Showing papers by "Free University of Berlin published in 1986"

A routine method for the establishment of permanent growing lymphoblastoid cell lines

Abstract: Permanent lymphoblastoid cell lines are of great practical value in human clinical and experimental genetics. A detailed protocol for routine use is given for the establishment of lymphoblastoid lines from peripheral blood using Esptein-Barr virus and the immunosuppressivum Cyclosporin A. In addition, the biologic basis of this transformation system is briefly summarized.

An Update of the Observed Quasi-Biennial Oscillation of the Stratospheric Winds over the Tropics

Abstract: A survey of the zonal wind in the stratosphere near the equator is made for the 32-year period 1953–84. The monthly mean zonal wind components have been calculated from daily observations at Canton Island, Gan, and Singapore at levels between 70 and 10 mb. A frequency distribution of the zonal wind at 30 mb has been derived from these data and a long-term mean quasi-biennial oscillation (QBO) has been constructed from the 14 complete cycles included in the period.

DNA conformation is determined by economics in the hydration of phosphate groups

Abstract: Mixed sequence DNA can exist in two right-handed and one left-handed double helical conformations--A, B and Z. Under conditions of high water activity the B conformation prevails. If the water activity is reduced on addition of salt or organic solvents, transformation occurs to A-DNA or, in DNAs with alternating purine-pyrimidine sequences, to the left-handed Z-DNA. In crystal structure analyses of oligonucleotides, the free oxygen atoms of adjacent phosphate groups along the polynucleotide chain in B-DNA are found at least 6.6 A apart and individually hydrated whereas they are as close as 5.3 A in A-DNA and 4.4 A in Z-DNA, and bridged by water molecules. We suggest that this more economical hydration in A- and Z-DNA compared with B-DNA is the underlying cause of B----A and B----Z transitions.

Estimating the Dimensions of Weather and Climate Attractors

Abstract: The dimensions of attractors are estimated from phase space trajectories of observed weather and climate variables (local surface pressure and relative sunshine duration, zonal wave amplitude; a δ18O-record). They provide primary information for descriptions of properties of the attractors of dynamical systems and give a lower limit to the number of the essential variables necessary to model the dynamics. These estimates are based on distance distributions of pairs of points on the single variable trajectory evolving in phase spaces which embed the attractor. One observes a low fractal dimensionality between three and four for the weather attractor, if interannual variability and seasonal changes are eliminated. The physical interpretation is based on the three dominating scales of cyclones, cyclone families and index-cycle; the irregularity of the flow and strong dependence on initial conditions amount for the fractal value. The climate variable also reveals a low dimensionality (between four an...

Size distributions of vesicles: the role of the effective rigidity of membranes

Abstract: On calcule la distribution des tailles des vesicules spheriques et en particulier la maniere dont la rigidite effective depend de la taille des couches bi-moleculaires. Pour les vesicules spheriques on montre que cette rigidite decroit comme le logarithme de la taille. Pour les petites tailles, on construit une section de la distribution a partir des termes non hookeens de l'elasticite de courbure

IgE-mediated degranulation of mast cells does not require opening of ion channels

Abstract: Rat peritoneal mast cells respond to antigenic stimulation by releasing histamine through exocytosis. The dynamics of exocytosis can be investigated by dialysing single cells with patch pipettes using the whole-cell recording configuration of the patch-clamp technique1,2. However, dialysed cells fail to respond to external stimuli such as compound 48/80 or antigens, suggesting that essential cytoplasmic components have been washed out. We have developed a new patch-clamp configuration in which the patch under the pipette tip is not disrupted but instead permeabilized, preventing the diffusion of large molecules out of the cell. In this configuration the cell responds to external stimulation, and the capacitance as well as the conductance of the cell membrane can be recorded during degranulation. On antigenic stimulation, the cell capacitance (proportional to plasma membrane area), after an initial delay, increases by a factor of about 3. This increase in capacitance is often preceded by a transient increase in conductance. Agents that block Ca-activated channels inhibit this conductance change without affecting the amplitude and time course of degranulation. We therefore conclude that, in contrast to excitable secretory cells such as chromaffin cells2, mast cells do not use ion channels in stimulus-secretion coupling.

Spectral sensitivity of photoreceptors in insect compound eyes: Comparison of species and methods

Abstract: Three different methods were used to determine the spectral sensitivity of retinula cells in the compound eyes of three species of hymenopteran insects (Apis mellifera, Melipona quadrifasciata, Osmia rufa). The conventional flash method gives the least reliable results. Sensitivity is extremely sensitive to small fluctuations of the resting potential and long lasting changes induced by preceding test flashes. The ramp method, which speeds up a spectral scan to about 1 min and keeps effective illumination constant at every flash, determines S(λ) much more reliably. The best results are obtained with the spectral scan method, which provides the experimenter with aS(λ) function of high spectral resolution within 20 s. Using this method we demonstrate that the high observed variability inS(λ) of individual receptors is the result of the inadequacy of the flash method, which was the only method used in earlier studies. Double microelectrode experiments and variations of the stimulus conditions reveal that field potentials and return flow of electric current produced by activated neighboring cells have no effect in the bee eye. We conclude that the model of Shaw (1975, 1981) of current flow in the locust and fly eye does not apply to the bee eye. Very rare recordings (about 1%) of UV receptors with hyperpolarizing responses to long wavelength light are interpreted as having a synaptic inhibitory connection to green receptors. The improvement of spectral measurements of single receptors allows us for the first time to model the spectral input to a color-coding network with great precision.

Encapsulation in Arthropods

Abstract: Encapsulation is the common type of defense reaction in arthropods against invading pathogens and parasites, introduced foreign bodies, or injected particulate materials. Phagocytosis predominates when the haemocoel is exposed to small numbers of foreign particles [28]. Further immune capacity of arthropods is based on the presence or neosynthesis of humoral substances, such as lysozyme, cecropins, attacins (see Chap. 6), and other compounds with antibiotic efficiency [13].

Changes in intracranial pressure associated with extradural anaesthesia

Abstract: The intracranial pressure (ICP) response to the lumbar extradural injection of bupivacaine hydrochloride was measured in two patients on a total of 29 occasions. In the first patient, mean ICP increased from an average figure of 18.8 mm Hg to 39.5 mm Hg after the injection of 10 ml of solution. This increase was maintained for an average of 4.5 min. Both the magnitude and the duration of the increase were less when 5 ml was injected. The second patient had a normal baseline ICP, but the injection of bupivacaine 10ml produced an increase from a mean of 9. 3 mm Hg to 15. 6 mm Hg. Injection of the same volumes of physiological saline in the second patient induced increases in ICP similar to those obtained with bupivacaine. There was a good correlation between baseline ICP and the increase produced by the extradural injection. It is concluded that extradural anaesthesia must be used with extreme caution in patients with reduced intracranial compliance, and should not be used at all in a patient with intracranial hypertension or a space-occupying lesion.

Weak acids may act as teratogens by accumulating in the basic milieu of the early mammalian embryo.

Abstract: Among the eleven drugs or chemicals which are well-documented human teratogens, eight (or their main metabolites) are weak acids whereas none is a weak base. Moreover, 23 out of 32 acids tested have been found to be teratogenic in at least one animal species. The acidic property of drugs may therefore be an important determinant of teratogenicity. We demonstrate here that the intracellular pH (pHi) of the mouse and rat embryo is higher than that of maternal plasma, as determined by the relative accumulation of dimethadione. The antiepileptic drug valproic acid and its pharmacologically active unsaturated metabolite accumulate in embryonic tissue to higher concentrations than in maternal plasma, whereas the essentially neutral amide of valproic acid (valpromide) or ethosuximide do not accumulate in the embryo; we further demonstrate in the rat that the pHi of the embryo decreases with advancing gestation; in general agreement with the pH partition hypothesis, the exposure of the embryo to valproic acid also decreases significantly during that period. Furthermore, the amides of two weak acid teratogens, valpromide and methoxyacetamide, and the imide ethosuximide, are much less teratogenic than their acid counterparts. Our results suggest that weakly acidic drugs, by virtue of their physico-chemical nature, accumulate in the early embryo with its relatively high pHi.

Photo‐sieving: A method for grain‐size analysis of coarse‐grained, unconsolidated bedding surfaces

Abstract: The photo-sieving method enables the grain-size analysis of particles > 10 mm from unconsolidated openwork bedding surfaces. The accuracy is equal to the machine-sieving method. The sediment surface is photographed in the field using a camera stand. The enlarged print is digitized for computer processing by tracing the outlines of the pebbles. From the size and shape of the projection area of the individual pebble images the computer determines the ellipsoids of revolution, classifies these ellipsoids, and establishes their grain-size distribution in percentage by weight. Thus photo-sieving differs distinctly from point-counting techniques. With the aid of photo-sieving, the surface grain-size distributions of larger sedimentary systems may be regularly mapped. Alluvial fans, braided rivers, both onshore and offshore coasts or areas of relict sediments and manganese nodules are suitable for this method.

Layer-resolved shifts of photoemission and Auger spectra from physisorbed rare-gas multilayers.

Abstract: Rare-gas multilayers adsorbed on Pd(111), Pd(001), and Al(111) were studied with photoemission and Auger spectroscopy. The Xe 4d core levels and the Xe N/sub 4,5/O/sub 2,3/O/sub 2,3/ Auger transitions show layer-resolved shifts for Xe multilayers on these three substrates. A simple model explains the experimental results satisfactorily. The core-level binding-energy shifts relative to the gas phase are dominated by the final-state hole-screening effect. The Auger kinetic-energy shifts relative to the gas phase, dominated by the difference in initial- and final-state hole-screening energies, are about minus three times the corresponding core-level shifts. The screening energies were calculated using a jellium model for the substrate and a dielectric continuum model for the rare-gas adlayer. Surface-induced shifts of core-level binding energies and Auger kinetic energies for bulk solid Xe(111) were also observed; the theoretical shifts are in very good agreement with the experimental values. The valence levels for multilayers of Ar, Kr, and Xe on Pd(001) were studied. They showed qualitatively similar shifts as the core levels, but the results cannot be explained accurately by our model, because the valence excitations are not as localized as the core excitations. Using spacer layers of Kr and Xe with various thicknesses, the effect of metallicmore » substrate screening on the valence-level shifts of Ar was demonstrated. The issues related to a proper energy-reference level and the question of ionic versus neutral excited states will be discussed.« less

Bilateral testicular germ cell tumors. Report of nine cases and review of the literature.

Abstract: In a series of 181 patients with testicular germ cell tumors, the phenomenon of bilateral involvement of the testicles was observed nine times (5%) Two patients evidenced a simultaneous bilateral tumor, and, in seven others, a second tumor occurred after an interval ranging between 8 months and 6 years and 11 months The incidence, histologic findings, therapy, and prognosis of bilateral testicular tumors are discussed on the basis of a survey of the literature Emphasis is placed on the significance of a long-term follow-up period as well as on the important role of sonography in the early detection of a contralateral tumor

Metal optics near the plasma frequency

Abstract: Near the plasma frequency spatial dispersion is an important effect in metal optics, since it leads to optical excitation of plasma waves. We outline an extension of local metal optics, which takes this effect into account via the hydrodynamical approximation for the electron motion and appropriate additional boundary conditions. We discuss a number of successful applications including an analysis of the fields near the surface. Finally, we review other methods dealing with nonlocal optics near a metal surface and comment on the theoretical limitations and practical merits of the hydrodynamical approach.

Magnetic resonance imaging (MRI) in different stages of myocardial infarction using the contrast agent gadolinium‐DTPA

Abstract: We investigated 26 patients admitted to our catheterization laboratory with a diagnosis of acute myocardial infarction. In each case acute revascularization was unsuccessful, but the diagnosis was confirmed by angiography. In 11 patients with an uncomplicated course of acute myocardial infarction magnetic resonance imaging was carried out within 7 days of the acute event. In three additional cases imaging was performed within 3 weeks, while a remaining 12 patients underwent studies more than 3 weeks after the onset of symptoms. We determined signal intensity at three points within the area of infarction and at three other points in adjacent myocardial tissue. Decreased signal intensity within the area of infarction was present in native scans in 60% of all cases. Application of 0.1 mmol/kg body weight gadolinium-DTPA was followed by an average 70% increase in signal intensity within zones of acute infarction, as compared to a 20% increase in surrounding myocardial tissue. In cases of subacute and chronic infarction there was no significant signal enhancement after administration of gadolinium-DTPA. Uptake of gadolinium-DTPA in the area of acute myocardial infarction may be a positive marker of acute myocardial necrosis, which may be of potential clinical benefit.