Showing papers by "Free University of Berlin published in 1974"
TL;DR: In this paper, the ordering of the hydrocarbon chain interior of bilayer membranes has been calculated using the molecular field approximation developed in previous work on liquid crystals, and different statistical averages are evaluated by exact summation over all conformations of a single chain in the field due to neighboring molecules.
433 citations
183 citations
TL;DR: Lipid nonequilibrium is tentatively suggest as one possible cause for certain shape transformations of red blood cells.
Abstract: The role of lipid exchange in the curvature elasticity of bilayers is studied theoretically. Blocking of exchange between the monolayers may give rise to a nonequilibrium lipid distribution going hand in hand with a spontaneous curvature. Some possible consequences for vesicular deformations are discussed. Lipid nonequilibrium is tentatively suggest as one possible cause for certain shape transformations of red blood cells
160 citations
TL;DR: In this paper, a model that describes the dynamics of heavy ion collisions leading into the compound system is presented, which is able to reproduce most of the data on the compound formation cross-section.
136 citations
TL;DR: In this paper, an explanation for the formation of small vesicles by sonication of lecithin suspensions is given, and a formula for the vesicle size involves the edge energy of the bilayer and its curvature elastic energy.
122 citations
TL;DR: Water vapour from subsaturated atmospheres has been demonstrated in a variety of terrestrial insects and mites but no previous effort to identify the site and mechanism has been completely conclusive.
Abstract: UPTAKE of water vapour from subsaturated atmospheres has been demonstrated in a variety of terrestrial insects and mites but no previous effort to identify the site and mechanism has been completely conclusive. The tracheal system, the rectum and the general body surface have variously been proposed in specific studies.
120 citations
TL;DR: The influence of treatment with progesterone and with 4 synthetic progestagens for 6 days on sodium balance and on different factors of the renin-aldosterone system was investigated in 20 young healthy men on a fixed sodium intake.
Abstract: The influence of treatment with progesterone and with 4 synthetic progestagens (megestrol-acetate, dydrogesterone, norethisterone-acetate, d-norgestrel) for 6 days on sodium balance and on different factors of the renin-aldosterone system was investigated in 20 young healthy men on a fixed sodium intake (83 mEq/day). 50 mg of progesterone im caused, as expected, natriuresis, an increase in plasma renin activity (PRA), plasma angiotensin II concentration (PAC) and aldosterone excretion (AER), while plasma renin substrate concentration (PRS) remained unchanged. Progesterone levels during treatment were somewhat lower than in the luteal phase of normal menstrual cycles in women. Megestrol-acetate (15 mg/day) did not influence sodium balance, but led to a slight increase in PRA and AER after 3 days of treatment. PAC and PRS remained unchanged. Dydrogesterone (30 mg/day) caused slight sodium retention after 3 days of treatment and a concomitant increase in PRA, PAC (upright posture) and AER, but PRS w...
109 citations
TL;DR: The behavior of heterochromatin during premature chromosome condensation (PCC) was studied in a cell line of Microtus agrestis after fusion with mitotic HeLa cells.
Abstract: The behaviour of heterochromatin during premature chromosome condensation (PCC) was studied in a cell line of Microtus agrestis after fusion with mitotic HeLa cells. In the G1- and G2-PCC, the heterochromatic nature of the X-chromosomes was detectable by their intense staining. The pulverized appearance of the S-phase PCC was correlated with incorporation of 3H TdR into the DNA. Three types of S-PCC were observed. PCC with a pulverized appearance of: (a) only the autosomes (early S); (b) autosomes and X-chromosomes (mid S); and (c) only the X-chromosomes (late S). The behaviour of heterochromatin during replication, as observed by the PCC method, was no different from that of euchromatin. The data on the sequence of chromosome replication indicate that the centromeric regions of the X-chromosomes were the last segments to replicate. The completion of DNA synthesis in the X-chromosomes appears to be followed by progressive chromosome condensation during G2 even before the actual initiation of prophase.
107 citations
TL;DR: Cannabinol and Cannabidiol were tested in several test procedures known to be altered by δ9-tetrahydrocannabinol (THC) or crude cannabis preparations and enhancement by CBD is best explained by an inhibition of THC-metabolism.
Abstract: Cannabinol (CBN) and Cannabidiol (CBD) were tested in several test procedures known to be altered by δ
9-tetrahydrocannabinol (THC) or crude cannabis preparations. They were inactive in doses up to 80 mg/kg in tests on animal motility, food and water intake, body temperature and catalepsy. In contrast, CBD enhanced the hexobarbitone “sleeping time” more pronounced than δ
9-THC whereas CBN increased the “sleeping time” only slightly. When administered in combination CBD prolonged all actions of THC, whereas CBN selectively blocked the effect of THC on hexobarbitone “sleeping time”. The enhancement by CBD is best explained by an inhibition of THC-metabolism.
73 citations
TL;DR: Information theory is applied to data from microelectrode recordings of the cat's afferent visual system in a manner more general than hitherto usual and it is shown that it is not necessary to know the particular neuronal code for information calculations by taking the signal itself as the symbols.
Abstract: Information theory is applied to data from microelectrode recordings of the cat's afferent visual system in a manner more general than hitherto usual. It is shown that it is not necessary to know the particular neuronal code for information calculations by taking the signal itself as the symbols. Uncontrollable errors thus can be avoided. It is further shown that by this approach the dynamical behaviour of the system is fully considered for information transfer. Quantities are defined to exhibit the time course of transmitted information.
68 citations
TL;DR: The results demonstrate the limited degradation of dgt in man and suggest that the pharmacologic effects are mediated by dgt itself.
Abstract: The levels of digitoxin and its metabolites in the plasma, urine, and feces of 6 subjects given a single oral dose of 1 mg 3H‐dgt have been determined using CHCl3‐extraction and thin‐layer chromatography (TLC). The peak plasma level of 4.1% of the given dose per 1 plasma occurred at 40 min after drug administration and was followed by an exponential decline with a mean half‐life (T/2) of 6.8 days. The T/2 of the eliminated radioactivity in urine and feces was 7.2 and 4.8 days, respectively. Within 192 hr, 22% of the given dose has been excreted in urine and 13% in feces. The TLC separation of the CHCl2‐soluble fraction in plasma yielded the unchanged digitoxin (dgt) and traces of digitoxigenin‐bisdigitoxoside (dgt‐bis). In urine, dgt accounted for 60% of the eliminated amount within the experimental time. Dgt‐bis and the hydroxylated products digoxin (dg) and dgt‐bis were also found in lesser anwunts. The monodigitoxoside of digitoxigenin (dgt‐mono) could be denwnstrated as a conjugative partner of glucuronic acid. In feces, the unchanged dgt and its monoderivative were the main excretion products. However, since dgt‐mono and the more polar compounds have shown an inverse relationship during the study, a bacterial cleavage following a conjugation of dgt‐mono and an enterohepatic circulation of its lipophilic nwiety are suggested. These results demonstrate the limited degradation of dgt in man and suggest that the pharmacologic effects are mediated by dgt itself.
TL;DR: In this article, a survey of research in atomic spectroscopy with accelerated, excited ions (beam-foil Spectroscopy) is given, with a short experimental section on atomic energy levels, radiative transition probabilities, a auto-ionization mechanism, fine-and hyperfine-structure effects and radiative corrections.
TL;DR: Evidence could be given that hypothyroidism is a graded phenomenon that is compensated during a certain period by supplementary production of triiodothyronine after radiation therapy.
Abstract: . During a follow-up examination of patients after radioiodine therapy for thyrotoxicosis, 128 patients without recurrent hyperthyroidism were investigated for the clarification of different degrees of hypothyroidism. The clinical diagnosis and the conventional tests for circulating thyroid hormones were compared to the estimation of serum thyroid stimulating hormone (TSH), and to the thyrotropin-releasing hormone (TRH) test, which was performed with 500 μg synthetic TRH I.V., and referred to age and sex specific normal ranges. Moreover, serum triiodothyronine (T3) was estimated by radioimmunoassay. Results: 1. A gradual classification of biochemical group-differences gave more significant discrimination than a division into groups based on clinical impression. Different grades of severity of hypothyroidism could be demonstrated by highly significant differences of free thyroxine index (FT4-Index) between the 1st group of patients with low FT4-Index and a 2nd group with raised basal TSH (and normal FT4-Index), between the 2nd group and a 3rd group with an elevated value of Δ TSHmax (and normal FT4-Index and basal TSH), and between the 3rd group and a 4th group of biochemically normal reacting patients and controls. There was a less significant difference with very considerable overlap between clinically established groups. 2. T3-uptake, total T4 and FT4-Index are not sufficient for detecting hypothyroidism in individual patients, although their group-differences are significant in biochemical classification. 3. Neither between clinical nor between biochemical groups was there any significant correlation with serum cholesterol. 4. Triiodothyronine can be normal or elevated in a situation with low T4 and raised TSH concentrations. Conclusions: Evidence could be given that hypothyroidism is a graded phenomenon. Its classification by biochemical data is more reasonable than a clinical division. Advancing severity of hypothyroidism after radiation therapy is compensated during a certain period by supplementary production of triiodothyronine. As thyroid hormone concentration in patients with pathological serum TSH or TRH-test is significantly lower than in euthyroid patients or in controls, replacement therapy in early stages of hypothyroidism also seems reasonable.
TL;DR: In this paper, aortic arch angiography is the most suitable radiological technique in the diagnosis of brain death, and the angiographic findings in patients with brain death are described.
Abstract: The angiographic findings in patients with brain death are described. The authors believe that aortic arch angiography is the most suitable radiological technique in the diagnosis of brain death.
TL;DR: It was found that in monkey cells both the viral transcription and viral translation were reduced by the same rate by human interferon, which supports the hypothesis that the SV40 genome transcription is primarily affected by interferons.
TL;DR: In this article, it is shown that in quantum field theory one is in general dealing with representations of the universal covering group of the conformal group of a quantized field, and that the apparent conflict with Einstein's causality principle is resolved.
Abstract: Finite conformal transformations for quantized fields are obtained. The apparent conflict with Einstein's causality principle is resolved. It is shown that in quantum field theory one is in general dealing with representations of the universal covering group of the conformal group.
TL;DR: In this article, the effect of piezc-electricity on deformation in a Schadt-Helfrich-cell is discussed, and the maximum angle of tilt γ m increases to almost π/2 even in a weak field.
Abstract: At rest between two metallized glass plates a nematic liquid shows a screw-like deformation pattern if one turns the plates by an angle ωm around an axis perpendicular to the plates. If a voltage U is applied, the molecules are tilted with respect to the electric field when U exceeds a threshold voltage. With increasing amount of twist ωm the maximum angle of tilt γ m increases to almost π/2 even in a weak field. Numerical results are given for the Schadt-Helfrich-cell, i.e. ωmλπ/2. The effect of piezc-electricity on deformation in a Schadt-Helfrich-cell is discussed.
TL;DR: This work tested whether various B cell mitogens act on the same or on different subpopulations of B cells, divided into different chemical classes and different types of mitogens presumably react with different membrane surface constituents.
Abstract: WITH respect to maturation stage, function, and cell surface constituents, lymphocytes bearing immunglobulin on their (B cells) comprise a heterogenous population. It has been suggested1 that binding of mitogens to membrane surface surface constituents triggers the events leading to stimulation of cell mitosis. The various B cell mitogens can be divided into different chemical classes and different types of mitogens presumably react with different membrane surface constituents. According to these assumptions we tested whether various B cell mitogens act on the same or on different subpopulations of B cells.
TL;DR: The rats developed tolerance to the overall toxicity and to the anorexigenic effect of maphetamine, and the concentration of H3-d-amphetamine in brains of chronically treated rats is significantly higher than in controls.
Abstract: Female Wistar rats were treated chronically with d-amphetamine sulphate in drinking water. The concentrations of amphetamine were 0.01%, 0.02%, 0.03%, 0.04% and 0.05% in the 1st, 2nd, 3rd, 4th, and 5th week of treatment. The consumed doses of amphetamine increased from 16 mg/kg on the first day up to 90 mg/kg on the 36th day of treatment. The effects of chronic treatment with amphetamine on food intake, body weight and locomotor activity of rats were determined. The rats developed tolerance to the overall toxicity and to the anorexigenic effect of maphetamine. No tolerance to the effects of the drug on body weight and locomotor activity was observed. The concentration of H3-d-amphetamine in brains of chronically treated rats is significantly higher than in controls. No difference in the pattern of distribution of radioactivity among the subcellular fractions of rat brain was observed between control and chronically treated groups. The relationship between developmen tof tolerance and the concentration of amphetamine in the brain is discussed.
TL;DR: The elektronenmikroskopische Untersuchung von hydratisiertem biologischen material in feuchten Kammern bringt unvermeidliche, schwere Objektschadigungen mit sich Deshalb wurden diese Objekte tiefgekuhlt untersucht Das eingefrorene Praparat wurde dazu ohne Unterbrechung der Tiefkuhlung und ohne Aufwacbsen e
TL;DR: An elastic theory for simple lipid bilayers which may be viewed as two-dimensional fluids is posed and bilayer spheres in an aqueous medium can be deformed into ellipsoidal bodies if they are submitted to a magnetic field or excess outside pressure.
Abstract: In two previous publications1; 2 we have pro posed an elastic theory for simple lipid bilayers which may be viewed as two-dimensional fluids. In particular, we have shown that bilayer spheres in an aqueous medium can be deformed into ellipsoidal bodies if they are submitted to a magnetic field or excess outside pressure. Here we consider a possible deformation by electric fields. It will be seen that the electric effect can be quite strong for large vesicles. As before, we restrict ourselves to small deforma tions, assuming the bilayer to be unstretchable and the sphere to become an ellipsoid of revolution. To calculate the ellipticity we minimize the total ener gy consisting of curvature-elastic and electric parts. The conductivity of the bilayer will in general be very much smaller than that of the aqueous environ ment, so it seems permissible to treat the membrane as a perfect insulator. The electric energy of deformation may be ob tained from the Maxwell stresses. Those inside the membrane will be balanced by equal but opposite elastic stresses. The membrane is likely to sustain the latter without undergoing an appreciable defor mation as they induce neither curvature nor shear flow in the bilayer. The only unbalanced force is due to the Maxwell stress exerted by the electric field just outside the vesicle, since in the enclosed water the field must be identical to zero. We assume here that the membrane is dielectrically isotropic, which implies that the forces caused by the Maxwell stresses are confined to the interfaces with water. If it is not, electrical torque densities may be ex pected within the bilayer. The torques may induce curvature, but this should be negligible as the polarizabilities of the bilayer should be very much smaller than that of water. The standard expression for the electric potential Ue around a sphere in a uniform applied field is
TL;DR: In this article, the intensity of beam-foil-excited hydrogen atoms has been measured in electric fields alternately parallel and antiparallel to the beam at three energies (110, 165, and 210 keV) and three field strengths.
Abstract: The intensity of beam-foil-excited $\mathrm{Ly}\ensuremath{-}\ensuremath{\alpha}$ radiation has been measured in electric fields alternately parallel and antiparallel to the beam. Measurements were made at three energies---110, 165, and 210 keV---and three field strengths. From these data the $S\ensuremath{-}P$ co-herence term ${\ensuremath{\sigma}}_{\mathrm{SP}}$ has been determined. The magnitude of ${\ensuremath{\sigma}}_{\mathrm{SP}}$ is found to be 0.07 at 110 keV, 0.19 at 160 keV, and 0.22 at 210 keV. These results establish that beam-foil-excited hydrogen atoms have a nonzero electric dipole moment.
TL;DR: In insulin-treated alloxan diabetic rats some parameters of the hypothalamo-hypophysial-adrenocortical (HHA) system are normal: half-life and circadian rhythm of plasma corticosterone, maximal and submaxirnal stimulation of the adrenal cortex by exogenous and endogenous ACTH, dex-amethasone suppression of stress stimuli of different strengths.
Abstract: In insulin-treated alloxan diabetic rats some parameters of the hypothalamo-hypophysial-adrenocortical (HHA) system are normal: half-life and circadian rhythm of plasma corticosterone, maximal and submaxirnal stimulation of the adrenal cortex by exogenous and endogenous ACTH, dex-amethasone suppression of stress stimuli of different strengths. If insulin treatment is withheld, 40 hr after the last insulin injection morning levels of plasma corticosterone are elevated, adrenocortical response to exogenous ACTH is increased, the onset of dexamethasone inhibition of weak stress signals is delayed, different stress stimuli overcome the dexamethasone blockade. These disturbances of the regulation of the HHA-system could be interpreted as counter regulation in insulin-deficient alloxan diabetic rats. (Endocrinology 95: 760, 1974)
TL;DR: Experiments in which perfusion rate through the loop of Henle was varied demonstrated the existence of a feedback signal which originates downstream of the late proximal convolution and which affects filtration into individual early proximal segments.
Abstract: A new pressure transducer microperfusion system has been used to measure quantitatively SN GFR, early proximal free flow pressure and stop flow pressure of varying flow rates through the loop of Henle in the range of 0 to 50 nl/min. Perfusing the loop with an isoosmolal artificial tubular fluid at physiological flow rates SN GFR was 19.9±1.1 and 27.7±1.0 nl/min in two different strains of antidiuretic rats. SN GFR increased when loop perfusion was interrupted. The question whether a feedback control mechanism of SN GFR is operative in the rat kidney was evaluated in further experiments in which early proximal tubular pressure was measured in functionally isolated proximal convolutions in vivo under conditions of constant flow as well as stopped flow. Experiments in which perfusion rate through the loop of Henle was varied demonstrated the existence of a feedback signal which originates downstream of the late proximal convolution and which affects filtration into individual early proximal segments. This feedback mechanism exhibited an asymmetrical behaviour: Elevation of loop perfusion above the control value resulted in an early proximal pressure drop, under simulated free flow conditions as well as under stop flow conditions. In contrast lowering of perfusion rate below the predetermined physiological value had no significant effect on early proximal pressures.
TL;DR: In this paper, the synthesis and redox properties of polymers with various quinone-hydroquinone systems are summarized and a theoretical treatment is given for the redox behavior of tetra-and hexa-valent redox systems.
Abstract: This review summarizes our work on the synthesis and redox properties of polymers with various quinone–hydroquinone systems. Information is given on our attempts to increase the chemical stability of the redox resins by suitable substitution and by other methods. The redox properties were thoroughly investigated (e.g. redox potentials, redox capacity, rate of the redox reaction). A theoretical treatment is given for the redox behaviour of tetra- and hexa-valent redox systems. Redox resins can be used as insoluble, regenerable oxidants or reductants. By means of these resins some organic substrates could be dehydrogenated and several metal ions could be reduced or deposited.
TL;DR: In this paper, the authors indicate certain limitations to the elastic moduli and flexoelectric coefficients of liquid crystals in terms of their elasticity and elasticity properties, and their properties are discussed.
Abstract: Phenomenological and molecular considerations indicate certain limitations to the elastic moduli and flexoelectric coefficients of liquid crystals.
TL;DR: In this paper, the relationship between actual and geostrophic wind in the subcloud layer is determined from ship-borne radiosonde and radar wind observations during the Atlantic Trade Wind Experiment 1969 (ATEX) and the divergence of vertical transport of momentum between the sea surface and 500m height is computed by the ageostrophic method.
Abstract: From ship-borne radiosonde and radar wind observations during the Atlantic Trade Wind Experiment 1969 (ATEX) the relation between actual and geostrophic wind in the subcloud layer is determined. The frictional force and the divergence of vertical transport of momentum between the sea surface and 500-m height are computed by the ageostrophic method.
Along the surface wind direction, balance between pressure gradient and frictional force is closely established. Perpendicular to the surface wind the expected balance of pressure gradient and Coriolis force is not obtained but a substantial frictional force results from this component.
The boundary condition that the stress vanishes at the lowest wind maximum leads to an underestimation of surface stress by about 35 per cent. It is suggested that convective transport of momentum must take place in the subcloud layer.
TL;DR: Padagogische Teildisziplin: Vergleichende Erziehungswissenschaft; Sonstige; ÃÂÃÂs elektronischer Volltext verfugbar as mentioned in this paper.
Abstract: Frankfurt am Main; Oslo : International Peace Research Association, Education Committee 1974, XI, 378 S.
Padagogische Teildisziplin: Vergleichende Erziehungswissenschaft; Sonstige;
als elektronischer Volltext verfugbar
TL;DR: Kinetic studies with glucose pretreated stationary cells reveal a strong competitive inhibition pattern between adenine, guanine, hypoxanthine, and cytosine, indicating that all the four bases are accepted by this special transport system.
TL;DR: The Mossbauer effect of Cu:Fe has been measured for $30 \mKlTl100 \mathrm{K}$ in external fields up to 60 kg.
Abstract: The M\"ossbauer effect of Cu:Fe has been measured for $30 \mathrm{mK}lTl100 \mathrm{K}$ in external fields up to 60 kg. A constant temperature-independent term is subtracted from the hyperfine fields. After this correction the local susceptibility is in agreement with bulk magnetization, neutron diffraction, and NMR data. At the very lowest temperatures the local susceptibility becomes temperature independent, in agreement with theoretical expectations.