Pattern regulation along the proximodistal axis of the developing chick limb

Transplants creating presumptively excess or deficient proximodistal segments were performed to investigate pattern regulation in stage 21 and stage 23 chick limb buds. Excess skeletal elements were not removed by regulation. Deficiencies appeared to be regulated by host tissue. The ability of the host tissue to participate in regulation declined in more proximal tissue and with increased age. These results suggest that there are two requirements for pattern regulation. First, the tissue in question must be sufficiently close to the ectodermal ridge before it can respond. Results of previous work and implications for pattern formation are discussed with these requirements in mind.     

Electrical properties of the body wall of Hydra

If the hydrostatic pressure in the enteron of Hydra is made more than 2–4 mm of water greater than the outside pressure, the animal becomes distended, indicating that the normal enteron pressure is less than this. Positive enteron pressure attenuates the spontaneous, negative-going electrical spikes across the body wall, which are called contraction pulses (CP''s) because of their relation to column contraction. Pressure has little effect on the transepithelial resting potential. The low frequency electrical impedance of the column is nonlinear. The impedance tends to increase as the transepithelial potential is made more negative. The nonlinearity has both initial and delayed components. The DC impedance of the column near the resting potential averages 100 kohms (approximately 5 kohms-cm²). The phase between transepithelial potential and imposed sinusoidal current approaches -90° with increasing current frequency. Bode plots of the column impedance and the phase lag indicate that the column has three or more time constants. CP''s show several unusual features: (a) their amplitude and frequency are essentially independent of the transepithelial potential when the latter is altered by imposed current; (b) there is practically no change in column impedance during CP firing; (c) when the transepithelial potential is clamped at zero, CP''s continue to appear spontaneously as current spikes. These features are consistent with the hypothesis that the CP-generating membrane forms but a small fraction of the total transverse impedance of the column.     

Polyamine anabolic/catabolic regulation along the woody grapevine plant axis

The distribution of the endogenous PA fractions throughout the entire perennial woody grapevine (Vitis vinifera L.) plant was studied, along with the expression profiles of the PA anabolic and catabolic genes and their substrates and secondary metabolites. Putrescine fractions increased with increasing leaf age, although the expression of its biosynthetic enzymes Arg and Orn decarboxylases decreased. Orn transport from young organs dramatically enhanced putrescine biosynthesis in older tissues, via the Orn decarboxylase pathway. S-adenosylmethionine decarboxylase and spermidine synthase genes were down-regulated during development in a tissue/organ-specific manner, as were spermidine and spermine levels. In contrast, amine oxidases, peroxidases and phenolics increased from the youngest to the fully developed vascular tissues; they also increased from the peripheral regions of leaves to the petioles. Hydrogen peroxide generated by amine oxidases accumulated for the covalent linkage of proteins via peroxidases during lignification. These results could be valuable for addressing further questions on the role of PAs in plant development.     

In the multiheaded strain (mh-1) of Hydra magnipapillata the ectodermal epithelial cells are responsible for the formation of additional heads and the endodermal epithelial cells for the reduced ability to regenerate a foot

Hydra consist of three self-renewing cell lineages: the ectodermal epithelial, endodermal epithelial and interstitial cell lineages. The role of these cell lineages in head formation and foot regeneration in Hydra magnipapillata was studied by comparing the multiheaded strain mh-1 with the wild-type. Adult polyps of this strain show a reduced ability to regenerate a foot in the apical body half several days before additional heads are formed there. Cell lineage chimeras were produced, and it was found that in mh-1, the ectodermal epithelial cell lineage is responsible for the formation of additional heads, whereas the endodermal epithelial cell lineage and, to a lesser extent, the derivatives of the interstitial cell lineage, are responsible for the reduced ability of foot regeneration.     

Draft genome sequence of Shewanella sp. strain HN-41, which produces arsenic-sulfide nanotubes

The dissimilatory metal reducing bacterium Shewanella sp. strain HN-41 was first reported to produce novel photoactive As-S nanotubes via reduction of As(V) and S(2)O(3)(2-) under anaerobic conditions. Here we report the draft genome sequence and annotation of strain HN-41.     

Analysis of a foot regeneration deficient strain of Hydra oligactis.

A foot regeneration deficient strain of Hydra oligactis with altered size regulation was investigated. Analysis of the concentration of four morphogenetically active substances in Hydra oligactis showed that the foot regeneration deficiency was mainly due to a drastically reduced foot activator concentration. Foot activator was distributed as a very steep gradient in Hydra oligactis leading to a more severe impairment of foot regeneration the closer to the head cutting was done. The concentration of foot inhibitor was comparable, that of head activator slightly increased and that of head inhibitor reduced compared to Hydra vulgaris. Studies at the cellular level implied that the enlarged gastric region was due to an elevated level of inhibition hinting at a shift in the ratio between bound and free head inhibitor in this animal.     

MIG-13 positions migrating cells along the anteroposterior body axis of C. elegans.

The C. elegans Q neuroblasts and their descendants migrate along the anteroposterior (A/P) body axis to positions that are not associated with any obvious landmarks. We find that a novel protein, MIG-13, is required to position these cells correctly. MIG-13 is a transmembrane protein whose expression is restricted to the anterior and central body regions by Hox gene activity. MIG-13 functions non-cell autonomously within these regions to promote migration toward the anterior: loss of mig-13 activity shifts the Q descendants toward the posterior, whereas increasing the level of MIG-13 shifts them anteriorly in a dose-dependent manner. Our findings suggest that MIG-13 is a component of a global A/P migration system, and that the level of MIG-13 determines where along the body axis these migrating cells stop.     

Surface properties of regenerating limb cells: Evidence for gradation along the proximodistal axis

Abstract. When two limb regeneration blastemas are cocultured in vitro, proximal blastemas surround distal ones in a position-related hierarchy, whereas blastemas from the same level exhibit no engulfment behavior. Regenerative processes dependent on positional information can be interpreted in terms of differences in surface adhesive properties of limb cells.     

Barrier properties and tight junction protein expression along the longitudinal axis of rat intestine

The tight junction (TJ) protein family of claudins is a major determinant of barrier properties in a wide variety of epithelia. Aim of the study was to compare epithelial barrier properties with the presence of TJ proteins in exactly defined intestinal segments. Transepithelial resistance (R(t)) of duodenum, jejunum, ileum and colon tissue preparations was measured in Ussing chambers. In parallel, expression of TJ proteins was analyzed by Western blots. Colon was characterized by higher R(t) than more proximal segments. However, among the small intestinal segments, R(t) was highest in duodenum and lowest in ileum. Along the intestine different claudins were detected by Western blotting with different signal intensities. Colon showed strongest signals for sealing claudins in accordance with R(t), whereas predominant expression of permeability-mediating claudins was observed in small intestinal segments. Along the intestine, claudins show a marked segment-specific expression which is in accordance with respective barrier properties.     

Structural dynamics and epigenetic modifications of Hoxc loci along the anteroposterior body axis in developing mouse embryos

Hox genes are organized as clusters and specify regional identity along the anteroposterior body axis by sequential expression at a specific time and region during embryogenesis. However, the precise mechanisms underlying the sequential spatio-temporal, collinear expression pattern of Hox genes are not fully understood. Since epigenetic modifications such as chromatin architecture and histone modifications have become crucial mechanisms for highly coordinated gene expressions, we examined such modifications. E14.5 mouse embryos were dissected into three parts along the anteroposterior axis: brain, trunk-anterior, and trunk-posterior. Then, structural changes and epigenetic modifications were analyzed along the Hoxc cluster using chromosome conformation capture and chromatin immunoprecipitation-PCR methods. Hox non-expressing brain tissues had more compact, heterochromatin-like structures together with the strong repressive mark H3K27me3 than trunk tissues. In the trunk, however, a more loose euchromatin-like topology with a reduced amount of H3K27me3 modifications were observed along the whole cluster, regardless of their potency in gene activation. The active mark H3K4me3 was rather closely associated with the collinear expression of Hoxc genes; at trunk-anterior tissues, only 3' anterior Hoxc genes were marked by H3K4me3 upon gene activation, whereas whole Hoxc genes were marked by H3K4me3 and showed expression in trunk-posterior tissues. Altogether, these results indicated that loosening of the chromatin architecture and removing H3K27me3 were not sufficient for, but rather the concomitant acquisition of H3K4me3 drove the collinear expression of Hoxc genes.     

Ornithine decarboxylase activities of a Shewanella putrefaciens which produces only diamines

Ornithine decarboxylase (ODC) activity in cell extracts of Shewanella putrefaciens was surveyed. The pH dependency of the ODC activity revealed that the bacterium has two different ODC having optimum pH at 8·25 and 6·50. They were considered to be biosynthetic and biodegradative enzymes, respectively. Their activity ratio varied when the bacterium was cultured at pH 7·0 and 6·0. Both ODC activities were inhibited by α-difluoromethylornithine but cell growth was not affected.     

Migration of neuronal cells along the anterior-posterior body axis of C. elegans: Wnts are in control

Migrating neuronal cells are directed to their final positions by an array of guidance cues. It has been shown that guidance molecules such as UNC-6/Netrin and SLT-1/Slit play a major role in controlling cell and axon migrations along the dorsal-ventral body axis. Much less is known, however, about the mechanisms that mediate migration along the anterior-posterior (AP) body axis. Recent research in Caenorhabditis elegans has uncovered an important role of the Wnt family of signalling molecules in controlling AP-directed neuronal cell migration and polarity. A common theme that emerges from these studies is that multiple Wnt proteins function in parallel as instructive cues or permissive signals to control neuronal patterning along this major body axis.     

Characterization and properties of very large inversions of the E. coli chromosome along the origin-to-terminus axis

Summary Suppression of a dnaA46 mutation by integration of plasmid R100.1 derivatives in the termination region of chromosome replication in E. coli results in medium dependence, the suppressed bacteria being sensitive to rich medium at 42° C. Derivatives of such bacteria have been selected for growth at 42° C in rich medium and we have analyzed representatives of the most frequently observed type: bacteria displaying, once cured of the suppressor plasmid, both rich-medium sensitivity and temperature sensitivity. We found, in all cases, that the chromosome had undergone a major inversion event between two inverted IS5's. One is located at 29.2 min on the chromosome map and the other at either one of two positions between 69 and 80 min. The consequences of such inversions for cell growth are discussed. Some of them result from the fact that the replication terminator T2 is located, in inverted chromosomes, close to oriC in the orientation which allows its functioning as a terminus (de Massy et al. in press). Our observations allow an estimation of the frequency of inversions arising from recombination between pairs of inverted chromosomal IS, which could be as high as 10^-2 per cell per generation. We also found that inversion reversal occurs frequently after Hfr conjugational transfer of one of the IS5's, in its wild-type location. This led us to propose a new mechanisms of recombination, in which the incoming DNA strands serve as guides to favor recombination between the resident sequences.Abbreviations Sin suppresive integration - Rms/Rmr rich medium sensitivity/resistance - Ts/Tr temperature sensitivity/resistance - Ap^r ampicillin resistance - Nal^r nalidixic acid resistance - Sp^r spectinomycin resistance - St^r streptomycin resistance - Tc^r tetracycline resistance     

In Hydra magnipapillata the activator of protein kinase C diC8 causes multiple head formation along the body axis only when accompanied by feeding, but heavy feeding alone is sufficient to cause multiple head formation

In Hydra magnipapillata additional head structures can be induced to form by daily feeding accompanied by a daily treatment with diC8, an activator of protein kinase C. Based on these results, it was proposed that the PKC- pathway plays a central role in head formation in hydra. The results described here show that ectopic structures, as well as the ectopic localization of nerve cells, can be induced by heavy feeding alone. Furthermore, diC8 treatment does not induce ectopic head structures in starved animals. DiC8 reduces the rate of budding, leading to an unusual lengthening of the body column in reasonably fed animals.     

Draft genome sequence of marine Streptomyces sp. strain W007, which produces angucyclinone antibiotics with a benz[a]anthracene skeleton

A series of angucyclinone antibiotics have been isolated from marine Streptomyces sp. strain W007 and identified. Here, a draft genome sequence of Streptomyces sp. W007 is presented. The genome contains an intact biosynthetic gene cluster for angucyclinone antibiotics, which provides insight into the combinatorial biosynthesis of angucyclinone antibiotics produced by marine streptomycetes.     

Novel patterns of the gene expression regulation in the prestalk region along the antero-posterior axis during multicellular development of Dictyostelium

Simultaneous hybridization with differentially labeled fluorescent probes for in situ hybridization analysis revealed several novel expression patterns of prestalk genes during multicellular development of Dictyostelium. Seven prestalk genes and one prespore gene (pspA) were analyzed in this study. The patterns identified here indicate that prestalk cells are more heterogeneous than previously thought. Heterogeneity was observed in peripheral prestalk tissues such as the pstAO domain of a slug and the prestalk region surrounding a stalk tube of a culminant. Heterogeneity was also observed in the core pstAB cells of the slug and immature stalk cells within the stalk tube. The upper- and lower-cups of a late culminant were also composed of several subdomains.     

Seeing the body produces limb-specific modulation of skin temperature

Vision of the body, even when non-informative about stimulation, affects somatosensory processing. We investigated whether seeing the body also modulates autonomic control in the periphery by measuring skin temperature while manipulating vision. Using a mirror box, the skin temperature was measured from left hand dorsum while participants: (i) had the illusion of seeing their left hand, (ii) had the illusion of seeing an object at the same location or (iii) looked directly at their contralateral right hand. Skin temperature of the left hand increased when participants had the illusion of directly seeing that hand but not in the other two view conditions. In experiment 2, participants viewed directly their left or right hand, or the box while we recorded both hand dorsum temperatures. Temperature increased in the viewed hand but not the contralateral hand. These results show that seeing the body produces limb-specific modulation of thermal regulation.