Showing papers by "Martin Luther University of Halle-Wittenberg published in 1988"

Thin Stage I Primary Cutaneous Malignant Melanoma

Abstract: Although wide surgical excision is the accepted treatment for thin malignant melanomas, there is reason to believe that narrower margins may be adequate. We conducted a randomized prospective study to assess the efficacy of narrow excision (excision with 1-cm margins) for primary melanomas no thicker than 2 mm. Narrow excision was performed in 305 patients, and wide excision (margins of 3 cm or more) was performed in 307 patients. The major prognostic criteria were well balanced in the two groups. The mean thickness of melanomas was 0.99 mm in the narrow-excision group and 1.02 mm in the wide-excision group. The subsequent development of metastatic disease involving regional nodes and distant organs was not different in the two groups (4.6 and 2.3 percent, respectively, in the narrow-excision group, as compared with 6.5 and 2.6 percent in the wide-excision group). Disease-free survival rates and overall survival rates (mean follow-up period, 55 months) were also similar in the two groups. Only three patients had a local recurrence as a first relapse. All had undergone narrow excision, and each had a primary melanoma with a thickness of 1 mm or more. The absence of local recurrence in the group of patients with a primary melanoma thinner than 1 mm and the very low rate of local recurrences indicate that narrow excision is a safe and effective procedure for such patients.

On the Multipole Character of the X‐Ray Transitions in the Pre‐Edge Structure of Fe K Absorption Spectra. An Experimental Study

Abstract: The K absorption edge of pure Fe and the pre-edge Fe K absorption of FeS2 (pyrite), Fe2O3 (hematite), and FeCO3 (siderite) are investigated with single crystal absorbers of these materials using linearly polarized synchrotron X-radiation. From the angular dependence of the pre-edge K absorption the existence of predominantly ligand-field-induced dipole transition in Fe2O3 and of quadrupole transitions in FeCO3 is concluded. The multipole character and the mechanism of the pre-edge K absorption are discussed. Die K-Absorptionskante von reinem Fe und die Fe K-Vorkantenabsorption von FeS2 (Pyrit), Fe2O3 (Hamatit) und FeCO3 (Siderit) werden an einkristallinen Absorbern dieser Materialien mit linear polarisierter Synchrotron-Rontgenstrahlung untersucht. Aus der Winkelabhangigkeit der K-Vorkantenabsorption wird auf das Auftreten von uberwiegend ligandenfeldinduzierten Dipolubergangen im Fe2O3 und von Quadrupolubergangen im FeCO3 geschlossen. Der Multipolcharakter und der Mechanismus der K-Vorkantenabsorption werden diskutiert.

Field-induced phase transition in Pb (Mg1/3Nb2/3)O3 single crystals

Abstract: Hysteresis loops and remanent polarization below Tt -70 °C suggest that a ferroelectric phase can be induced in PMN crystals by an electric field parallel to [110], [111], and [001]. This could be corroborated, however, only for the two former cases by optical investigations and X-ray analysis.

Investigation of the Valence Band Structure of Thermoelectric (Bi1−xSbx)2Te3 Single Crystals

Abstract: Using combined optical-spectroscopic and transport investigations it is succeeded for the first time to determine all relevant valence band data for the whole series of mixed crystals (Bi1−xSbx)2Te3 (0 ≦ x ≦ 1). The reflectivity of polarized infrared light including its anisotropy is measured in the wave number range of 300 to 4000 cm−-1. In addition to the spectra the Hall coefficients ϱ123 and ϱ312, the electrical conductivity σ ⟂ c, and the Seebeck coefficient S ⟂ c are also given. In term of a six-valley band model and scattering by acoustical phonons all experimental data are consistently described. The main axis masses m, the ellipsoid tilt angle ϑ, the effective density-of-states mass md, and the susceptibility masses m,∥c are calculated in dependence on composition, also the Fermi level EF, the carrier density p, the mobility μ ⟂ c, the high frequency dielectric constant ϵ∞⟂,∥c, and the relaxation time τopt. For the first time the structure factors in the Hall coefficients are given. In the plot m(x) the distinct maxima of m and md near x = 0.8 are evident and important for the application of these substances. Unter Verwendung von kombinierten optisch-spektroskopischen und Transportuntersuchungen ist es erstmals gelungen, alle relevanten Valenzbanddaten fur die gesamte Mischkristallreihe (Bi1−xSbx)2Te3 (0 ≦ x ≦ 1) zu ermitteln. Die Reflektivitat von polarisiertem Infrarotlicht wird einschlieslich ihrer Anisotropie im Wellenzahlbereich von 300 bis 4000 cm−1 gemessen. Zusatzlich zu den Spektren werden die Hallkoeffizienten ϱ123 und ϱ512, die elektrische Leitfahigkeit σ ⟂ c und der Seebeck-Koeffizient S ⟂ c angegeben. Alle experimentellen Daten werden durch ein Sechs-Tal-Bandmodell und akustische Gitterstreuung konsistent beschrieben. Die Hauptachsenmassen m, der Ellipsoid-Neigungswinkel ϑ, die effektive Zustandsdichtemasse md und die Suszeptibilitatsmassen m,∥c werden in Abhangigkeit von der Zusammensetzung berechnet; ebenso das Ferminiveau EF, die Tragerdichte p, die Beweglichkeit μ⟂c, die Hochfrequenz-Dielektrizitatskonstante ϵ∞⟂,∥,c und die Relaxationszeit τopt. Erstmals werden die Strukturfaktoren der Hallkoeffizienten angegeben. Im Verlauf m(x) sind die Maxima von m und md nahe x = 0,8 auffallend und bedeutend fur die Anwendung dieser Substanzen.

Efficient K+ buffering by mammalian retinal glial cells is due to cooperation of specialized ion channels.

Abstract: Radial glial (Muller) cells were isolated from rabbit retinae by papaine and mechanical dissociation. Regional membrane properties of these cells were studied by using the patch-clamp technique. In the course of our experiments, we found three distinct types of large K+ conducting channels. The vitread process membrane was dominated by high conductance inwardly rectifying (HCR) channels which carried, in the open state, inward currents along a conductance of about 105 pS (symmetrical solutions with 140 mM K+) but almost no outward currents. In the membrane of the soma and the proximal distal process, we found low conductance inwardly rectifying (LCR) channels which had an open state-conductance of about 60 pS and showed rather weak rectification. The endfoot membrane, on the other hand, was found to contain non-rectifying very high conductance (VHC) channels with an open state-conductance of about 360 pS (same solutions). These results suggest that mammalian Muller cells express regional membrane specializations which are optimized to carry spatial buffering currents of excess K+ ions.

Modulation of calcium channel currents in guinea-pig single ventricular heart cells by the dihydropyridine Bay K 8644.

Abstract: 1. A single glass micropipette voltage clamp technique with intracellular dialysis was used to study Ba2+ currents in isolated ventricular cells from guinea-pig hearts. Effects of the 1,4-dihydropyridine Bay K 8644 on whole-cell currents were evaluated at 37 degrees C. 2. Bay K 8644 increased the Ba2+ peak currents at test potentials between -50 and +20 mV and shifted the current-voltage relationships towards hyperpolarizing potentials (leftward shift for Ca2+ channel activation, 13.8 +/- 4.1 mV; n = 9; Bay K 8644, 5 mumol/l). 3. The peak times of the Ba2+ currents were diminished over the voltage range tested between -40 and +20 mV after Bay K 8644 in parallel with a shortening of the time constant of activation that was estimated from fits of the recorded currents with a d2f model. 4. The decay of the Ba2+ currents was fitted with two exponentials including a pedestal. The compound Bay K 8644 accelerated the fast decay over the whole voltage range. The amplitude of the rapidly inactivated component of the Ba2+ currents was strikingly increased after application of Bay K 8644. 5. The steady-state inactivation using a 0.5 or 5 s pre-pulse was shifted towards hyperpolarizing potentials (leftward shift 10.3 +/- 5.2 mV; n = 4; Bay K 8644, 5 mumol/l). 6. The change in the time course of Bay K 8644-modified Ba2+ currents cannot be described solely by a decrease of the backward rate coefficient from an open to a closed state of the Ca2+ channel (Sanguinetti, Krafte & Kass, 1986). The described effects of Bay K 8644 on the inactivation can be both qualitatively and quantitatively described by a model of current-dependent inactivation (Standen & Stanfield, 1982), assuming a lower affinity of an internal binding site for Ba2+ than for Ca2+.

Calcium block of guinea-pig heart sodium channels with and without modification by the piperazinylindole DPI 201-106.

Abstract: 1. External Ca2+ block of Na+ channels was studied by a gigaohm-seal patch clamp technique in single cardiac ventricular cells from guinea-pig. Single-channel currents were recorded from cell-attached patches. 2. Increasing external Ca2+ concentrations in the patch pipette from 0.1 to 20 mM reduced the single-channel conductance of normal Na+ channels from 27 to 14 pS without causing flickering (obtained from linear regression, eight patches). 3. Exposed to external Ca2+ concentrations of 20 mM, the single-channel currents decreased at potentials negative to -60 mV in spite of an increased driving force for inward Na+ currents. 4. An external concentration of 35 mM-Mg2+, which is supposed to exert a screening of surface charges nearly equal to that of 20 mM-Ca2+ (Hille, Woodhull & Shapiro, 1975), reduced the single-Na+-channel conductance only from 26 (1 mM-Mg2+) to 20 pS (linear regression, eight patches). A weaker voltage-dependent block at potentials negative to -50 mV was observed in 35 mM-Mg2+ than in 20 mM-Ca2+. Therefore, surface charge effects cannot explain the obvious reduction of the conductance of single Na+ channels found when the external Ca2+ concentration was increased. 5. Single Na+-channel currents increased with an increase in the external Na+ concentration [( Na+]o) but showed saturation. The Na+o-single-channel current relationship could be described by i = imax/(1 + kd/[Na+]o) with imax = 5.4 pA and kd = 359 mM (seventeen patches). 6. The mean open time of Na+ channels varied between 0.18 and 0.59 ms (potentials between -80 and -20 mV). No significant changes in the mean open time could be obtained when Ca2+ was varied between 0.1 and 20 mM. 7. The piperazinylindole compound DPI 201-106 was used as a tool to prolong the open time of single Na+ channels. If the external Ca2+ concentration was increased from 0.1 to 20 mM the currents through the modified channels were reduced. The reduction of single-channel currents was accentuated at potentials negative to -60 mV (20 mM-Ca2+) similar to the control channels. 8. In contrast to non-modified Na+ channels, the mean open time of DPI 201-106-modified channels proved extremely voltage and Ca2+ dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of salts on the covalent immobilization of proteins to modified copolymers of 2-hydroxyethyl methacrylate with ethylene dimethacrylate.

Abstract: In the study of the covalent immobilization of aminoacylase, thermitase, pepsin, trypsin, chymotrypsin, elastase, subtilisin, penicillinamidohydrolase, carboxypeptidase A, cystathionine-beta-synthase, and anticathepsin D-IgG to copolymers of 2-hydroxyethyl methacrylate and ethylene dimethacrylate (Separon HEMA) containing epoxy groups a marked influence of added salts on the immobilization efficiency was observed. Yields in covalently bound active enzymes were dependent on the concentrations and type of ions added, which can be arranged according to the Hofmeister series. At a distinct concentration, the salting-out ions cause a protein-matrix hydrophobic interaction which is a prerequisite for the covalent bond formation.

Properties of an early outward current in single cells of the mouse ventricle.

Abstract: Single ventricular myocytes of adult mice were prepared by enzymatic dissociation for voltage clamp experiments with the one suction pipette dialysis method. After blocking the Na current by 10(-4) mol/l TTX early outward currents (IEO) with incomplete inactivation could be elicited by clamping from -50 mV to test potentials (VT) positive to -30 mV. Interfering Ca currents were very small (less than 0.6 nA at VT = 0 mV). The approximation of IEO by the q4r-model showed a pronounced decrease in the time constant of activation (tau q) to more positive potentials. At 50 ms test pulses the time course of the incomplete inactivation could be described by two exponentials and a constant. The time constant of the fast exponential (tau r1) showed a slight decline towards more positive test potentials (8.1 +/- 1.0 ms at -10 mV; 5.8 +/- 1.2 ms at +50 mV, mean +/- SD, n = 5) whereas the time constant of the slow exponential (tau r2) was voltage independent (41.1 +/- 7.9 ms, mean +/- SD, n = 5). The contributions of the fast exponential and the pedestal increased towards positive test potentials. The Q10 value for the time constants of activation and fast inactivation was 2.36 +/- 0.19 and 2.51 +/- 0.09 (mean +/- SD, n = 3), respectively. After an initial delay the recovery of IEO at a recovery potential of -50 mV could be fitted monoexponentially with a time constant of 16.3 +/- 2.9 ms (mean +/- SD, n = 3). The time course of the onset of inactivation determined with the double pulse protocol was slower than the decay at the same potential, and could be described as sum of a fast (tau = 18.4 +/- 6.0 ms) and a slow (tau = 62.1 +/- 19.9ms, mean +/- SD, n = 3) exponential. IEO could be blocked completely by 1 mmol/l 4-aminopyridine at potentials up to +20 mV. Stronger depolarizations had an unblocking effect.

The relationship between phosphate absorption and root length in nine wheat cultivars

Abstract: Because the diffusion coefficients of potassium and especially of phosphate ions in the soil are very small (Barber, 1974) the uptake of these nutrients is extensively dependent on the concentration gradient and the diffusion conditions (e.g. water content) of the soils (Romer and Schilling, 1987). For this reason the nutrients mentioned can only be exploited from a small soil cylinder around the roots (Jungk, 1984). Therefore plant species with a large root system like grasses are superior to others e.g. leguminous plants with regard to phosphate uptake (Steffen, 1984).

Dipeptidylpeptidase IV--inactivation with N-peptidyl-O-aroyl hydroxylamines.

Abstract: Eleven N-peptidyl-o-aroyl hydroxylamines have been synthesized and their hydrolytic stability, acidity and properties during reaction with dipeptidyl peptidase IV (EC 34145) investigated N-peptidyl-o-(4-nitrobenzoyl) hydroxylamines act as irreversible inhibitors of serine proteases1 The serine enzyme, dipeptidyl peptidase IV (DP IV), is inactivated by substrate analog derivatives of this class by a suicide inactivation mechanism During the enzymic reaction of DP IV with the suicide substrates most molecules are hydrolyzed but some irreversibly inactivate the target enzyme In contrast to porcine pancreatic elastase and thermitase, DP IV exhibits a high ratio for hydrolysis of the compounds versus inhibition during their interaction with the enzyme Variation of the leaving aroyl residue lowers this ratio Variation of the substrate analog peptide moieties of the DP IV-inhibitors increases their ability to inhibit the enzyme to a remarkable extent Possible reaction pathways are discussed

Structure and Dilution of Mesogenic Side Chains in Liquid Crystalline Polysiloxanes

Abstract: The structure of the smectic phases in four series of homo- and copolymers based on dimethylsiloxane chains with a definite variation of the concentration of the paired mesogenic side chains has been investigated by means of X-ray methods. The dilution of the mesogenic moiety was achieved by insertion of additional dimethylsiloxane segments. A nearly linear dependence of the layer spacings on the dilution has been found. A model of the structure is proposed which consists of two sublayers one of which contains the irregularly arranged main chain whereas the other one is formed by the side chains.

A polypeptide growth inhibitor isolated from lactating bovine mammary gland (MDGI) is a lipid-carrying protein.

Abstract: Mammary-derived growth inhibitor (MDGI), a polypeptide growth inhibitor isolated from lactating bovine mammary tissue, previously shown to have extensive sequence homology with fatty acid-binding proteins, was demonstrated to meet the criteria of a fatty acid-binding protein. The protein was found to bind [3H]palmitic acid in a saturable manner and to be complexed with endogeneous free fatty acids. [3H]palmitic acid, when bound to the protein, was more rapidly taken up by the target cells (human mammary carcinoma cells [MaTu]) than was free [3H]palmitic acid, suggesting a lipid carrier function for the inhibitor. It is suggested that the fatty acid-binding properties of MDGI may relate to its ability to inhibit cell growth in vitro and to regulate other cellular functions.

Cytogenetic analysis of the echinoid (ed), dumpy (dp) and clot (cl) region in Drosophila melanogaster

Abstract: The chromosomal region surrounding the ed, dp and cl genes has been studied cytogenetically (24–26 on 2L chromosome). It contains three Minutes and a haplo-sterile function. For isolation of deficiencies and mutations these haplo-insufficient functions were covered by an insertional translocation of 24D4-25F2 into the X chromosome, or by tandem duplications. 112 lethal and visible mutations induced by EMS and X-rays have been localized by deficiency mapping to 20 subregions. They specify 42 loci in a 48 band interval consistent with the notion that most of the bands encode a single lethal function. The dp, DTS, tkv and suppressor/enhancer loci for position-effect variegation were studied in detail. A dominant suppressor function was localized within the structural part of the dp complex. New non-conditional lethals have been isolated for the DTS locus. Complementation analysis with the previously identified dominant heat-sensitive alleles places the site for heat sensitivity in the middle of the locus. Two haplo-abnormal enhancers of position-effect variegation were localized in the region 25F2–26A1. A triplo-abnormal suppressor function maps to 26B2–5; 26B9. The dose-dependent functions of these loci were studied by the use of deficiencies and duplications.

Liquid crystalline swallow-tailed compounds (II) dielectric relaxation†

Abstract: Dielectric investigations in the kHz-range on swallow-tailed liquid crystals show a strong decrease of the dielectric constant as well as of the dielectric loss parallel to the nematic director with decreasing temperature. In the perpendicular direction no strong anomaly has been observed. By consideration of X-ray data of the SA phase the dielectric results can be interpreted by the dipole-dipole interaction which is forced by the anisotropy of repulsive forces of the respective molecules. Dielektrische Untersuchungen im kHz-Bereich an schwalbenschwanzartigen Flussigkristallen zeigten sowohl einen starken Abfall der Dielektrizitatskonstanten als auch des Verlustes parallel zum nematischer Direktor mit sinkender Temperatur. In senkrechter Richtung wurden keine starkeren Anomalien beobachtet. Unter Berucksichtigung von Rontgenwerten in der SA-Phase konnen die dielektrischen Ergebnisse durch die Dipol-Dipol-Wechselwirkung erklart werden, die durch die Anisotropie der repulsiven Krafte der entsprechenden Molekule verstarkt wird.

Strukturelle Eigenschaften der Dicyanamid‐ und Tricyanmethanid‐Komplexe von Kupfer(II), Nickel(II) und Kobalt(II) mit Liganden des Pyrazol‐Typs Nukleophile Additionsreaktionen in einigen der untersuchten Systeme

Abstract: Aus den Systemen MIIX−L, mit M = Cu, Ni, Co; X = N(CN)2, C(CN)3; L = Pyrazol, 3(5)-Methylpyrazol, 3,5-Dimethylpyrazol, 3,4,5-Trimethylpyrazol, Indazol, wurde eine Reihe neuer Komplexe des Typs MX2L2 sowie auch die Verbindungen Cu{Indazol-N(CN)2}2 und Ni{Pyrazol-N(CN)2}2 isoliert. Die letztgenannten Komplexe enthalten anionische Chelat-Liganden, die durch nukleophile Addition des Pyrazol-Liganden an koordinativ gebundenes Dicyanamid entstanden sind. Diese Chelat-Liganden enthaltenden Komplexe bilden mit den entsprechenden Dicyanamid-Komplexen Coligandenisomeren-Paare. IR-, Elektronen oder auch ESR-Spektren zeigen an, das samtliche Komplexe Koordinationspolymere darstellen, mit einer Koordinationszahl sechs der Zentralatome. Diese wird ermoglicht durch eine in Bruckenfunktion wirkende Zweizahnigkeit der Dicyanamid- bzw. Tricyanmethanid-Liganden, oder uber eine ebenfalls in Bruckenfunktion wirkende Ligator-Funktion des Stickstoffs freier CN-Gruppen des Chelat-Liganden. Structure Properties of Dicyanamide and Tricyanmethanide Complexes of Copper(II), Nickel(II), and Cobalt(II) with Ligands of Pyrazole Type — Nucleophilic Addition Reaction in Some of the Studied Systems From the MIIX−L systems with M = Cu, Ni, Co; X = N(CN)2, C(CN)3; L = pyrazole, 3(5)-methylpyrazole, 3,5-dimethylpyrazole, 3,4,5-trimethylpyrazole, indazole, a series of new compounds of the type MX2L2, as well as the compounds Cu{indazole-N(CN)2}2 and Ni{pyrazole-N(CN)2}2 were isolated. The later compounds contain anionic chelate ligands which are formed by nucleophilic addition of the pyrazole ligand to dicyanamide bonded in the coordination sphere. These complexes of chelate ligands give with the corresponding dicyanamide complexes pairs of coligand isomers. The IR, electronic, or ESR spectra indicate that all complexes are polymeric in character, their central atoms showing a six coordination. This is made possible through bridging bidentate dicyanamide or tricyanmethanide ligands, and likewise through ligand function of the nitrogens from free CN groups of the chelate ligands participating also in some bridging function.

A general model of metabolite kinetics following intravenous and oral administration of the parent drug.

Abstract: A model of metabolite pharmacokinetics is developed in terms of residence time distributions and derived non-compartmental measures. It provides quantitative insight into factors determining the concentration-time curve of metabolite following intravenous and oral administration of the precursor drug. The AUCs and higher curve moments (mean residence times and relative dispersions) are calculated/predicted and their dependence on mean absorption time, fraction of first-pass metabolism and intrinsic disposition residence times of the parent drug and metabolite, respectively, is discussed. An AUC-based method for the determination of the first-pass effect is proposed which is not influenced by drug absorption. The approach is valid for linear pharmacokinetic systems exhibiting hepatic and renal elimination of the precursor drug; it is not restricted to specific compartmental models. Limitations of previous concepts of metabolite kinetics are defined. Criteria are presented for the appearance of concave metabolite curves in a semi-logarithmic scale.