Excited-State Phase Diagram of a Ferromagnetic Quantum Gas.

The ground-state phases of a quantum many-body system are characterized by an order parameter, which changes abruptly at quantum phase transitions when an external control parameter is varied. Interestingly, these concepts may be extended to excited states, for which it is possible to define equivalent excited-state quantum phase transitions. However, the experimental mapping of a phase diagram of excited quantum states has not yet been realized. Here we present the experimental determination of the excited-state phase diagram of an atomic ferromagnetic quantum gas, where, crucially, the excitation energy is one of the control parameters. The obtained phase diagram exemplifies how the extensive Hilbert state of quantum many-body systems can be structured by the measurement of well-defined order parameters.

Momentum Entanglement for Atom Interferometry.

Compared to light interferometers, the flux in cold-atom interferometers is low and the associated shot noise is large. Sensitivities beyond these limitations require the preparation of entangled atoms in different momentum modes. Here, we demonstrate a source of entangled atoms that is compatible with state-of-the-art interferometers. Entanglement is transferred from the spin degree of freedom of a Bose-Einstein condensate to well-separated momentum modes, witnessed by a squeezing parameter of -3.1(8) dB. Entanglement-enhanced atom interferometers promise unprecedented sensitivities for quantum gradiometers or gravitational wave detectors.

Heralded Generation of Macroscopic Superposition States in a Spinor Bose-Einstein Condensate.

Macroscopic superposition states enable fundamental tests of quantum mechanics and hold a huge potential in metrology, sensing, and other quantum technologies. We propose to generate macroscopic superposition states of a large number of atoms in the ground state of a spin-1 Bose-Einstein condensate. Measuring the number of particles in one mode prepares with large probability highly entangled macroscopic superposition states in the two remaining modes. The macroscopic superposition states are heralded by the measurement outcome. Our protocol is robust under realistic conditions in current experiments, including finite adiabaticity, particle loss, and measurement uncertainty.

Hybrid performance in taro (Colocasia esculenta) in relation to genetic dissimilarity of parents.

Taro (Colocasia esculenta) breeding, as other root crop breeding, is based on the production and evaluation of large numbers of hybrids. The selection of parents is based on their phenotypic value in the absence of information concerning general combining ability (GCA), specific combining ability (SCA), or genetic distances between varieties. By combining data from heritability trials and from genetic diversity studies conducted with AFLP and SSR markers, we aimed at studying the relationship between hybrid vigour and genetic dissimilarity between parents. The traits studied included number of suckers, corm weight, corm dimensions, and dry matter content. Correlation coefficients between hybrid gain and dissimilarity values were calculated. The prediction of hybrid performance based on the mid-parent value was compared to the prediction based on a modified expression that takes into account the genetic relationships between parents. Correlations were all but one positive but not statistically significant for all traits, with the exception of the number of suckers, when using SSR markers for dissimilarity calculations. Accordingly, the genetic dissimilarities in the prediction of hybrid performances did not increase the correlation between predicted and observed hybrid vigour values. However, large differences were observed among the residual means from the regression between predicted and observed values when using AFLP or SSR markers, mainly due to the much higher polymorphism revealed by the latter. Models need to be further adapted to the type of molecular marker used, since their ability to reveal different rates of polymorphism will have a direct incidence on the calculation of genetic dissimilarities between genotypes. Nevertheless, since SSR markers are more polymorphic and more informative than AFLP markers, they should be preferentially used for these studies. Low genetic dissimilarity of parents yielded weak heterosis effects and future studies need to be conducted by using a broader genetic base. This is the first study assessing the relationship of hybrid vigour with the genetic distances between parents, conducted on a tropical root crop.

[Surgical treatment of spinal stenosis]. / Operative Therapie des engen Spinalkanals.

Surgical treatment of lumbar spinal stenosis is aimed at decompressing the structures of the spinal canal. Several surgical techniques have been described over the last few years. This article gives a survey of the surgical procedures used for the treatment of spinal stenosis. When comparing and discussing indications and current surgical techniques used for spinal stenosis, one can describe some general tendencies: if the symptoms are severe or disabling and do not respond to appropriate conservative treatment, or if the patient is not able to cope with the pain any longer and views his or her quality of life as unacceptable, surgery is indicated. If the symptoms are mainly radicular, (microsurgical) decompression should be performed. If back pain is the main problem combined with preoperative evidence of segmental instability, spondylolisthesis, or scoliosis, one should consider spinal fusion in addition to an appropriate decompression. Further investigations are necessary to exactly find out the appropriate indications for a fusion and to answer the question of whether spinal instrumentation should be used.

[History of the treatment of spinal diseases]. / Geschichte der Behandlung von Wirbelsäulenerkrankungen.

Identification and treatment of spinal disorders have been described for thousands of years. Nevertheless, systematic operative treatment was more or less impossible until about 200 years ago. During the second half of the last century, spinal surgery developed rapidly due to several technical improvements. This article summarizes the main aspects of the historical development of spinal surgery.

32/67-kD laminin receptor expression in human colonic neoplasia: elevated transcript levels correlate with the degree of epithelial dysplasia.

OBJECTIVE: The 32/67-kD laminin receptor is thought to be involved in tumor cell migration and metastasis formation, and enhanced expression was observed in human colorectal carcinoma. Our objective was to investigate further the expression of the 32/67-kD laminin receptor RNA in human colonic carcinogenesis. METHODS: We obtained sections of human colonic tissues in various stages of malignant transformation and analyzed them by in situ hybridization. RESULTS: Normal colonic mucosa displayed a gradient between crypt base and surface epithelium with lowest receptor RNA levels in superficial epithelial cells. Increased laminin receptor RNA expression was observed in epithelial cells of adenomas with positive correlation between transcript levels and the degree of epithelial dysplasia. At variance with published results, we did not observe significant differences in 32/67-kD laminin receptor transcripts between adenomas with high-grade dysplasia and invasive adenocarcinoma. However, adenocarcinoma metastases displayed significantly higher laminin receptor RNA levels than high-grade adenomas and primary carcinomas. CONCLUSIONS: We propose a two-step mechanism which controls first, upregulation of laminin receptor RNA before the acquisition of an invasive phenotype in dysplastic epithelial cells, and second, a further upregulation in metastatic cells during the adenoma-carcinoma sequence of the colon.

Control of growth and differentiation by Drosophila RasGAP, a homolog of p120 Ras-GTPase-activating protein.

Mammalian Ras GTPase-activating protein (GAP), p120 Ras-GAP, has been implicated as both a downregulator and effector of Ras proteins, but its precise role in Ras-mediated signal transduction pathways is unclear. To begin a genetic analysis of the role of p120 Ras-GAP we identified a homolog from the fruit fly Drosophila melanogaster through its ability to complement the sterility of a Schizosaccharomyces pombe (fission yeast) gap1 mutant strain. Like its mammalian homolog, Drosophila RasGAP stimulated the intrinsic GTPase activity of normal mammalian H-Ras but not that of the oncogenic Val12 mutant. RasGAP was tyrosine phosphorylated in embryos and its Src homology 2 (SH2) domains could bind in vitro to a small number of tyrosine-phosphorylated proteins expressed at various developmental stages. Ectopic expression of RasGAP in the wing imaginal disc reduced the size of the adult wing by up to 45% and suppressed ectopic wing vein formation caused by expression of activated forms of Breathless and Heartless, two Drosophila receptor tyrosine kinases of the fibroblast growth factor receptor family. The in vivo effects of RasGAP overexpression required intact SH2 domains, indicating that intracellular localization of RasGAP through SH2-phosphotyrosine interactions is important for its activity. These results show that RasGAP can function as an inhibitor of signaling pathways mediated by Ras and receptor tyrosine kinases in vivo. Genetic interactions, however, suggested a Ras-independent role for RasGAP in the regulation of growth. The system described here should enable genetic screens to be performed to identify regulators and effectors of p120 Ras-GAP.

Opposing actions of CSW and RasGAP modulate the strength of Torso RTK signaling in the Drosophila terminal pathway.

In Drosophila, specification of embryonic terminal cells is controlled by the Torso receptor tyrosine kinase. Here, we analyze the molecular basis of positive (Y630) and negative (Y918) phosphotyrosine (pY) signaling sites on Torso. We find that the Drosophila homolog of RasGAP associates with pY918 and is a negative effector of Torso signaling. Further, we show that the tyrosine phosphatase Corkscrew (CSW), which associates with pY630, specifically dephosphorylates the negative pY918 Torso signaling site, thus identifying Torso to be a substrate of CSW in the terminal pathway. CSW also serves as an adaptor protein for DRK binding, physically linking Torso to Ras activation. The opposing actions of CSW and RasGAP modulate the strength of the Torso signal, contributing to the establishment of precise boundaries for terminal structure development.

First Report of Leaf Scald Disease and Ratoon Stunting Disease of Sugarcane in French Guyana.

In December 1995, leaf scald symptoms were observed in sugarcane (Saccharum sp.) cultivar B64277 in French Guyana. Symptomatic plants occurred both in a sugarcane germplasm collection near the road between Sinnamary and Saint-Elie and in a nursery near Sinnamary. Sugarcane imported from Martinique had been used to establish the germplasm collection that in turn had been used to establish the nursery. Ten-month-old mature plants in the germplasm collection had abnormal side shoots on the lower part of the stalks and suckers (nonmillable stalks) with white scalded areas on leaves. Leaves on 1-month-old shoots in the nursery exhibited chlorosis and white, pencil-line streaks. Samples prepared from symptomatic stalks from the two locations were plated on a selective medium (1), and two isolates of Xanthomonas albilineans were recovered. Both of these isolates caused leaf scald symptoms on leaves of sugarcane cultivar B69566 inoculated by a decapitation technique, and belong to serovar 3 previously reported in the Caribbean from Guadeloupe, Martinique, and St. Kitts. The RFLP (restriction fragment length polymorphism) pattern of these two isolates was different from the 54 patterns among 218 other strains collected throughout the world (2), but similar to the pattern of a strain of serovar 3 from Martinique. This indicated that the pathogen might have been introduced with cuttings imported from Martinique. Three stalks of mature cane from varieties B5992, B64277, and R570 from the germplasm collection were tested for the presence of Clavibacter xyli subsp. xyli, causal agent of ratoon stunting disease. Immunofluorescence tests on sap (3) revealed the presence of the pathogen in the three stalks of B64277. All sugarcane plants in the nursery and the germplasm collection were destroyed by the use of glyphosate sprays in January 1996 in an attempt to arrest the spread of the two bacterial pathogens. In order to obtain healthy seed cane for future planting, a new germplasm collection of 0.6 ha and consisting of 11 cultivars was planted in January 1996 with disease-free, tissue-cultured plants provided by the CIRAD sugarcane breeding station in Guadeloupe. References: (1) M. J. Davis et al. Plant Dis. 78:78, 1994. (2) M. J. Davis et al. Phytopathology 87:316, 1997. (3) M. J. Davis and J. L. Dean. Plant Dis. 68:896, 1984.

Resistance to Leaf Scald Disease Is Associated with Limited Colonization of Sugarcane and Wild Relatives by Xanthomonas albilineans.

ABSTRACT A streptomycin- and rifampicin-resistant mutant of Xanthomonas al-bilineans was used to study symptom expression of leaf scald disease (LSD) and colonization of sugarcane (Saccharum spp.) and its wild relatives by this bacterial pathogen. A total of 40 sugarcane cultivars and 15 clones from the Saccharum complex that differed in resistance to LSD were inoculated by a decapitation technique in both field and greenhouse experiments. In the plant crop, disease severity varied between 0 for the most resistant genotypes and 100 for the most susceptible ones. Resistance to LSD was characterized by limited colonization of the host plant by X. albilineans. Although almost all genotypes were colonized by the pathogen, the greatest bacterial population densities were found in the susceptible cultivars. There was a high correlation between disease severity and pathogen population in the apex. Several genotypes exhibited no or slight symptoms even though they were highly colonized in the upper and/or basal nodes of stalks. Two mechanisms, therefore, may play an important role in resistance to LSD: resistance to colonization of the apex, which is characterized by absence of symptoms, and resistance to colonization of the upper and lower parts of the stalk. In contrast, disease severity and pathogen population densities in the first ratoon crop in the field were nil or very low in the stalks, except for the highly susceptible cv. CP68-1026. Sugarcane ratoons, therefore, may recover from the disease after plant cane infection. Nevertheless, because low levels of the pathogen were still detected in some stalks, it is possible that LSD could develop from latent infections if favorable environmental conditions occur.

The Candida albicans HYR1 gene, which is activated in response to hyphal development, belongs to a gene family encoding yeast cell wall proteins.

A hyphally regulated gene (HYR1) from the dimorphic human pathogenic fungus Candida albicans was isolated and characterized. Northern (RNA) analyses showed that the HYR1 mRNA was induced specifically in response to hyphal development when morphogenesis was stimulated by serum addition and temperature elevation, increases in both culture pH and temperature, or N-acetylglucosamine addition. The HYR1 gene sequence revealed a 937-codon open reading frame capable of encoding a protein with an N-terminal signal sequence, a C-terminal glycosylphosphatidylinositol-anchoring domain, 17 potential N glycosylation sites, and a large domain rich in serine and threonine (51% of 230 residues). These features are observed in many yeast cell wall proteins, but no homologs are present in the databases. In addition, Hyr1p contained a second domain rich in glycine, serine, and asparagine (79% of 239 residues). The HYR1 locus in C. albicans CAI4 was disrupted by "Ura-blasting," but the resulting homozygous delta hyr1/delta hyr1 null mutant displayed no obvious morphological phenotype. The growth rates for yeast cells and hyphae and the kinetics of germ tube formation in the null mutant were unaffected. Aberrant expression of HYR1 in yeast cells, when an ADH1-HYR1 fusion was used, did not stimulate hyphal formation in C. albicans or pseudohyphal growth in Saccharomyces cerevisiae. HYR1 appears to encode a nonessential component of the hyphal cell wall.

Characterisation of the double genome structure of modern sugarcane cultivars (Saccharum spp.) by molecular cytogenetics.

Cultivated sugarcane clones (Saccharum spp., 2n=100 to 130) are derived from complex interspecific hybridizations between the species S. officinarum and S. spontaneum. Using comparative genomic DNA in situ hybridization, we demonstrated that it is possible to distinguish the chromosomes contributed by these two species in an interspecific F1 hybrid and a cultivated clone, R570. In the interspecific F1 studied, we observed n + n transmission of the parental chromosomes instead of the peculiar 2n + n transmission usually described in such crosses. Among the chromosomes of cultivar R570 (2n = 107-115) about 10% were identified as originating from S. spontaneum and about 10% were identified as recombinant chromosomes between the two species S. officinarum and S. spontaneum. This demonstrated for the first time the occurrence of recombination between the chromosomes of these two species. The rDNA sites were located by in situ hybridization in these two species and the cultivar R570. This supported different basic chromosome numbers and chromosome structural differences between the two species and provided a first bridge between physical and genetical mapping in sugarcane.

RFLP mapping in cultivated sugarcane (Saccharum spp.): genome organization in a highly polyploid and aneuploid interspecific hybrid.

Sugarcane cultivars are polyploid, aneuploid, interspecific hybrids between the domesticated species Saccharum officinarum and the wild relative S. spontaneum. Cultivar chromosome numbers range from 100 to 130 with approximately 10% contributed by S. spontaneum. We have undertaken a mapping study on the progeny of a selfed cultivar, R570, to analyze this complex genome structure. A set of 128 restriction fragment length polymorphism probes and one isozyme was used. Four hundred and eight markers were placed onto 96 cosegregation groups, based on linkages in coupling only. These groups could tentatively be assembled into 10 basic linkage groups on the basis of common probes. Origin of markers was investigated for 61 probes and the isozyme, leading to the identification of 80 S. officinarum and 66 S. spontaneum derived markers, respectively. Their distribution in cosegregation groups showed better map coverage for the S. spontaneum than for the S. officinarum genome fraction and occasional recombination between the two genomes. The study of repulsions between markers suggested the prevalence of random pairing between chromosomes, typical of autopolyploids. However, cases of preferential pairing between S. spontaneum chromosomes were also detected. A tentative Saccharum map was constructed by pooling linkage information for each linkage group.

Constitutive activation of the Saccharomyces cerevisiae mating response pathway by a MAP kinase kinase from Candida albicans.

The HST7 gene of Candida albicans encodes a protein with structural similarity to MAP kinase kinases. Expression of this gene in Saccharomyces cerevisiae complements disruption of the Ste7 MAP kinase kinase required for both mating in haploid cells and pseudohyphal growth in diploids. However, Hst7 expression does not complement loss of either the Pbs2 (Hog4) MAP kinase kinase required for response to high osmolarity, or loss of the Mkk1 and Mkk2 MAP kinase kinases required for proper cell wall biosynthesis. Intriguingly, HST7 acts as a hyperactive allele of STE7; expression of Hst7 activates the mating pathway even in the absence of upstream signaling components including the Ste7 regulator Ste11, elevates the basal level of the pheromone-inducible FUS1 gene, and amplifies the pseudohyphal growth response in diploid cells. Thus Hst7 appears to be at least partially independent of upstream activators or regulators, but selective in its activity on downstream target MAP kinases. Creation of Hst7/Ste7 hybrid proteins revealed that the C-terminal two-thirds of Hst7, which contains the protein kinase domain, is sufficient to confer this partial independence of upstream activators.

[Tenon-plasty and early keratoplasty in severe chemical eye burns]. / Tenon-Plastik und Frühkeratoplastik bei schwerstverätzten Augen.

In severe eye burns with destruction of extensive areas of the conjunctiva and epibulbar tissue, Tenon plasty has proved to be successful. Because the epithelium fails to cover the denuded stroma, the corneal surface must be protected by an artificial epithelium. If necrolysis occurs, a tectonic keratoplasty must be performed early. The clinical courses of 12 patients with 14 very severely burned eyes are reported. In addition to Tenon plasty, early penetrating keratoplasies with large diameters 10-16 mm were performed up to 3 months after the accident. The follow-up time was between 6 and 34 months (mean 15.1 months). In five cases the Tenon tissue showed marked inflammation, and the keratoplasties developed large, persistent epithelial defects and had to be covered by conjunctiva. In the other cases it was possible to preserve a healthy epithelial layer by applying soft contact lenses. In 79% of the cases an endothelial graft rejection was observed. In about 50% the transplants were lost. Early keratoplasties are mainly for tectonic repair in severely burned eyes. Optical rehabilitation was achieved in only a few cases.

Identification and characterisation of sugarcane intergeneric hybrids, Saccharum officinarum x Erianthus arundinaceus, with molecular markers and DNA in situ hybridisation.

Molecular markers were used to characterise sugarcane intergeneric hybrids between S. officinarum and E. arundinaceus. Very simple diagnostic tools for hybrid identification among the progeny were derived from isozyme electrophoresis and a sequence-tagged PCR. Two enzyme systems (GOT and MDH B) and PCR amplification revealing spacer-size variation in the 5s-rDNA cluster were found most convenient. Specific characterisation of the two genomic components was possible using RFLP and in situ hybridisation. The strong molecular differentiation between S. officinarum and E. arundinaceus allows the identification of numerous Erianthus-specific RFLP bands in the hybrids. Genomic DNA in situ hybridisation allows for the differentiation of the chromosomes contributed by S. officinarum and E. arundinaceus in chromosome preparations of the hybrids. In situ hybridisation with the 18s-5.8s-25s rDNA probe highlights the basic chromosome numbers in the two parental species. The potential of these techniques to monitor the Erianthus genome during the introgression process is discussed.

A molecular approach to unraveling the genetics of sugarcane, a complex polyploid of the Andropogoneae tribe.

Modern sugarcane varieties are complex aneuploids and typically have chromosome numbers in the 100-125 range with about 5-10% of them contributed by wild relatives, mainly Saccharum spontaneum, and the rest by S. officinarum. This particular genomic constitution was found favorable for mapping the S. spontaneum genome, using maize as a diploid reference for comparison. We conducted an analysis of 32 individuals derived from the selfing of variety SP 701006 using four isozymes and 53 maize probes which covered the whole maize genome. A total of 348 segregating bands were generated. Highly significant cosegregations enabled us to place 94 markers into 25 cosegregation groups. Eighteen of these groups involved S. spontaneum specific markers and might therefore mark S. spontaneum chromosomes in segregation. On the basis of probes in common, the 25 cosegregation groups could be assembled into eight tentative linkage groups, of which seven describe S. spontaneum chromosomes. A large degree of synteny between sugarcane and maize could be inferred, with a much lower rate of recombination in sugarcane.

Biochemical genetic markers in sugarcane.

Isozyme variation was used to identify biochemical markers of potential utility in sugarcane genetics and breeding. Electrophoretic polymorphism was surveyed for nine enzymes among 39 wild and noble sugarcane clones, belonging to the species most closely related to modern varieties. Up to 114 distinct bands showing presence versus absence type of variation were revealed and used for qualitative characterization of the materials. Multivariate analysis of the data isolated the Erianthus clone sampled and separated the Saccharum spontaneum clones from the S. robustum and S. officinarum clones; the latter two were not differentiated from one another. The analysis of self-progenies of a 2n=112 S. spontaneum and of a commercial variety showed examples of mono- and polyfactorial segregations. Within the progeny of the variety, co-segregation of two isozymes frequent in S. spontaneum led to them being assigned to a single chromosome initially contributed by a S. spontaneum donor. This illustrates how combined survey of ancestral species and segregation analysis in modern breeding materials should permit using the lack of interspecific cross-over to establish linkage groups in a sugarcane genome.