Showing papers by "University of Hamburg published in 1984"

Single base deletion in the vasopressin gene is the cause of diabetes insipidus in Brattleboro rats

Abstract: In rats with hereditary hypothalamic diabetes insipidus (Brattleboro rats) the gene for the vasopressin precursor lacks a single G residue in the protein-coding region. The mutation gives rise to an open reading frame predicting a hormone precursor having a different C-terminus.

New likelihood test methods for change detection in image sequences

Abstract: Modeling the image as a piecewise linear gray-value function of the pixel coordinates considerably improved a change detection test based previously on a piecewise constant gray-value function. These results encouraged investigations into modeling the picture as a mosaic of patches where the gray-value function within each patch is described as a second-order bivariate polynomial of the pixel coordinates. Such a more appropriate model allowed the assumption to be made that the remaining gray-value variation within each patch can be attributed to noise related to the sensing and digitizing devices, independent of the individual image frames in a sequence. This assumption made it possible to relate the likelihood test for change detection to well-known statistical tests ( t test, F test), facilitating the determination of threshold values related to a priori confidence limits.

Seasonality in the fluxes of sugars, amino acids, and amino sugars to the deep ocean: Sargasso sea

Abstract: The fluxes of sugars, amino acids, and amino sugars as released by acid hydrolysis were determined in the < 37-μm fraction of samples collected during successive two-month sediment trap deployments in the deep Sargasso Sea (3200 ± 100 m) from April 1978 to December 1981. All fluxes varied seasonally and in phase with the flux of the < 37-μm fraction, which has been shown to vary in phase with primary productivity in the surface layers. During the investigation the fluxes were in the range of 0.03 to 1.7 mg m−2 d−1. They contributed 13 to 34% of the measured organic carbon, and 30 to 53% of the measured total nitrogen could be accounted for by amino acids and amino sugars. The relative abundances of sugars and amino acids were, in general, similar to those reported for mineralized tissues of carbonate and silica producers and the cell walls of non-biomeneralizing organisms. However, the amounts of non-protein amino acids, i.e., β-alanine and γ-aminobutyric acid, of aspartic and glutamic acids, and of amino sugars relative to total amino acids varied seasonally. Relative abundances of these compounds appear to indicate the nature and source of organic matter arriving at the sediment trap.

Responses of human cutaneous afferents to CO2 laser stimuli causing pain.

Abstract: Microelectroneurographic studies in man allow the comparison of stimulus induced activity in the single peripheral nerve unit with the subject's ratings of sensation. Relationships between stimulus intensity, single unit discharges, and pain ratings were investigated using a CO2 laser stimulator which delivers radiant heat pulses of 50 ms duration. Recordings were performed percutaneously from the radial nerve at the wrist. Receptor types were identified by their response to different stimulus modalities and by their reaction delay to electrical test stimuli within the receptive field. Receptive fields of identified units were stimulated with randomised series of different radiant heat intensities between half and double the individual pain threshold (5 to 20 W; stimulation area 64 mm2). The largest receptor class observed to be activated by CO2 laser stimuli were polymodal C-nociceptors. None of them was spontaneously active. High discharge rates up to 75/s were not necessarily associated with pain but, if pain was felt, the impulse trains usually lasted for more than 60 ms. Inter-spike intervals were distributed over a wide range between 8 and 145 ms with a peak at about 25 ms. This peak was only slightly shifted by increasing the stimulus intensity. Higher correlations were found between the number of spikes and stimulus intensity. Measures of Signal Detection Theory indicated that the single unit discharges discriminated stimulus intensities better than the subjects' ratings. These findings underline the importance of temporal summation in the processing of C-fibre input with a considerable loss of information in the nociceptive system.

Jet Production and Fragmentation in E+e- Annihilation at 12-43 Gev

Abstract: We present the general properties of jets produced bye+e− annihilation. Their production and fragmentation characteristics have been studied with charged particles for c.m. energies between 12 and 43 GeV. In this energy rangee+e− annihilation into hadrons is dominated by pair production of the five quarksu, d, s, c andb. In addition, hard gluon bremsstrahlung effects which are invisible at low energies become prominent at the high energies. The observed multiplicity distributions deviate from a Poisson distribution. The multiplicity distributions for the overall event as well as for each event hemisphere satisfy KNO scaling to within ∼20%. The distributions ofxp=2p/W are presented; scale breaking is observed at the level of 25%. The quantityxpdδ/dxp is compared with multigluon emission calculations which predict a Gaussian distribution in terms of ln(1/x). The observed energy dependence of the maximum of the distributions is in qualitative agreement with the calculations. Particle production is analysed with respect to the jet axis and longitudinal and transverse momentum spectra are presented. The angular distribution of the jet axis strongly supports the idea of predominant spin 1/2 quark pair production. The particle distributions with respect to the event plane show clearly the growing importance of planar events with increasing c.m. energies. They also exclude the presence of heavy quark production,e+e−→Q\(\bar Q\) for quark masses up to 5

Seasonality in the fluxes of sugars, amino acids, and amino sugars to the deep ocean: Panama basin

Abstract: Time-series sediment traps were deployed for an entire year at depths of 890, 2590, and 3560 m at a station in the Panama Basin during 1980. Fluxes of sugars, amino acids, and amino sugars varied seasonally at each depth. Two peak fluxes were observed: one in February–March, the other in June–July. The peaks were associated with a high productivity period by regional upwelling and an unusual coccolithophorid bloom. There were significant differences in the distributions of sugars and amino acids associated with the fluxes. The peak flux of June/July was characterized by high amounts of arabinose and ribose within the sugar, and high amounts of aspartic acid in the amino acid fractions. The differences were observed at all three depths simultaneously, indicating rapid vertical transport without significant dissolution or decomposition. The observed pattern indicates the utility of specific compounds such as sugars and amino acids as tracers of source materials in the marine environment.

Membrane-bound nitrite oxidoreductase of Nitrobacter: evidence for a nitrate reductase system

Abstract: Nitrite oxidoreductase, the essential enzyme complex of nitrite oxidizing membranes, was isolated from cells of the nitrifying bacterium Nitrobacter hamburgensis. The enzyme system was solubilized and purified in the presence of 0.25% sodium deoxycholate. Nitrite oxidoreductase oxidized nitrite to nitrate in the presence of ferricyanide. The pH optimum was 8.0, and the apparent Km value for nitrite amounted to 3.6 mM. With reduced methyl-and benzylviologen nitrite oxidoreductase exhibited nitrate reductase activity with an apparent Km value of 0.9 mM for nitrate. NADH was also a suitable electron donor for nitrate reduction. The pH optimum was 7.0.

Concrete corrosion in the Hamburg Sewer system

Abstract: In the sewer network of Hamburg extensive biogenic sulfuric acid corrosion was noted”; A field study indicated thiobacilli of the species Thiobacillus neapolitarius, T. intermedius, T. novellus, and T. thio‐oxidans. A positive correlation between the cell numbers of T. thio‐oxidans and the grade of corrosion was noted. As sources of sulfur the volatile compounds hydrogen sulfide, sulfite, methylmercaptane, dimethylsulfide, and dithiabutane are possible. Biogenic concrete corrosion was simulated in a strictly controlled H2S breeding chamber. Differences among various concrete types were reproducibly demonstrated.

On Quantum Field Theory in Gravitational Background

Abstract: We discuss quantum fields on Riemannian space-time. A principle of local definiteness is introduced which is needed beyond equations of motion and commutation relations to fix the theory uniquely. It also allows us to formulate local stability. In application to a region with a time-like Killing vector field and horizons it yields the value of the Hawking temperature. The concept of vacuum and particles in a non-stationary metric is treated in the example of the Robertson-Walker metric and some remarks on detectors in non-inertial motion are added.

A geological study of lake van, Eastern Turkey

Abstract: Lake Van is a lake with a volume of 607 km3 and a maximum depth of 451 m in a tectonically active zone in eastern Anatolia. It may be divided into three physiographic provinces: lacustrine shelf, sublacustrine slope and lake basin. The shelf is largely made up of submerged fluvial valleys and alluvial plains, as evidenced by the local occurrence of karst-like topography, buried, leveed river valleys and sediment wedges interpretable as relict deltas. The shelf and basinal deposits are characterized by an alternating succession of well-stratified and chaotically reflecting layers consisting of turbidites and slump deposits respectively. This thick sequence of unconsolidated to consolidated sediments is underlain by a Paleozoic metamorphic or Upper Cretaceous limestone basement.

Effects of α-adrenoceptor stimulation with phenylephrine in the presence of propranolol on force of contraction, slow inward current and cyclic AMP content in the bovine heart

Abstract: The mechanism of the cyclic AMP-independent positive inotropic effect of cardiac alpha-adrenoceptor stimulation was studied by analyzing the effects of phenylephrine on force of contraction, calcium-dependent slow action potentials and the slow inward current (Isi) in bovine ventricular trabeculae. The preparations were electrically driven at 0.3 Hz in the presence of propranolol 1 mumol 1(-1). Phenylephrine increased the force of contraction in a concentration-dependent manner (maximum about 200% of control at 30 mumol 1(-1). The effect was surmountably antagonized by phentolamine. The positive inotropic effect of phenylephrine was accompanied by a concentration-dependent increase in time to peak force and occurred without any detectable increase in cyclic adenosine 3',5'-monophosphate (cyclic AMP) levels. The positive inotropic effect of phenylephrine was accompanied by an increase in action potential duration both at 20% and 90% repolarization. Calcium-dependent slow action potentials were also prolonged by phenylephrine and there was a distinct increase in the maximal rate of depolarization (dV/dtmax) of these slow potentials. These effects were also completely reversible on washing and surmountably blocked by phentolamine. However, the increase in dV/dtmax was smaller than that of isoprenaline in concentrations producing similar inotropic effects. Voltage-clamp experiments with the single sucrose-gap method showed that the phenylephrine-induced increase in force of contraction was associated not only with an increase in peak slow calcium inward current, Isi max, but also with a delay in the inactivation of Isi. Outward currents were not detectably altered by phenylephrine. It is concluded that the alpha-adrenoceptor mediated, cyclic AMP-independent positive inotropic effects of phenylephrine in bovine cardiac muscle are associated with an increase in slow inward current. Additionally, the amount of calcium influx during excitation is probably increased by a delay in the inactivation of Isi. Both effects can explain the phenylephrine-produced prolongation of the action potential, and probably contribute to the positive inotropic effect of alpha-adrenoceptor stimulation. However, as the effect on dV/dtmax is smaller than that of isoprenaline, other (still unknown) mechanisms may also be involved.

Mass Transfer from Solid Material in Gas Extraction

Abstract: Etude du transfert de matiere lors de l'extraction par gaz supercritique, sur l'exemple de grains de cafe et de graines de colza

Diazadienes as Controlling Ligands in Catalysis, 51). Synthesis of Chiral Diazadienes R* – N = CR' – CR' = N – R*

Abstract: The condensation of glyoxal (as hydrate) or 2,3-butanedione with primary amines is, in principle, a simple reaction. Unfortunately, aliphatic amines with secondary or tertiary α-carbons often give unwanted addition products. Under special reaction conditions the desired diimines (diazadienes (dad): R* – N = CR' – CR' = N – R*, R' = H, CH3) 4, and 6 – 8 are obtained from (R-1-phenyl-ethylamine (1) and (1S,2S,3S,5R)-3-(aminomethyl)pinane (2). Depending on the dione, a morpholinomorpholine 9 and a bioxazolidine 10 are formed from (S)-2-amino-1-butanol (3), which are bound by electron-rich metals in their isomeric dad form ((dad)Mo(CO)411 and 12). The acyclic dad structure is stabilized by O-silylation (14, 15). The (dad)iron(0) catalyzed dimerization of butadiene with these controlling ligands to 4-vinyl-1-cyclohexene occurs with an enantiomeric excess up to 16%. Diazadiene als Steuerliganden in der Katalyse, 51). Synthese chiraler Diazadiene R* – N = CR' – CR' = N – R* Die im Prinzip einfache Kondensationsreaktion von Glyoxal (als Hydrat) und 2,3-Butandion mit primaren Aminen fuhrt leider bei aliphatischen Aminen mit tertiarem bzw. sekundarem α-Kohlenstoff oftmals zu unerwunschten Additionsprodukten. Unter speziellen Synthesebedingungen konnen mit (R)-1-Phenylethylamin (1) und (1S,2S,3S,5R)-3-(Aminomethyl)pinan die gewunschten Diimine (Diazadiene (dad): R* – N = CR' – CR' = N – R*, R' = H, CH3) 4, 6 – 8 erhalten werden. Aus (S)-2-Amino-1-butanol (3) werden je nach Dion-Komponente ein Morpholinomorpholin 9 bzw. ein Bioxazolidin 10 gebildet, die von elektronenreichen Metallen in ihrer isomeren Form als Diazadiene gebunden werden ((dad)Mo(CO)411 und 12). Die offenkettige dad-Form ist durch O-Silylierung (14, 15) stabilisierbar. Die (dad)Eisen(0)-katalysierte Dimerisierung von Butadien zu 4-Vinyl-1-cyclohexen mit diesen dad-Liganden ergibt Enantiomerenuberschusse e.e. bis zu 16%.

Organization and morphogenesis of the human seminiferous epithelium

Abstract: The various types of human primary spermatocytes were classified by means of morphological and morphometrical studies Based on this classification, the topographic arrangement of the spermatocyte populations in the longitudinal course of seminiferous tubules was determined This analysis revealed human spermatogenesis be to subjected to a complex local plan of organization, which is based upon the geometry of spirals The centers of gravity of spermatocyte populations of subsequent degrees of differentiation are arranged on he lices that are contracted conically to the lumen of the seminiferous tubule On these helices the centers of gravity of the populations diverge continuously 1738°+/-324° Populations of the same degrees of development are arranged on helices with constant diameters On these helices the centers of gravity of the populations diverge continuously 1426°+/-142° The present results lead to new aspects of the kinetics and morphogenesis of the seminiferous epithelium, which can be integrated into a comprehensive biological concept

Optical flow

Abstract: A large number of contributions to this workshop is concerned with computing or making use of optical flow . This i s the term now commonly used for an intermediate representation of time-varying imagery where each pixel is assigned a velocity vector describing its temporal displacement in th e image plane or—for human vision-in the retinal field . Optical flow can be consciously experienced by human observers (e .g . when travelling in a car) and has early been recognized a s a valuable source of information pertaining to the motion an d 3D characteristics of a scene (GIBSON 50) . Thorough quantitative analyses, however, have only become available during the last five years, when an increasing number of vision researchers turned to motion problems . As can be seen fro m this workshop, interesting results on how to exploit optica l flow are still being uncovered . Before making use of optical flow it must be computed — unfortunately . As it turns out, no computational theory has yet been offered which promises satisfactory results for unrestricted real-world images . Nevertheless, considerable progres s has been made in certain restricted situations . This is als o documented by several contributions to this workshop . hi thi s introductory survey I shall try to point out the major differences in the approaches taken so far. Fig . 1 gives a rough sketch of the representations and th e processing connected with optical flow . Much of the variety o f the research contributions is due to certain assumptions abou t the visual world . These will be discussed in the following sec tion . The visual world is projected yielding intensity arrays from which optical flow computation per se proceeds . Thre e rather distinct directions of processing have been proposed . A s a first possibility, optical flow is directly computed from th e intensity array . The result is usually a dense flow field . Alternately, descriptive elements like prominent points or edges may be computed first . Points usually give rise to a sparse flo w field after correspondence is established . Edges lead to a quit e different flow compentation clue to the remaining degree of freedom . In section 3 these distinctions are elaborated in som e more detail . Finally, I shall briefly review ways of extractin g useful information from optical flow .

Thyroid hormone action on intermediary metabolism. Part I: respiration, thermogenesis and carbohydrate metabolism.

Abstract: The effect of thyroid hormones on mitochondrial respiration are summarized: T3 directly stimulates mitochondrial respiration and the synthesis of adenosine 5′-triphosphate (ATP). Cytosolic ATP availability is increased by a thyroid hormone-induced increase in adenine nucleotide translocation across the mitochondrial membrane; the steady state ATP concentration and the cytosolic ATP/adenosine 5′-diphosphate (ADP) ratio is even decreased in hyperthyroid tissues because of the simultaneous stimulation of the synthesis and consumption of ATP. With regard to the thyroid hormone-induced energy wasting processes, heart work, intra- and interorgan futile cycling and Na+/K+-ATPase are involved to varying degrees. As a consequence of the thyroid hormone-induced hydrolysis of ATP, thermogenesis is increased in hyper- and decreased in hypothyroidism. Despite an increased rate of glucose utilization, clinical and experimental hyperthyroidism is often characterized by an abnormal oral glucose tolerance test. This finding is due to the thyroid hormone-induced increase in intestinal glucose absorption as well as the still enhanced endogenous glucose production in the liver. Hypothyroid patients show a reduced glucose tolerance test because of a decrease in intestinal glucose absorption and a sometimes reduced glucose turnover. The thyroid hormone-induced alterations in glucose metabolism are most probably not due to alterations in serum insulin levels and/or to a peripheral insulin resistance at the receptor level.

Spawning periodicity and habitat of the palolo worm Eunice viridis (Polychaeta: Eunicidae) in the Samoan Islands

Abstract: The relationship between the phase of the moon and the emergence of the epitokous segments of the palolo worm Eunice viridis Gray has been known to the natives of the Samoan Islands for centuries. They predict the date and time of day when the emergence occurs so that they can be ready to catch the worms. This phenomenon is one of the best known examples of lunar periodicity. It was first described scientifically at the end of the last century. My own investigations concern the occurrence of the worms in the reef, in which they gnaw long tunnels through the massive blocks of coral limestone at levels characterized by the occurrence of symbiotic algae. Apparently the algae are the main sources of nutrition for the worms. The casting off of the epitokous segments occurs at the third quarter of the moon in October or November. An analysis of known dates on which the swarms of worms have appeared permitted a precise method of prediction to be formulated. The causality of this periodicity is discussed.