral non‐neural domain of neural fold epithelium. This inference is consistent with previous reports (Nichols [ 1981] J Embryol Exp Morphol 64:105–120; Nichols [ 1986] Am J Anat 176:221–231) that mesenchymal cells emerge precociously from an epithelial neural fold domain resembling the primitive streak in the early embryonic epiblast. Therefore, we propose the name “metablast” for this non‐neural epithelial domain to indicate that it is the site of a delayed local delamination of mesenchyme similar to involution of mesoderm during gastrulation. We further propose the testable hypothesis that neural crest and ectomesenchyme are developmentally distinct progenitor populations and that at least some ectomesenchyme is metablast‐derived rather than neural crest‐derived tissue. Developmental Dynamics 229:118–130, 2004. © 2003 Wiley‐Liss, Inc.
T‐box genes in early embryogenesis
Authors: Showell Chris , Binder Olav , Conlon Frank L.
Published: December 2003

The T‐box gene family, encoding related DNA‐binding transcriptional regulators, plays an essential role in controlling many aspects of embryogenesis in a wide variety of organisms. The T‐box genes exhibit diverse patterns of spatial and temporal expression in the developing embryo, and both genetic and molecular embryological studies have demonstrated their importance in regulating cell fate decisions that establish the early body plan, and in later processes underlying organogenesis. Despite these studies, little is known of either the regulation of the T‐box genes or the identities of their transcriptional targets. The aim of this review is to examine the diverse yet conserved roles of several T‐box genes in regulating early patterning in chordates and to discuss possible mechanisms through which this functional diversity might arise. Developmental Dynamics 229:201–218, 2004. © 2003 Wiley‐Liss, Inc.
Comparative analysis of neural crest cell death, migration, and function during vertebrate embryogenesis
Authors: Kulesa Paul , Ellies Debra L. , Trainor Paul A.
Published: December 2003

Cranial neural crest cells are a multipotent, migratory population that generates most of the cartilage, bone, connective tissue and peripheral nervous system in the vertebrate head. Proper neural crest cell patterning is essential for normal craniofacial morphogenesis and is highly conserved among vertebrates. Neural crest cell patterning is intimately connected to the early segmentation of the neural tube, such that neural crest cells migrate in discrete segregated streams. Recent advances in live embryo imaging have begun to reveal the complex behaviour of neural crest cells which involve intricate cell‐cell and cell‐environment interactions. Despite the overall similarity in neural crest cell migration between distinct vertebrates species there are important mechanistic differences. Apoptosis for example, is important for neural crest cell patterning in chick embryos but not in mouse, frog or fish embryos. In this paper we highlight the potential evolutionary significance of such interspecies differences in jaw development and evolution. Developmental Dynamics 229:14–29, 2004. © 2003 Wiley‐Liss, Inc.
Identification of neural crest competence territory: Role of Wnt signaling
Authors: Bastidas Francisco , De Calisto Jaime , Mayor Roberto
Published: December 2003

In recent years, research on neural crest induction has allowed the identification of several molecules as candidates for neural crest inducers. Although many of these molecules have the ability to induce neural crest in different assays, a general mechanism of neural crest induction that includes a description of the tissues that produce the inductive signals and the time and steps in which this process takes place remains elusive. To better understand the mechanism of neural crest induction, we developed an assay that has been used previously by Nieuwkoop to study anterior–posterior pattern of the neural plate. Folds of competent ectoderm were implanted in different positions of a young neurula embryo, and the induction of neural crest was analyzed using the expression of the neural crest marker Xslug. We identified a very localized region of the early neurula where it is possible to get neural crest induction, whereas all of the regions tested showed a clear induction of the neural plate marker Xsox2. These results indicate that there is a region in the embryo with the appropriate combination of signals needed to induce neural crest cells; we called this region the neural crest competence territory. In addition, our results show that neural crest induction is always accompanied by neural plate induction, but there are many cases where neural plate was induced without neural crest. These results support the model in which the neural crest is induced by an interaction between neural plate and epidermis, but they also suggest that additional signals are required. By making grafts of different sizes and implanting them in the epidermis or the neural plate, we concluded that one of the inductive signals is produced in the dorsal region of the embryo and travels into the ectoderm. Finally, by performing gain‐ and loss‐of‐function of Wnt signaling experiments, we show that this pathway plays an important role not only in neural crest induction but also in the specification of the neural crest competence territory. Developmental Dynamics 229:109–117, 2004. © 2003 Wiley‐Liss, Inc.
Slow degeneration of zebrafish Rohon‐Beard neurons during programmed cell death
Authors: Reyes Rosario , Haendel Melissa , Grant Deanna , Melancon Ellie , Eisen Judith S.
Published: December 2003

Rohon‐Beard cells are large, mechanosensory neurons located in the dorsal spinal cord of anamniote vertebrates. In most species studied to date, these cells die during development. We followed labeled Rohon‐Beard cells in living zebrafish embryos and found that they degenerate slowly, over many days. During degeneration, the soma shrinks and finally disappears, and the processes become beady in appearance and finally break apart, but they do not retract. Zebrafish Rohon‐Beard cells apparently fragment their DNA, as revealed by terminal deoxynucleotidyl transferase‐mediated dUTP nick end‐labeling (TUNEL) labeling, before undergoing degenerative morphologic changes. We also followed the development of labeled dorsal root ganglion neurons, as they are developing at the same stages that Rohon‐Beard cells are degenerating. We found that, although axons of both cell types extend into similar regions, Rohon‐Beard cells degenerate normally in mutants lacking dorsal root ganglia, providing evidence that interactions between the two cell types are not responsible for Rohon‐Beard cell degeneration. Developmental Dynamics 229:30–41,2004. © 2003 Wiley‐Liss, Inc.
Long‐distance cue from emerging dermis stimulates neural crest melanoblast migration
Authors: Tosney Kathryn W.
Published: December 2003

Neural crest melanoblasts display unique navigational abilities enabling them to colonize the dorsal path between ectoderm and somite. One signal shown here to elicit melanoblast migration is a chemotactic cue supplied by the emerging dermis. Until dermis emerges, melanoblasts fail to enter the dorsal path. The dermis emerges from a site that is too distant to stimulate migration by cell contact. Instead, surgeries show that dermis elicits migration from a distance. When dermis is grafted distally, neural crest cells enter the path precociously. Moreover, large grafts recruit melanoblasts from the control sides (without increasing crest cell numbers) as well as a few crest cells from ventral somite. Because other grafted tissues fail to stimulate migration, the dermis stimulus is specific. This report is the first documentation that trunk neural crest cells can be guided chemotactically. It also extends evidence that migration is exquisitely sensitive to temporal–spatial patterns of somite morphogenesis. Developmental Dynamics 229:99–108, 2004. © 2003 Wiley‐Liss, Inc.
Skeletal and pigment cell defects in the lockjaw mutant reveal multiple roles for zebrafish tfap2a in neural crest development
Authors: Knight Robert D. , Javidan Yashar , Nelson Sarah , Zhang Tailin , Schilling Thomas
Published: December 2003

Members of the AP‐2 transcription factor family have critical roles in many aspects of embryonic development. The zebrafish tfap2a mutant lockjaw (low) displays defects in skeletal and pigment cell derivatives of the neural crest. Here we show essential roles for tfap2a in subsets of embryonic cartilages and pigment cells. Defects in cartilage of the hyoid arch in low correlate with a loss of Hox group 2 gene expression and are suggestive of a transformation to a mandibular fate. In contrast, loss of joints in the mandibular arch and defects in certain types of pigment cells suggest a requirement for tfap2a independent of Hox regulation. Early melanophores do not develop in low mutants, and we propose that this results in part from a loss of kit function, leading to defects in migration, as well as kit‐independent defects in melanophore specification. Iridophores are also reduced in low, in contrast to xanthophores, revealing a role for tfap2a in the development of pigment subpopulations. We propose a model of tfap2a function in the neural crest in which there are independent functions for tfap2a in specification of subpopulations of pigment cells and segmental patterning of the pharyngeal skeleton through the regulation of Hox genes. Developmental Dynamics 229:87–98, 2004. © 2003 Wiley‐Liss, Inc.
Multiple roles of Sox2, an HMG‐box transcription factor in avian neural crest development
Authors: Wakamatsu Yoshio , Endo Yukinori , Osumi Noriko , Weston James A.
Published: December 2003

Expression of Sox2, which encodes an HMG‐box–type transcription factor, is down‐regulated in the neural plate when neural crest segregates from dorsal neural tube and remains low during crest cell migration. Sox2 expression is subsequently up‐regulated in some crest‐derived cells in the developing peripheral nervous system and is later restricted to glial sublineages. Misexpression of Sox2 and mutant forms of Sox2 both in neural plate explants and in embryonic ectoderm reveals that Sox2 inhibits neural crest formation as a transcriptional activator. Similar manipulation of Sox2 function in migratory and postmigratory neural crest‐derived cells indicates that Sox2 regulates proliferation and differentiation in developing peripheral nervous system. Developmental Dynamics 229:74–86, 2004. © 2003 Wiley‐Liss, Inc.
Weathering and biokarst development on marine terraces, northwest Morocco
Authors: Duane Michael J. , AL‐Mishwat Ali T. , Rafique Mohammed
Published: December 2003

Weathering features are described from an arid coastal area in northern Morocco which are indicative of invasive chasmolithic and endolithic microbial communities. Active weathering of marine terraces and karst development is associated with endolithic and epilithic algae responsible for boring, disintegration of matrix and mineral fabrics, solution and biomineralization that undermines the marine carbonate platform. Evidence of a range of biological weathering agents remains preserved, speciﬁcally calciﬁed ﬁlaments and sporangial material. An abundance of ﬁlaments and spores representative of a consortium of algae, fungi, cyanobacteria and lichens is associated with the most denuded outcrops. The array of microbes contributes to the formation of the stromatolites to depths of 0·5 m within the limestone substrate. The preservation of stromatolites is supported by calciﬁcation of spores and ﬁlaments, with trapping and binding of carbonate held in suspension by vadose waters. The pervasive weathering on this sector of coastline has important practical implications for coastal planning and development authorities in Morocco. Copyright © 2003 John Wiley & Sons, Ltd.
Processes of tidal channel development in salt and freshwater marshes
Authors: Perillo Gerardo M. E. , Iribarne Oscar O.
Published: December 2003

Mechanisms for the formation of creeks in tidal ﬂats are rarely discussed in literature. There are some general theories about their formation but there are no data to support the evidence. It is generally believed that marshes inherit creeks from previous tidal ﬂats that their plants colonize and further modify them. The aim of this paper is to present three mutually exclusive cases from marshes in Argentina where creeks are formed by either purely physical or biological–physical interactions. Except for Loyola Bay, this is the ﬁrst discussion of these mechanisms. They may represent special cases, but the fact that all three of them occur along the coast of Argentina, could indicate that similar cases may be found somewhere else. Copyright © 2003 John Wiley & Sons, Ltd.
Surface particle sizes on armoured gravel streambeds: effects of supply and hydraulics
Authors: Whiting Peter J. , King John G.
Published: December 2003

Most gravel‐bed streams exhibit a surface armour in which the median grain size of the surface particles is coarser than that of the subsurface particles. This armour has been interpreted to result when the supply of sediment is less than the ability of the stream to move sediment. While there may be certain sizes in the bed for which the supply is less than the ability of the stream to transport these sizes, for other sizes of particles the supply may match or even exceed the ability of the channel to transport these particles. These sizes of particles are called ‘supply‐limited’ and ‘hydraulically limited’ in their transport, respectively, and can be differentiated in dimensionless sediment transport rating curves by size fractions. The supply‐ and hydraulically limited sizes can be distinguished also by comparing the size of particles of the surface and subsurface. Those sizes that are supply‐limited are winnowed from the bed and are under‐represented in the surface layer. Progressive truncation of the surface and subsurface size distributions from the ﬁne end and recalculation until the size distributions are similar (collapse), establishes the break between supply‐ and hydraulically limited sizes. At sites along 12 streams in Idaho ranging in drainage area from about 100 to 4900 km2, sediment transport rating curves by size class and surface and subsurface size distributions were examined. The break between sizes that were supply‐ and hydraulically limited as determined by examination of the transport rate and surface and subsurface size distributions was similar. The collapse size as described by its percentile in the cumulative size distribution averaged D36 of the surface and D73 of the subsurface. The discharge at which the collapse size began to move averaged 88 per cent of bankfull discharge. The collapse size decreased as bed load yield increased and increased with the degree of selective transport. Copyright © 2003 John Wiley & Sons, Ltd.
The influence of parent material on topsoil geochemistry in eastern England
Authors: Rawlins B. G. , Webster R. , Lister T. R.
Published: December 2003

The topsoil of around 10 000 km2 in eastern England has recently been sampled intensely at 4609 sites to characterize its geochemistry. The parent materials, which include both solid geology and Quaternary sediments, range in age from Permian to Holocene. The distributions of the concentrations of major and trace elements have been characterized geostatistically, and the role of parent material on their spatial structure (anisotropy) and their spatial relationships (coregionalization) have been investigated.

Analysis of variance with the sites grouped by major parent material type showed that this classiﬁcation accounted for 14 to 48 per cent of the variance for the various elements. Global variograms of 13 elements (Al, As, Ca, Cr, Cu, Fe, Mg, Mo, Ni, P, Pb, Ti, and U) have been computed and modelled. Eleven of the variograms seem to comprise two structures, both of which we modelled with spherical functions, one of short range, 3·5 to 9 km, and the other with a range of 15 to 23 km. The models included a nugget variance, which varied from 27 per cent (for As, Fe, and Mg) to 63 per cent (for P) of the total. The long‐range structures are related to the separations of the major parent materials.

The variograms of several elements showed appreciable anisotropy, most notably that of Mg. Anisotropy is evident at short ranges of less than 5 km. This accords with the geological structure of the beds which dip from west to east so that their outcrops are elongated from north to south. A linear model of coregionalization ﬁtted to the data emphasized several important geochemical associations, which we interpret. Elements commonly associated with clay minerals (Mg, Al) and the clay size fraction (Ti) are dominated by the long‐range structure of the coregionalization, whilst several trace elements (As, Cr, Ni and U) are spatially correlated with Fe over short distances, through adsorption of the former on the surfaces of Fe oxyhydroxides.

The topsoil around large urban areas is enriched in lead, but it is not clear whether anthropogenic sources are responsible for this metal's anomalous spatial relationships with other elements. Crown copyright © 2003. Reproduced with the permission of Her Majesty's Stationery Ofﬁce. Published by John Wiley & Sons, Ltd.
Sphenopteris coemansiAndrae – neue, aussagefähige Funde
Authors: Daber R.
Published: December 2003

Im Ergebnis paläobotanischer Geländearbeit im Saarbecken wurden zwei Stücke von Sphenopteris coemansi Andrae entdeckt, die nunmehr Spheno‐pteris coemansi und Sphenopteris lanceolata besser vergleichen lassen. Diese beiden nahestehenden Arten unterscheiden sich in der Form und in der Anzahl der Blättchen (der Fiedern letzter Ordnung) im Wedel, was meine Abbildungen dokumentieren. Wenn jemand über Sphenopteris coemansi Genaueres erfahren möchte, so sollte er die Abbildung, die Andrae 1865 veröffentlichte, und ergänzend dazu diese beiden im Saarbecken gemachten Funde betrachten.
Notes on South American Valerianaceae I
Authors: Weberling F.
Published: December 2003

A new species of Belonanthus, Belonanthus theodorici sp. nova, is described. It is characterized by spathulate foliage leaves, the ovate blades of which are rather distinctly contracted into a long and narrow sheathing petiole and bear a dense covering with long hairs, giving the surface of the rosette a silvery sheen. In the monothyrsoid inflorescence the peduncles (hypopodia) of the lower partial inflorescences are considerably elongated. – Valeriana micropterina Wedd., V. poterioides Graebn., V. thalictroides Graebn. and V. aspleniifolia Killip are included into Valeriana microptera. – For Valeriana fonkii Phil. and V. radicalis Clos reliable distinctive characters are named. – For Valeriana decussata Ruiz & Pav. virescent calices with green sepals are described and illustrated.
Vergleichende Untersuchungen zur Sprossvariation bei PlectranthusL'Herit. (Lamiaceae)
Authors: Pohlheim F.
Published: December 2003

Drei Periklinalchimären von Plectranthus forsteri Benth. wurden analysiert. Typ 1 und Typ 2 sind Trichimären. Typ 3 ist eine Monektochimäre. Konstitutionen in L1, L2, L3: Typ 1: weiß/normalwüchsig – hellgrün/normalwüchsig – grün/normalwüchsig; Typ 2: weiß/normalwüchsig – weiß/wachstumsgehemmt – grün/normalwüchsig, Typ 3: weiß/normalwüchsig – grün/normalwüchsig – grün/normalwüchsig. Es wird gezeigt, dass perikline Teilungen in sich entwickelnden Epidermen gehäuft auftreten, wenn L1 von einer wachstumsgehemmten L2‐Komponente unterlagert ist.
On the occurrence of non‐axillary ovules in Tetraclinis articulata (Vahl) Mast. (Cupressaceae s.str.)
Authors: Jagel A. , Stützel Th.
Published: December 2003

The cone morphology in Tetraclinis was studied to elucidate the taxonomic position of the genus. A careful analysis of the cone development shows that the characters used as arguments for an affiliation within Callitroideae are superficial and of little taxonomic significance. The developmental patterns indicate a position of Tetraclinis within Cupressoideae. Tetraclinis displays ovules inserted directly at the distal end of the cone axis and not born in the axil of a seed scale as recently shown for Juniperus (Schulz et al. 2003) and Microbiota (Jagel & Stützel 2001b). The close relationship between Tetraclinis, Juniperus and Cupressus as suggested by Saxton (1913) based on embryological data, by Gadek & Quinn (1985) based on biflavones and by Gadek et al. (2000) based on DNS‐sequences is supported by the morphological data presented here. Conflicting morphological concepts or morphological trees (e.g. Gadek et al. 2000) are in parts weakly supported and suffer either from ambiguous coding of morphological data or are based on historical morphological errors. To calculate reliable morphological trees, however, requires data of similar quality and cannot be achieved by using data which are tailed to the use in effective diagnostic keys.
The distribution of the vegetation in the Uvs‐nuur basin and its surrounding mountain ranges
Authors: Hilbig W.
Published: December 2003

The paper informs on the distribution and the ecological and altitudinal conditions of the plant communities which characterize the vegetation in the Uvs‐nuur basin and the surrounding mountain ranges. This is shown by means of three vegetation profiles extending from North to South in the western, middle and eastern part of the territory belonging to the Uvs Aymak (Mongolia) and – in the North – to the Republic of Tuva (Russian Federation).

The manifold vegetation is represented in the center of the basin at 760 m above sea level by water, reed, salt, and meadow communities. The semi desert vegetation (800–1000 m) turns to steppe vegetation (900–1400 m), which occurs from the inner part of the basin till the sand areas in the East and the foothills of the mountain ranges. Plant communities of the ruderal and weed vegetation can be met in the settlements and on arable fields. Larch forests together with meadow steppes characterize the landscape from 1600 till 2300 m, the first predominant in northern, the latter in southern exposition. The alpine belt above 2300 m is represented by stands of Dryas oxyodonta and alpine Kobresia meadows, which are followed from 2600 m by high alpine cushion vegetation.
Stability and slightly supercritical oscillatory regimes of natural convection in a 8:1 cavity: solution of the benchmark problem by a global Galerkin method
Authors: Gelfgat Alexander Yu.
Published: December 2003

The global Galerkin method is applied to the benchmark problem that considers an oscillatory regime of convection of air in a tall two‐dimensional rectangular cavity. The three most unstable modes of the linearized system of the Boussinesq equations are studied. The converged values of the critical Rayleigh numbers together with the corresponding oscillation frequencies are calculated for each mode. The oscillatory flow regimes corresponding to each of the three modes are approximated asymptotically. No direct time integration is applied. Good agreement with the previously published results obtained by solution of the time‐dependent Boussinesq equations is reported. Copyright © 2004 John Wiley & Sons, Ltd.
Wenn kleine Organismen große Wirkung zeigen
Authors: Lange Otto L.
Published: December 2003

In allen warmen und kalten Trockengebieten der Erde gibt es lebende Bodenkrusten. Sie bilden nicht nur bemerkenswert ausdauernde Lebensgemeinschaften, sondern schützen den Boden effektiv vor Erosion durch Wind oder Wasser
Der Rhesusaffe und die Vermehrungsstrategie
Authors: Schmidtke Jörg , Nürnberg Peter , Krawczak Michael
Published: December 2003

Das Rhesusaffenmännchen verlässt seine Geburtsgruppe, um sich fortzupflanzen. Auf der „Affeninsel”︁ Cayo Santiago bei Puerto Rico machten sich Forscher auf die Suche nach dem Gen, das das Wanderverhalten von Primaten steuert
Der Griff in die Computerwelt
Authors: Schmidt Günther
Published: December 2003

Bei Computerspielen oder anderen multimedialen Anwendungen erhält der Nutzer ausschließlich visuelle und akustische Sinneseindrücke. Neuartige Tastdisplays helfen, auch Berührungsreize zu vermitteln, was die Grundlage für ein wirklichkeitsnahes „Begreifen”︁ am Computer legt