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1

Electronic Resource

The circumstellar imager: Direct detection of extra-solar planetary systems (1994)

Ftaclas, Christ ; Nonnenmacher, Andreas L. ; Terrile, Richard J. ; [et al.]

Springer

Astrophysics and space science 212 (1994), S. 441-452

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ISSN: 1572-946X

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The Astrometric Imaging Telescope (AIT) is designed to probe the circumstellar environment by both direct imaging and indirect astrometric measurements. The Circumstellar Imager (CI) is a coronagraphic camera and is the direct imaging component of the AIT. The CI is designed to obtain high-sensitivity images of the circumstellar region. It provides crucial non-inferential information relating to the frequency, origin, and evolution of planetary systems and all forms of circumstellar matter. Such imaging is usually limited by the scattered and diffracted light halos of the star itself, which are greatly suppressed in the CI by mating a novel high-efficiency coronagraph with a phasecompensated optical system. For faint point sources in the circumstellar region, the CI will have a sensitivity in excess of 5 magnitudes fainter than the as-designed Hubble Space Telescope (HST). Laboratory data are shown for the coronagraph, which, in a diffraction-limited environment, is capable of suppressing the stellar diffraction sidelobes by several orders of magnitude without significant sacrifice of field of view. In order to realize the high rejection levels inherent in the coronagraph design, it is necessary to limit scatter in the optical systems, imposing a mid-spatial frequency figure error requirement an order of magnitude smaller than that of the HST. Experimental data directed toward meeting this requirement are also shown.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00984548

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2

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The Astrometric Imaging Telescope: Detection of planetary systems with imaging and astrometry (1994)

Pravdo, Steven H. ; Terrile, Richard J. ; Ftaclas, Christ ; [et al.]

Springer

Astrophysics and space science 212 (1994), S. 433-440

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ISSN: 1572-946X

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The Astrometric Imaging Telescope (AIT) is a proposed spaceborne observatory whose primary goal is the detection and study of extra-solar planetary systems. It contains two instruments that use complementary techniques to address the goal. The first instrument, the Coronagraphic Imager, takes direct images of nearby stars and Jupiter-size planets. It uses a telescope with scattering-compensated optics and a high-efficiency coronagraph to separate reflected planet light from the central star light. Planet detections take hours; confirmations occur in months. With a program duration of about 2 years, about 50 stars are observed. The second instrument, the Astrometric Photometer, shares the same telescope and focal plane. It uses a Ronchi ruling that is translated across the focal plane to simultaneously measure the positions of each target star and about 25 reference stars with sufficient accuracy to detect Uranus-mass planets around hundreds of stars. Enough stars of several spectral types are observed to obtain a statistically significant measurement of the prevalence of planetary systems. This observing program takes about 10 years to complete. The combination of both instruments in a single telescope system results from a number of innovative solutions that are described in this paper.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00984547

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3

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Hyperfine structure investigation on the (3d 4)3 G 4,5 levels of47Ti (1993)

Stachowska, E. ; Fabiszisky, M. ; Christ, M. ; [et al.]

Springer

The European physical journal 27 (1993), S. 303-306

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ISSN: 1434-6079

Keywords: 31.30.Gs

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract Using two-step laser spectroscopy with the sideband technique the hyperfine structure (hfs) splittings of the levels (3d 4)3 G 4,5 in47Ti have been measured. These are the first hfs measurements of the levels belonging to the 3d N+2 configuration of the system (3d+4s) N+2. The experimental results indicate a strong increase of the core polarization effect due to excitation of both 4s-electrons to the open 3d-shell.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01437460

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4

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In vivo effects of vascular endothelial growth factor on the chicken chorioallantoic membrane (1993)

Wilting, Jörg ; Christ, Bodo ; Bokeloh, Matthias ; [et al.]

Springer

Cell & tissue research 274 (1993), S. 163-172

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ISSN: 1432-0878

Keywords: Chorioallantoic membrane ; Angiogenesis ; Vascular endothelial growth factor (VEGF) ; Basic fibroblast growth factor (bFGF) ; Heparin ; Domestic fowl (White Leghorn)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract The effect of vascular endothelial growth factor (VEGF165) on the chorioallantoic membrane (CAM) of 13-day-old chick embryos was studied. The factor was applied in doses of 0.5–4 μg for a period of up to 4 days. Macroscopical, histological and immunohistological studies were carried out. The localization of the factor was examined with an anti-VEGF antibody. The mitogenicity of VEGF165 and basic fibroblast growth factor (bFGF) were studied by means of the BrdU-anti-BrdU method. Furthermore, the effect of heparin alone and in combination with VEGF165 was investigated. VEGF165 specifically induces angiogenesis in doses of 0.5 μg and more. A brush-like formation of blood vessels can be seen in the region of the precapillary vessels. Angiogenesis also takes place in the region of the capillaries and the venules. Histologically we found indications of sprouting as well as of intussusceptive capillary growth. The presence of the factor in the application area could be demonstrated with the anti-VEGF antibody for a period of 3 days. The factor is located in the chorionic epithelium and the intraepithelial capillaries. The BrdU-studies show that VEGF165 induces strong endothelial cell proliferation, whereas bFGF elicits fibrocyte proliferation and minor endothelial cell proliferation. Heparin induces squamous metaplasia of the chorionic and allantoic epithelium in combination with an aggregation of fibrocytes. We could not detect any enhancement of VEGF165 by heparin.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00327997

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5

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Effects of calcium channel blockers on the contractility of the filariidAcanthocheilonema viteae (1992)

Christ, Daryl ; Stillson, Tod

Springer

Parasitology research 78 (1992), S. 489-494

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ISSN: 1432-1955

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract The role of calcium in muscle contractility was explored in the filarial nematodeAcanthocheilonema viteae (Dipetalonema viteae). The parasite was slit open longitudinally and mounted in a smooth-muscle chamber that had been filled with aerated (95% N2/5% CO2) physiological solution at 37°C. Nifedipine (10−6 m) and cadmium (3×10−5 m) reduced the spontaneous isotonic contractions ofA. viteae, whereas verapamil (10−5 m) and diltiazem (10−5 m) enhanced them. The effects of nifedipine and verapamil did not appear to be due to the solvent ethanol. All of the drugs reduced the maximal contraction induced by acetylcholine (ACh, 10−5 m), although nifedipine was the most potent. After the exposure of worm preparations to a calcium-free medium containing ethyleneglycol-bis-(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA, 10−4 m) for 1 h, application of ACh (10−5 m) induced a small, transient contraction. Subsequent applications of ACh in this medium had no effect. Thus, the nematode muscle contraction appears to depend on extracellular calcium. Nifedipine, diltiazem, and verapamil could act by reducing the calcium influx across the muscle membrane.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00931569

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6

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Contractions of the filariidAcanthocheilonema viteae induced by potassium chloride (1994)

Christ, Daryl ; Oh, Ju ; Saz, Howard J.

Springer

Parasitology research 80 (1994), S. 449-453

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ISSN: 1432-1955

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract The effects of K+ on muscle contractility were explored in the filarial nematodeAcanthocheilonema viteae (Dipetalonema viteae). The parasite was slit open longitudinally and mounted in a smooth muscle chamber that was filled with aerated (95% N2−5% CO2) physiological solution at 37°C. KCl at concentrations ranging from 20 to 100 mM induced a rapid isotonic contraction of the filarial muscle. The maximal response from KCl was similar to the maximal response to acetylcholine chloride (ACh). When KCl was applied for several minutes, tolerance frequently occurred. Contractions were also induced by K2SO4 but not by NaCl, Na2SO4 or sucrose. Nifedipine was more than 10 times as potent in reducing the KCl-induced contraction as in reducing that caused by ACh. The KCl-induced contraction was abolished in a Ca-free physiological medium containing ethyleneglycol-bis-(β-aminoethyl ether)N,N,N′,N′-tetraacetic acid (EGTA, 10−4 M). Low [Ca2+]/[Mg2+] solutions blocked the spontaneous activity, the KCl-induced contractions, and the ACh-induced contractions. KCl also induced contractions in denervated muscle strips, supporting the hypothesis that K+ acts directly on the muscle cells. These results indicate that K+ can depolarize the muscle membrane and induce a muscle contraction that is dependent on extracellular calcium ions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00932689

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7

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Distribution of extracellular matrix components in nuchal skin from fetuses carrying trisomy 18 and trisomy 21 (1994)

Brand-Saberi, B. ; Epperlein, H. H. ; Romanos, G. E. ; [et al.]

Springer

Cell & tissue research 277 (1994), S. 465-475

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ISSN: 1432-0878

Keywords: Key words: Trisomy 18 (Edwards' syndrome) ; Trisomy 21 (Down's syndrome) ; Nuchal oedema ; Extracellular matrix ; Man

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract. We have investigated histologically the elevations of the skin in dorsal and lateral neck (nuchal) regions of human fetuses carrying karyotypes of trisomy 18 (Edwards' syndrome) and trisomy 21 (Down's syndrome). Cavities filled with interstitial fluid were found in the dermis, epidermal basement membrane and occasionally in the epidermis of trisomy-18 fetuses, but were not delineated by an epithelium or basement membrane as judged by the absence of immunostaining for laminin, collagen IV and collagen VII. Dilated vessels were also found at the interface between dermis and subcutis. Neither normal fetal skin nor that of trisomy-21 fetuses contained cavities or dilated vessels. In order to detect possible alterations of the extracellular matrix in trisomy-18 and trisomy-21 skin, the distribution of glycoproteins, glycosaminoglycans and proteoglycans was studied immunohistochemically. In trisomy-21 and control skin, the dermis stained intensely for fibronectin, whereas the subcutis reacted only weakly. In trisomy-18 skin, the stronger staining for fibronectin appeared in the subcutis, and the prevailing collagen type was collagen III, collagen type I being absent. In the skin of trisomy-21 fetuses, collagen VI was more irregularly arranged and densely packed, whereas collagen I was more widely spaced than in normal fetuses. More hyaluronan was present in the dermis and subcutis of trisomy-21 fetuses than in that of trisomy-18 and control fetuses. A correlation seems to exist between undelimited cavities and collagen III in trisomy-18 skin, and between hyaluronan and the specific arrangement of collagen in trisomy-21 skin.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00300219

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8

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Distribution of extracellular matrix components in nuchal skin from fetuses carrying trisomy 18 and trisomy 21 (1994)

Brand-Saberi, B. ; Epperlein, H. H. ; Romanos, G. E. ; [et al.]

Springer

Cell & tissue research 277 (1994), S. 465-475

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ISSN: 1432-0878

Keywords: Trisomy 18 (Edwards' syndrome) ; Trisomy 21 (Down's syndrome) ; Nuchal oedema ; Extracellular matrix ; Man

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract We have investigated histologically the elevations of the skin in dorsal and lateral neck (nuchal) regions of human fetuses carrying karyotypes of trisomy 18 (Edwards' syndrome) and trisomy 21 (Down's syndrome). Cavities filled with interstitial fluid were found in the dermis, epidermal basement membrane and occasionally in the epidermis of trisomy-18 fetuses, but were not delineated by an epithelium or basement membrane as judged by the absence of immunostaining for laminin, collagen IV and collagen VII. Dilated vessels were also found at the interface between dermis and subcutis. Neither normal fetal skin nor that of trisomy-21 fetuses contained cavities or dilated vessels. In order to detect possible alterations of the extracellular matrix in trisomy-18 and trisomy-21 skin, the distribution of glycoproteins, glycosaminoglycans and proteoglycans was studied immunohistochemically. In trisomy-21 and control skin, the dermis stained intensely for fibronectin, whereas the subcutis reacted only weakly. In trisomy-18 skin, the stronger staining for fibronectin appeared in the subcutis, and the prevailing collagen type was collagen III, collagen type I being absent. In the skin of trisomy-21 fetuses, collagen VI was more irregularly arranged and densely packed, whereas collagen I was more widely spaced than in normal fetuses. More hyaluronan was present in the dermis and subcutis of trisomy-21 fetuses than in that of trisomy-18 and control fetuses. A correlation seems to exist between undelimited cavities and collagen III in trisomy-18 skin, and between hyaluronan and the specific arrangement of collagen in trisomy-21 skin.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00300219

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