Showing papers by "Heidelberg University published in 1976"

Electrons in disordered systems. Scaling near the mobility edge

Abstract: Renormalization group arguments are applied to an ensemble of disordered electronic systems (without electron-electron interaction). The renormalization group procedure consists of a sequence of transformations of the length and the energy scales, and of orthogonal transformations of the electronic states. Homogeneity and power laws are obtained for various one and two-particle correlations and for the low-temperature conductivity in the vicinity of the mobility edge. Two types of fixed point ensembles are proposed, a homogeneous ensemble which is roughly approximated by a cell model, and an inhomogeneous ensemble.

Formal genetics of Fanconi's anemia

Abstract: The formal genetics of Fanconi's anemia were investigated on the basis of 21 families from different European countries, and of 69 families from the literature. Conclusions:

Stratified waters as a key to the past

Abstract: Density stratification in lakes and oceans generate anoxic conditions below the pycnocline, and sediment facies mirror this development. A comparison of modern sediments deposited in stratified and non-stratified waters with sediments formed since the Cambrian reveals that the ancient sea has been stratified a number of times.

The iso-renin angiotensin systems in extrarenal tissue

Abstract: Angiotensin is produced by the action of a specific enzyme on a protein substrate called angiotensinogen. The enzyme which is synthetized in the kidney and released into the blood is called renin (E.C. 3.4.4.15). Research on the renin-angiotensin system (RAS) has been centred almost exclusively around the kidney. The triple action of angiotensin, the effector peptide of the system, on (1) vasoconstriction, (2) aldosterone secretion and (3) sodium reabsorption, is the basis for the classical role of the kidney RAS in blood pressure regulation. Angiotensin can also be generated by enzymes of extrarenal origin. These enzymes will be called tissue iso-renins in this review and we shall focus the main interest on the iso-renin angiotensin systems (iso-RAS) in extrarenal tissue. The term renin will be used in this article with reference to enzyme arising from the kidney, to the plasma enzyme and to the clinically important classical RAS. The term iso-renin will be used when referring to a renin-like enzyme having its source in extrarenal organs. Similarly the term iso-RAS will refer to extrarenal tissues as opposed to the classical RAS in the kidney and plasma (Fig. 1). We believe that the term iso-renin can be justified, because the extrarenal enzymes form angiotensin as does kidney renin, but iso-renins differ biochemically from kidney renin and they are synthesized independently of the kidney. In the future it may be advantageous, however, to adopt a more systematic nomenclature in analogy to the kininogenase system and call the kidney enzyme angiotensinogenase instead of renin ; the angiotensin forming enzymes in extrarenal tissues would then have to be designated brain angiotensinogenase, adrenal angiotensinogenase etc. It is not intended to give a complete review of the existing literature in this field, which may be obtained from recent publications (Page & McCubbin, 1968; Gross, 1971 ; Ganten, 1972; Ganten et al. 1973; Skeggs et al., 1974). We rather wish to present new aspects of the tissue iso-renin angiotensin system as a local cellular enzymatic system. A local role of angiotensin within the kidney has been postulated (Thurau, 1974). The secretion of renin into the blood and its clinical role has been investigated more extensively,

Canonical and grand canonical Gibbs states for continuum systems

Abstract: It is shown that for a large class of interactions any canonical Gibbs state satisfying a natural temperedness condition is a mixture of Gibbs states with appropriate activities, and vice versa. Some general results on Gibbs states and canonical Gibbs states are established. In particular, a differential characterization of Gibbs states is given.

Spins, moments and charge radii in the isotopic series 181 Hg- 191 Hg

Abstract: The hyperfine structure splitting and the isotope shift in the (6 s2 1S0 - 6s 6p3P1,λ=2,537 A) line of very neutron deficient Hg isotopes were determined by the β radiation detected optical pumping method (β-RADOP). In addition, nuclear magnetic resonance was observed in the atomic ground state. The results are Mean-square nuclear charge radii are calculated. Interpreting the sudden change of nuclear radius between187Hg and185Hg δ〈r2〉187,185=0.42(5)fm2 as oblate-prolate shape transition, one obtains δ〈β2〉 =0.054(5).

Microscopic transport theory of heavy-ion collisions

Abstract: Drift and diffusion coefficients for the variables of mass fragmentation and excitation energy are studied for deeply inelastic collisions. The transport coefficients are obtained in closed form as functions of the parameters of the interaction matrix elements between nucleonic states and as functions of the binding energy of the intermediate rotating quasimolecular configuration. Drift and diffusion coefficients for excitation and mass transfer are related (dissipation fluctuation theorem). In good approximation these relations take the simple form of Einstein's relation between the mobility and the diffusion coefficient of a particle in a medium. For the total mass numbers 100, 250 and 500 the results are discussed in detail. The transport coefficients are compared with experimental results. Within the uncertainties of determination from experimental data, the drift and diffusion coefficients are well described by two previously adjusted parameters of the mean interaction matrix elements. Consequences for the production of superheavy elements in deeply inelastic collisions of U on U or Cf are discussed.

Bile salt glucuronides: identification and quantitative analysis in the urine of patients with cholestasis.

Abstract: . Glucuronides of lithocholate, chenodeoxycholate and cholate were synthesized enzymatically and characterized by thin layer chromatography, column chromatography and specific enzymatic hydrolysis. Bile salt glucuronides were quantitatively analysed in the urine of patients with intra- and extra-hepatic cholestasis and were found to be present in 19 out of 20 patients studied. Our patients with intrahepatic cholestasis excreted 8.9 mg non-sulphated and non-glucuronidated bile salts, 18.2 mg sulphated bile salts and 7.2 mg glucuronidated bile salts. The patients with extrahepatic cholestasis excreted 14.7 mg non-sulphated and non-glucuronidated bile salts, 20.7 mg sulphated bile salts and 4.7 mg glucuronidated bile salts. These findings indicate that glucuronidation of bile salts occurs in man and represents a metabolic pathway in patients with cholestasis.

CO2 reduction to formate by NADH catalysed by formate dehydrogenase from Pseudomonas oxalaticus.

Abstract: The direct reduction of CO2 to formate is catalysed by formate: NAD oxidoreductase in the presence of substrate amounts of NADH. Proof for this reaction is supplied by the detection of a CO2-dependent NADH oxidation, and by the identification of [14c] formate as the product of a NADH-dependent reduction of [14c]carbonate. The enzyme-catalysed CO2 reduction by NADH attains the equilibrium predicted by thermodynamic considerations, a state which is also reached from the formate side. The Michaelis constant for CO2 is about 40 mM indicating the low affinity of the enzyme for this substrate. The corresponding value for formate is 0.1 mM. Under the special conditions employed the enzyme catalyses the formate oxidation about 30 times faster than the CO2 reduction. That CO2 and not HCO3- is the active species in the reduction was shown by comparing the ph dependency of the velocities of the forward and back reactions and by observing the kinetics of CO2 reduction during the simultaneous attainment of the CO2-HCO3- equilibrium.

Studies on the digestive enzymes of the stomachless bonefish Carassius auratus gibelio (bloch): Endopeptidases

Abstract: 1. 1. In the digestive system of Carassius auratus gibelio trypsin- and chymotrypsin-like proteases were found, but no pepsin, no elastase and no collagenase. 2. 2. The occurrence of these enzymes as zymogenes in the hepatopancreas was shown. 3. 3. The endopeptidases are seryl-proteases. 4. 4. Unlike bovine trypsin and chymotrypsin, the Carassius endopeptidases are unstable below pH 6. The proteinases are not stabilized or activated by Ca-ions.

Activation and inhibition of muscle and cutaneous postganglionic neurones to hindlimb during hypothalamically induced vasoconstriction and atropine-sensitive vasodilation

Abstract: 1. Discharge patterns in postganglionic neurones to muscle and to hairy skin of the hindlimb of chloralose anaesthetized cats were investigated during electrical hypothalamic stimulation which induced either vasoconstriction or atropine sensitive vasodilation in the skeletal muscle. 2. Spontaneously active postganglionic neurones to muscle were activated both during hypothalamically induced vasoconstriction and active vasodilation. Stimulation of the hypothalamic vasodilator area induced mostly a sequence of activation-depression-activation in these neurones. Stimulation of cutaneous Group IV afferents elicited reflexes in these neurones; repetitive high frequency stimulation of large diameter afferents in the vago-depressor nerve produced depression of spontaneous activity followed by a postinhibitory excitation. The characteristics of these neurones fit those that would be expected of vasoconstrictors. 3. Normally inactive postganglionic neurones to skeletal muscle could only be activated during hypothalamically induced atropine sensitive vasodilation. These neurones exhibit no reflexes on somatic stimulation. The axons of these neurones conduct faster than those of the spontaneously active postganglionic neurones. It is likely that they are cholinergic vasodilator neurones. 4. Most of the cutaneous postganglionic neurones to hairy skin were activated during stimulation of both the hypothalamic vasoconstrictor and the vasodilator areas. These neurones have the characteristics of cutaneous vasoconstrictor neurones. Part of the cutaneous not spontaneously active postganglionic neurones could neither be activated from the hypothalamus nor by somatic stimuli.

Chemical Ecology—A Chapter of Modern Natural Products Chemistry†

Abstract: The chemical reaction of arthropods to their environment, i.e. their chemical ecology, can be studied particularly well with water beetles. Stenus comma, an aquatic beetle weighing only 2.5 mg, saves itself from drowning with the aid of an alkaloid, and the water beetle Ilybius fenestratus defends itself against small mammalian predators with a compound belonging to the same class. The water beetle Platambus maculatus employs a diterpene for precisely the same purpose and the whirligig beetle a norsesquiterpene, which also offers protection against troublesome microorganisms. As chemical artists, the ants can hardly be surpassed. In particular, the myrmecine ants guarantee their food supplies with plant growth substances. Since these compounds, depending upon concentration, can also act as inhibitors, we are confronted with an excellent example of an ecological equilibrium being established with the aid of organic chemicals. Even the little parasitic bombardier beetle Paussus favieri is tolerated, on account of its defensive chemistry, in the nest of the myrmecine ant Pheidole. In contrast, inorganic compounds are largely responsible for the stability of spiders' webs.

Intracellular distinction between peroxidase and catalase in exocrine cells of rat lacrimal gland: a biochemical and cytochemical study.

Abstract: The lacrimal gland (Glandula orbitalis externa) of rat contains both peroxidase and catalase and was used as a model for biochemical and cytochemical distinction between peroxidase and catalase. Both enzymes were isolated by ammonium sulfate precipitation from tissue homogenates, and the effects of fixation with glutaraldehyde and various conditions of incubation were investigated colorimetrically using DAB as hydrogen donor. The lacrimal gland peroxidase is strongly inhibited by glutaraldehyde treatment. In contrast, for catalase the fixation with glutaraldehyde is the prerequisite for demonstration of its peroxidatic activity. The maximal peroxidatic activity was obtained after treatment of catalase with 3% glutaraldehyde, higher concentrations being inhibitory. For lacrimal gland peroxidase, the maximal rate of oxidation of DAB is at pH 6.5, whereas for catalase it is at pH 10.5. The optimal concentration of H2O2 for lacrimal gland peroxidase is at 10−3 M and for peroxidatic activity of catalase at 10−1 M. These optimal conditions obtained biochemically were applied to tissue sections of rat lacrimal gland. After the fixation of tissue with a low concentration of glutaraldehyde and incubation in the DAB medium at neutral pH containing 10−3 M H2O2 (Peroxidase medium), the reaction product was localized in the cisternae of the rough endoplasmic reticulum, in elements of the Golgi apparatus, and in secretory granules. After the fixation of tissue with 3% glutaraldehyde and incubation in the DAB-medium containing 10−1 M H2O2 and at pH 10.5 (catalase medium), the staining in the endoplasmic reticulum, the Golgi-apparatus and in secretory granules was completely inhibited and reaction product was localized exclusively in small (0.2–0.5 μ) particles similar to small peroxisomes described in various other cell-types.

Distribution of RNA polymerase on Drosophila polytene chromosomes as studied by indirect immunofluorescence.

Abstract: Using indirect immunofluorescence visualization techniques we investigated the in situ distribution of RNA polymerase B on Drosophila melanogaster polytene chromosomes. The enzyme was found at many sites distributed throughout the genome in a pattern clearly distinct from that observed for histone H1, but it was especially concentrated in puffs induced by heat shock.

Lake sediments as indicators of heavy-metal pollution

Abstract: Heavy metals are one of the most toxic forms of environmental pollutants, constituting a threat both to aquatic life and the quality of drinking water. By analyzing lake sediments, it is possible to determine the provenance, distribution, extent, and also the possible hazards of metal contamination. Sedimentary cores, in particular, provide the means for evaluating the different influences from natural and civilizational sources; they represent a historical record of the metal accumulations which have taken place during the past decades as a result of population growth and industrial development.

Changes in vascular smooth muscle sensitivity to vasoconstrictor agents induced by corticosteroids, adrenalectomy and differing salt intake in rats.

Abstract: 1. Isolated hind limbs of rats were perfused and vascular smooth muscle sensitivity to noradrenaline, methoxamine and potassium chloride was measured and dose-response curves were obtained. 2. The sensitivity of vascular smooth muscle to noradrenaline is attenuated by adrenalectomy and low sodium diet; it is enhanced by corticosterone. High sodium diet or administration of deoxycorticosterone did not alter the dose—response curve significantly. 3. The increased sensitivity of vascular smooth muscle after corticosterone treatment is not related to changes in the contractile protein or alterations in the neuronal uptake and extraneuronal metabolism of noradrenaline. 4. These results suggest that the increased sensitivity in corticosterone-treated rats may be due to the number of receptors, receptor affinity to noradrenaline, or changes in the functional link between receptor and contractile apparatus.

Induction of point mutations by different chemical mechanisms in the liver microsomal assay

Abstract: A selection of chemical agents with different mechanisms of chemical mutability was tested with the liver microsomal assay by using different bacterial tester strains, namely: Salmonella typhimurium TA 1535, TA 1536, TA 1537, TA 1538 and G46. The tested agents had been selected according to the following criteria. They are all well-known mutagens and can be divided into alkylating agents, anti-metabolites, acridines and those that form radicals in the cell. The mutagens were: dimethylnitrosamine (DMN), diethylnitrosamine (DEN), methyl-nitro-nitrosoguanidine (MNNG), cyclophosphamide, Captan, amethopterine, azathioprine, 6-mecaptopurine, trypaflavine, isoniazide and hydrazine. All except amethopterine gave positive results, showing that this system is very sensitive. In a comparison of the different strains and mutagens we found a correlation between the diameter of the molecule and the permeability of the bacterial cell membrane.

Ultrastructure of sieve-element plastids inCaryophyllales (Centrospermae), evidence for the delimitation and classification of the order

Abstract: The orderCaryophyllales (Centrospermae) was found to contain specific P-type sieve-element plastids which are characterized by protein inclusions composed of ring-shaped bundles of filaments and of central crystalloids. The sieve-element plastids of 14 families (140 species investigated) fit into this overall characterization, and more specific details are used to delimit the families and arrange them within the order.Phytolaccaceae, the basic family of the order display much diversity: the crystalloids inside their plastids are either globular (most genera) or polygonal (Stegnosperma), starch may also be present (Phytolacca).Nyctaginaceae, with starch inBougainvillea sieve-element plastids, can be derived directly fromPhytolacca. Globular crystalloids are present in most of the families, as inDidiereaceae, Cactaceae, Aizoaceae-Tetragoniaceae, Portulacaceae-Basellaceae-Halophytaceae-Hectorellaceae. Caryophyllaceae andLimeum ofMolluginaceae contain polygonal crystalloids (otherMolluginaceae with globular crystalloids). Crystalloids are entirely absent fromChenopodiaceae (incl.Dysphaniaceae) andAmaranthaceae. The probable relationships between these families are presented diagrammatically in Fig. 13. Bataceae, Gyrostemonaceae, Vivianiaceae, Theligonaceae, Polygonaceae, Plumbaginaceae, Fouquieriaceae, Frankeniaceae, andRhabdodendraceae—all at some time included into theCaryophyllales (Centrospermae) or doubtfully referred to them—develop S-type (or different P-type) sieve-element plastids. Their direct connection to theCaryophyllales therefore is excluded. Finally, evolutionary trends of theCaryophyllales are discussed.

Comparison between child cadavers and child dummy by using child restraint systems in simulated collisions

Abstract: At present, numerous restraint systems for children applied in vehicles are in general considered for the use on the back seats. Up to now, only impact tests with dummies and animals have been carried through by these systems. Out of the great number of children, seats and belts we used a system (deformable safety impact table combined with a lap-belt) which has been investigated by us during frontal impacts utilizing two dummies and four cadavers of children in the age of 2 5 up to 11 years having body weights of 16 up to 31 kg. The tests have been conducted on the deceleration-sled track at the Institute of Legal Medicine of the University Heidelberg. Impact velocities of 30 km/h and 40 km/h at a medium deceleration of 20g have been chosen. None of the test sugjects showed injuries to the inner organs; however, numerous muscular hemorrhages as well as hemorrhages of discs and ligaments were noticed. The HIC values lay between 100 and 500; accelerations in x-direction up to 44g and in z- direction up to 85g occurred at the head. Lap-belt forces of 160 up to 400 daN were measured. A weak point of the investigated system is that the child's movements are considerably limited, a factor also noticed in other child restraint systems; however, the protective function proved to be an advantage. The movements during the impact, pictured by high-speed cameras, essentially differ from those of adults wearing 3-point belts. The maximum flexion of the vertebral column is, due to the system, located in the transition of the thoracic to the lumbar vertebral column and the flexion angles amounted about 90 degrees. As expected were the maximum head displacements in relation to a sled-fixed axis dependent on the impact velocity and the body height, and ranged between 50 cm (crash velocity 30 km/h, body height 97 cm) and 90 cm (crash velocity 40 km/h, body height 139 cm). The movement will be analyzed; the anatomical and mechanical causes are going to be investigated. Finally, the results will be compared with similar dummy tests investigated by use. Due to these differences in the dummy and cadaver behavior, the necessity is pointed out to examine all restraint systems by cadaver tests. /Author/

Ultrastructure of perfusion-fixed fetal capillaries in the human placenta

Abstract: The ultrastructure of human placental capillaries was investigated using perfusion fixation and the freeze-fracturing technique. The capillaries have a continuous endothelium especially rich in microfilaments, whereas micropinocytotic vesicles are exceedingly scarce. The endothelial cells are connected by three types of junctions: (1) zonulae occludentes characterized by 2 to 4 focal regions of membrane contact in thin-sectioned specimens and an equal number of ridges on the membrane E-face in freeze-fractured specimens; (2) small gap junctions associated with the zonula occludens. (3) attachment plaques resembling zonulae adhaerentes in their fine structure. Endothelial cells are provided with long, circularly oriented pseudopodial extensions, which may be responsible for intermittent constrictions of the vessel lumen. These findings indicate that diaplacental transport at the level of the fetal capillary is controlled by the cytoplasm of the endothelial cells and probably occurs only to a very limited extent by way of micropinocytotic vesicles.