Showing papers by "Ludwig Maximilian University of Munich published in 1978"

Catalytic Aluminas: Surface Models and Characterization of Surface Sites

Abstract: Aluminas have been used extensively as adsorbenu and active catalysrs and catalyst supponsm the pas. Already in 1197 the aluminadyzed dehydration of ettllnoi was dtscavered by Dutch chermsts: and S;rbatier [3] remewed the use of dumlnas as active cazaiysrs far vanous reacttons UI the second decade of thu century. She that time the applicazions of aluuuas m dycic pmcesses have mcreased tremendously. In tndustrral cualytic pmcesses, alumuus are mostiy used as catalyst suppons [4]. Oxides a d mued oxides ap well as tracuuion mauls and noble meare supported oa alumma. Thuscb. romaa-elumana catalysts are ktng used for the conversion of parafdns to olailnrc hydrocarbons, 10 hydrodealkplation of aromatics. and to a lesser exzm in catalyzic reforming. The larter process LS also caralyzed by molybdena-alumina, a cavlyst system whid is also active for malang toluene and ocher aromatics from satwed hydrocarc bons. It also dyzes the Isomerhation of pm. Great efions are presently be-made to nudy the surface c...

Do Mitochondria Produce Oxygen Radicals in vivo

Abstract: 1 Heart mitochondria from rats at 3 months and 23 months of age were investigated for their capacity to generate oxygen radicals and hydrogen peroxide. 2 Highest values for O2+-formation were obtained with submitochondrial particles freed from superoxide dismutase after the addition of succinate and antimycin A to start the reaction. Under these conditions superoxide-radical formation with mitochondria from old rats (2.54 nmol × min−1× mg−1) exceeded formation rates in the young controls (1.9 nmol × min−1× mg−1) by 25%. 3 A constant fraction of 20% of the radicals produced escaped quenching by intramitochondrial superoxide dismutase. This fraction was independent of the rate of radical formation; its magnitude was deduced from generation rates of hydrogen peroxide in the presence and absence of exogenous superoxide dismutase. 4 Free oxygen radicals could be obtained with intact rat-heart mitochondria as well following the addition of ATP, a system which is closer to physiological states. Formation rates of oxygen radicals observed under these conditions were similar to those seen in the particulate fractions which escaped quenching by mitochondrial superoxide dismutase. 5 Peroxidative degradation of membrane lipids was found to parallel steady-state concentrations of free oxygen radicals. 6 The results are discusssed in terms of a radical-generating mechanism which functions in vivo at the level of the mitochondrial electron-transferring system.

Projections from the parvocellular vasopressin- and neurophysin-containing neurons of the suprachiasmatic nucleus.

Abstract: The efferent projections of the parvocellular vasopressin- and neurophysin-containing neurons of the suprachiasmatic nucleus (SCN) have been investigated in the mouse, rat and guinea pig, using specific antisera to vasopressin and neurophysin in the unlabelled antibody-enzyme immunoperoxidase method. In all three species, parvocellular perikarya containing vasopressin and neurophysin were found in the SCN, primarily in the medial, dorsal and rostral part of the nucleus. The fine-caliber vasopressin- and neurophysin-containing fibers arising from SCN neurons can easily be distinguished from the large-caliber vasopressin and neurophysin fibers of magnocellular neurons which pass from the supraoptic and paraventricular nuclei primarily to the neural lobe of the pituitary, but also to extrahypothalamic sites. Fine-caliber fibers leave the SCN in various directions to form several pathways. The major projections run (1) rostrodorsally to the lateral septum, and (2) dorsally to the medial dorsal thalamus and lateral habenula. Smaller projections course rostrally to the nucleus of the diagonal tract (of Broca), and dorsocaudally to the posterior hypothalamus and interpeduncular nucleus. In addition, many fibers of the dorsal thalamic projection continue beyond the lateral habenulae through the central grey of the mesencephalon to the area of the nucleus of the solitary tract. In all target areas, fibers were observed only in distinct portions of the nuclei and were not distributed to the whole nucleus. None of the fine-caliber fibers from SCN neurons project to, or even towards, the median eminence and neural lobe. No oxytocin-positive SCN neurons or fine-caliber fibers could be found. In Brattleboro rats, with hereditary vasopressin deficiency, no vasopressin- or neurophysin-positive SCN neurons or fine-caliber fibers could be found. In contrast to vasopressin and neurophysin fibers from magnocellular neurons of the supraoptic and paraventricular nuclei, fine-caliber vasopressin and neurophysin fibers from SCN neurons do not terminate at capillaries. A large number of these fibers make axo-somatic contacts with neurons in the projection areas. It is concluded that vasopressin and neurophysin from parvocellular SCN neurons are not released into the bloodstream, but may affect neurons in the projection areas described.

Raman scattering, superconductivity, and phonon density of states of stoichiometric and nonstoichiometric TiN

Abstract: Raman scattering and superconductivity of titanium nitride with various N deficiencies have been investigated. While in stoichiometric superconducting TiN second-order Raman scattering is predominant, first-order Raman scattering increases with increasing N deficiency. The first-order Raman spectrum which agrees well with the phonon density of states shifts to higher frequencies when the N deficiency grows. This frequency shift is particularly strong at small N deficiencies (\ensuremath{\sim}5%) and is coupled with a drastic drop of ${T}_{c}$. The shift of the phonon density of states indicates phonon anomalies in stoichiometric TiN at 200 ${\mathrm{cm}}^{\ensuremath{-}1}$ in close agreement with just performed neutron studies. In almost stoichiometric TiN the mean-square frequencies $〈{\ensuremath{\omega}}^{2}〉$ from the Raman spectra are in good agreement with corresponding specific-heat data. The similarities between the nonstoichiometric Ti${\mathrm{N}}_{0.55}$ and TiC are discussed.

Genetic differentiation during speciation.

Abstract: SPECIATION theory is still largely descriptive. How many and what kind of genes are implicated in speciation is a central unresolved problem of evolutionary biology1,2. Does speciation require major genomic changes3–5 or may minor ones suffice1,6–9? Similarly, does speciation depend on structural or on regulatory genes10? We have investigated these questions with reference to the actively speciating fossorial mole rats of the Spalax ehrenbergi complex in Israel, which comprises four morphologically indistinguishable chromosome forms (2n = 52, 54, 58, 60)11 adapted in that order to increasing aridity12. Narrow hybrid zones between karyotypes13 and mate selection14 (through olfaction15, vocalisation16 and aggression17) suggest that the recently18 formed species represent progressive stages of final speciation13. Genic diversity proved low, and genic similarity between karyotypes very high, in the previous test based on 17 gene loci of tissue proteins8. The test of eight additional loci of blood proteins, which is reported here, reinforces earlier conclusions and sheds light on the allozyme–environment association and on the amount of genetic differentiation during speciation.

Chemical composition of the peptidoglycan-free cell walls of methanogenic bacteria

Abstract: Cell walls were prepared from freeze-dried samples of 7 strains of Methanobacterium by mechanical disintegration of the cells followed by incubation with trypsin. Electron microscopy revealed the presence of sacculi exhibiting the shape of the original cells, on which no surface structure could be detected. Ultrathin sections of the isolated sacculi showed a homogenously electron dense layer of about 10–15 nm in width. The ash content varied between 8 and 18% of dry weight. The sacculi of all the strains contained Lys: Ala: Glu: GlcNAc or GalNAc in a molar ratio of about 1:1.2:2:1. In one strain (M. ruminantium M 1) alanine is replaced by threonine, however. Neutral sugars and-in some strains-additional amounts of the amino sugars were present in variable amounts, and could be removed by formamide extraction or HF treatment without destroying the sacculi. No muramic acid or d-amino acids typical of peptidoglycan were found. Therefore, the sacculi of the methanobacteria consist of a different polymer containing a set of three l-amino acids and one N-acetylated amino sugar. From cells of Methanospirillum hungatii no sacculi, but tube-like sheaths could be isolated, which tend to fracture perpendicularly to the long axis of the sheath along the fibrills seen on the surface. The sheaths consist of protein containing 18 amino acids and small amounts of neutral sugars. They are resistent to the proteinases tested and are not disintegrated by boiling in 2% sodium dodecylsulfate for 30 min. The three Gram-negative strains Black Sea isolate JR-1, Cariaco isolate JR-1 and Methanobacterium mobile do not contain a rigid sacculus, but merely a SDS-sensitive surface layer composed of regularly arranged protein subunits. This evidence indicates that, within the methanogens, different cell wall polymers characteristic of particular groups of organisms may have evolved during evolution, and supports the hypothesis that the evolution of the methanogens was separated from that of the peptidoglycan-containing procaryotic organisms at a very early stage.

Electron microprobe analysis of frog skin epithelium: evidence for a syncytial sodium transport compartment.

Abstract: For elucidation of the functional organization of frog skin epithelium with regard to transepithelial Na transport, electrolyte concentrations in individual epithelial cells were determined by electron microprobe analysis. The measurements were performed on 1-μm thick freeze-dried cryosections by an energy-dispersive X-ray detecting system. Quantification of the electrolyte concentrations was achieved by comparing the X-ray intensities obtained in the cells with those of an internal albumin standard. The granular, spiny, and germinal cells, which constitute the various layers of the epithelium, showed an identical behavior of their Na and K concentrations under all experimental conditions. In the control, both sides of the skin bathed in frog Ringer's solution, the mean cellular concentrations (in mmole/kg wet wt) were 9 for Na and 118 for K. Almost no change in the cellular Na occurred when the inside bathing solution was replaced by a Na-free isotonic Ringer's solution, whereas replacing the outside solution by distilled water resulted in a decrease of Na to almost zero in all layers. Inhibition of the transepithelial Na transport by ouabain (10−4 m) produced an increase in Na to 109 and a decrease in K to 16. The effect of ouabain on the cellular Na and K concentrations was completely cancelled when the Na influx from the outside was prevented, either by removing Na or adding amiloride (10−4 m). When, after the action of ouabain, Na was removed from the outside bathing solution, the Na and K concentration in all layers returned to control values. The latter effect could be abolished by amiloride. The other cell types of the epithelium showed under some experimental conditions a different behavior. In the cornified cells and the light cells, which occurred occasionally in the stratum granulosum, the electrolyte concentrations approximated those of the outer bathing meium under all experimental conditions. In the mitochondria-rich cells, the Na influx after ouabain could not be, prevented by adding amiloride. In the gland cells, only a small change in the Na and K concentrations could be detected after ouabain. The results of the present study are consistent with a two-barrier concept of transepithelial Na transport. The Na transport compartment comprises all living epithelial layers. Therefore, with the exception of some epithelial cell types, the frog skin epithelium can be regarded as a functional syncytium for Na.

Influence of mitochondrial radical formation on energy-linked respiration.

Abstract: 1 The earlier observation that aging promotes peroxidation of lipids within inner mitochondrial membranes by a radical-generating mechanism has provided a model for studying the relationship of membrane alterations to energy-linked respiration. 2 Electron transport was impaired as a function of age only in the presence of substrates oxidized within the inner mitochondrial membrane. Respiratory control ratios and P:O ratios decreased regardless of substrate identity. 3 Arrhenius kinetic data revealed age-dependent shifts of temperature breaks only for membrane-bound enzymes including oligomycin-sensitive ATPase. Specific activities decreased for all enzymes studied except cytochrome oxidase and the glutamate oxidase system. 4 Molecular motion data of spin-labelled fatty acid analogues associated with phospholipid bilayer from inner mitochondrial membranes exhibited a decrease in lipid fluidity in membranes from aged rats. 5 The exposure of isolated mitochondria to a O2−-radical generating system brought about identical changes in energy-linked respiration and oxidative phosphorylation as did aging in the animal. The effect was completely inhibited only in the presence of both superoxide dismutase and catalase, indicating the participation of O2−-radicals and H2O2 in causing the observed structural and functional changes. 6 The results support the concept of an active mechanism in mitochondria of living tissues which can contribute to pathophysiological processes by a sequential reaction involving radical-induced changes in the hydrophobic bonding of lipid-dependent enzyme systems.

Subcellular Metabolite Concentrations

Abstract: Mitochondrial and cytosolic contents of adenine nucleotides and phosphate were measured in perfused rat livers empolying a technique of fractionation of freeze-fixated tissue in non-aqueous solvents. From the subcellular contents the mitochondrial and cytosolic concentrations of ATP. ADP, AMP and phosphate and the phosphorylation potentials of the subcellular ATP systems were calculated. An attempt was made to elucidate the relationship between mitochnodrial and cytosolic adenine nucleoide systmes and the dependency on the metabolic state of the liver. The following results were obtaines. 1 Under all mtabolic conditions studied the mitochnodrial ATP/ADP ratios were considerably lower than the cytosolic ratios (mitochondria: 0.1–0.7); cytosol: 2–11). 2 The ATP/ADP ratios calculated from overall tissue contents refflect mainly the cytosolic rations. 3 An inverse relationship was found between mitochondrial and cytosilic ATP/ADP ratios, i.e. when the mitchondrial ratios tended to increase, the cytosolic ratios decrease and vice versa. 4 The phosphorylation potentials calculated from the subcellular concertratopms were higher in the cytosol that in the mitochondria. The potential difference varied between 11 and 3 kJ/mol in livers from fed and starved rats, respectively. 5 In the presence of mitochondrial inhibitors, i.e. amytal, dinitrophenol and carboxyatractyloside the potential difference between the subcellular ATP systems decreased predominantly due to an increase in the mitocnodrial ATP/ADP ratios. 6 A correlation between mitochondrial ATP/ADP ratios and the respiratory rates was not obsrved, but the subcellular ratios appeared to correlate with the rate of glycolysi. When the rate of lactate + pyruvate production was increased, the cytosolic ATP/ ADP ratios were increased, too, wheres the mitochondrial ratios tended to decrease. 7 The adenine nucleotides in the cytosol appear to be in near equilibrium catalysed by the adenylate kinase. In the mitochondria, the AMP concentration is much lowe than to be expected under equilibrium conditions. These results were discussed with respect to rate control of processes involved in ATP generation, i.e. Oxidative phosphorylation, adenine nucleotide translocation and glycolysis.

High‐Resolution, Higher‐Order UV/VIS Derivative Spectrophotometry

Abstract: Derivative spectrophotometry has gained increasing importance in the past two years and is currently experiencing vigorous development. Following and introduction the present article provides a review of this extremely effective method. In particular, the advantages of higher-order derivative spectrophotometry (HODS method, n > 2) are discussed on the basis of practical examples from a wide range of analytical fields. The results are achieved with the aid of a newly developed analog computer unit, whereby for the first time readily reproducible, low-noise, on-line spectra can be obtained up to the 7th order and even, in favorable cases, up to the 9th order. In practice it has proved valuable to work with spectra of the 3rd to 5th order; but even higher derivations could be profitable for the separation of strongly superposed signals or for “fingerprinting”.

Extrahypothalamic neurophysin-containing perikarya, fiber pathways and fiber clusters in the rat brain

Abstract: Immunoreactive neurophysin (Np) is demonstrated by the immunoperoxidase technique not only within neurones of the classical hypothaiamo-neurohypophyseal system, but also in extrahypothalamic perikarya and fibers. Nppositive perikarya are found in the triangular nucleus of the septum. Np fibers join the stria terminalis (ST) at the level of the anterior hypothalamus, and course medially in the ST to the central nucleus of the amygdala. Np fibers are found in the brain stem and spinal cord. Fine caliber Np fibers from the suprachiasmatic nucleus ascend to the medial dorsal thalamus and lateral septum. The presence of Np within neurones implies the presence of either vasopressin or oxytocin. Np-positive fibers in extrahypothalamic sites may interact with non-neurosecretory neurones involved in neuroendocrine regulation, or may serve as yet unknown functions.

The influence of faunal condensation and mixing on the preservation of fossil benthic communities

Abstract: Fursich. Franz Theodor 1978 07 IS: The influence of faunal condensation and mixing on the preservation of fossil benthic communities. Lethaia, Vol. 11, pp. 243–250. Oslo. ISSN 0024–1164. Condensation phenomena caused by environmental, biotic, or diagenetic factors are widespread in the fossil record, especially in shallow shelf sediments, and may alter the composition of ancient communities. Even without large-scale transport being involved, often only time-averaged seres will be available for palaeosynecological studies. This should be kept in mind when community analysis of such shell accumulations is attempted.

Psychoacoustical tuning curves in audiology

Abstract: The correlation between classic masking patterns and psychoacoustical tuning curves is discussed quantitatively. A simplified method to measure such tuning curves in clinical use is described. They are shown to be insensitive to the frequency dependence of the hearing loss. Tuning curve data of six different groups including normal and hard-or-hearing observers are given: normal hearing, conductive hearing loss, degenerative hearing loss, noise-induced hearing loss, otosclerosis and Meniere's disease. The resulting tuning curve data indicate that the frequency resolving power of the four groups mentioned last is greatley reduced but not completely absent, especially in the range of greater hearing loss. The correspondence between the frequency-resolving power measured by the tuning curve method and the result of speech discrimination tests is demonstrated. The measured data indicate that more than 50% of the patients with otosclerosis show reduced frequency selectivity although otosclerosis is commonly regarded as a conductive hearing loss.

Intracellular study of electrical activity of Auerbach's plexus in guinea-pig small intestine.

Abstract: Intracellular recording revealed two general categories of ganglion cells in Auerbach's plexus. The characteristics of one category were relatively low resting potentials, high input resistance, discharge of spikes throughout a depolarizing current pulse, stimulus-evoked synaptic potentials and spontaneous electrical activity. Characteristics of the second category were high resting potentials, low input resistance, spikes only at the onset of a depolarizing current pulse and long duration hyperpolarizing after-potentials. Responses to extracellular electrical stimulation of the ganglia and interganglionic fiber tracts consisted of electrotonic spread of spikes from the processes to the cell soma, somal action potentials and depolarizing and hyperpolarizing responses that were probably EPSPs and IPSPs. Some of the neurons which received excitatory synaptic input responded with a prolonged train of spikes that outlasted by many seconds the duration of the stimulus to the fiber tract. Spontaneous electrical activity consisted of single EPSPs, patterned bursts of spikes that originated in the cell processes and spread electrotonically to, the recording site, IPSPs and action potentials. The burst-type activity showed periodic conversions from a burst pattern to a trainlike pattern of continuous discharge. Spontaneous discharge of single action potentials was superimposed upon a background of continuous synaptic input to the cell. Spontaneously occurring hyperpolarizing potentials were converted to depolarizing potentials when the membrane was hyperpolarized by current injected through the recording electrode.

Longitudinal studies of plasma aldosterone, corticosterone, deoxycorticosterone, progesterone, 17-hydroxyprogesterone, cortisol, and cortisone determined simultaneously in mother and child at birth and during the early neonatal period. I. Spontaneous delivery.

Abstract: In order to obtain the still lacking reference data of individual plasma steroids in the immediate postnatal period needed for the assessment of adrenocortical function in various neonatal maladaptation syndromes, aldosterone (A), corticosterone, deoxycorticosterone (DOC), progesterone (P), 17-hydroxyprogesterone (17-OHP), cortisol, and cortisone were simultaneously followed in the same human newborn in a single 250–500 µl peripheral plasma sample obtained at constant times during the first week of life using a mechanized Sephadex LH-20 multicolumn chromatography and standardized RIAs. Mean concentrations in 12 spontaneously delivered full term newborns of either sex and in paired umbilical (UV) and peripheral maternal (MV) venous plasma are given in the table. Besides significant maternoumbilical gradients in each steroid, DOC, P, 17-OHP, and cortisone, originating predominantly from the fetoplacental unit, disappear rapidly with steadily increasing half-lives. A, corticosterone, and cortisol, however, r...

Preparation of freeze-dried cryosections for quantitative X-ray microanalysis of electrolytes in biological soft tissues

Abstract: A procedure is described which allows the evaluation of wet weight concentrations of diffusible substances in biological soft tissue on a cellular level by the use of energy dispersive X-ray microanalysis. Epithelia of frog skin and toad urinary bladder were used to prepare freeze-dried cryosections without the use of chemical fixatives, cryoprotectants, floating solutions or coating materials. The specimens were shock-frozen inl-propane (−180°C), cryosectioned (−80°C), sandwiched between collodion films and freeze-dried (−80°C). The analysis was performed in a scanning electron microscope at an acceleration voltage of 15 kV, probe current of 0.5 nA, using scanning areas of 1–2 μm2. The spatial resolution power using 1–2 μm thick sections was about 0.7 μm. In a superficial layer of about 30 μm the analysis was found not to be influenced by tissue damage due to ice crystal formation. The mass loss during electron bombardement was restricted to constituents of the organic matrix (30%). No changes of characteristic radiation were observed for Na, K and Cl. Albumin standards, containing electrolyte concentrations in the range of biological interest, revealed linear calibration curves. To obtain reliable wet weight concentrations, the characteristic X-rays of the tissue were compared to those of an internal standard which was applied to the specimen prior to freezing and analysed simultaneously.

Slow synaptic excitation mediated by serotonin in Auerbach's plexus.

Abstract: THE application of low concentrations of substance P to guinea-pig myenteric neurones has been reported by Katayama and North to produce depolarisation associated with an increase in input resistance and augmented excitability1. On this basis, they suggested that substance P may be involved in the production of the slow excitatory postsynaptic potential (e.p.s.p.) which can be evoked in myenteric neurones by electrical stimulation of the interganglionic connectives2. In this report, we show that application of serotonin (5-HT) mimics the slow e.p.s.p., and present several lines of evidence which suggest that 5-HT is a more likely candidate for the neurotransmitter of the slow e.p.s.p.

A Role of Mitochondrial Glutathione Peroxidase in Modulating Mitochondrial Oxidations in Liver

Abstract: 1 The inhibitory effect of t-butyl hydroperoxide on O2 uptake by perfused rat liver and by isolated hepatocytes was investigated with isolated mitochondria. 2 O2 uptake by mitochondria oxidizing the ketoacids, 2-oxoglutarate and pyruvate, was substantially decreased upon addition of t-butyl hydroperoxide, that of isocitrate was only slightly decreased, and that of succinate and of 3-hydroxybutyrate was practically unchanged. The reduction product of the hydroperoxide, t-butyl alcohol, showed no effect. The inhibitory effect of the hydroperoxide was reversed upon addition of dithioerythritol, a thiol reductant. The inhibitory effect of the hydroperoxide was mimicked by the penetrant disulfide, cystamine, and by the thiol-oxidizing agent, diamide. 3 Mitochondrial extracts from rats fed a selenium-deficient diet were shown to have virtually no measurable GSH peroxidase activity. The hydroperoxide had almost no inhibitory effect on 2-oxoglutarate-dependent O2 uptake in mitochondria from selenium-deficient rats. 4 These observations demonstrate effects of GSH peroxidase activity in the mitochondrial matrix on the pattern of substrate oxidations, possibly with the ketoacid oxidases, dependent on coenzyme A and lipoamide, as main target sites. In view of the known steady-state formation of mitochondrial O2− and H2O2, a connection between the resulting oxidation of mitochondrial GSH and NADPH and the regulation of mitochondrial substrate oxidations is proposed.

Deoxyribonucleic acid reassociation in the classification of coagulase-positive staphylococci

Abstract: DNA-DNA reassociation studies were performed with coagulase-positive staphylococci belonging to the biotypes A, B, C, D, E and F. These studies present genetic evidence for the existence of at least two distinct species within this group of organisms. The common Staphylococcus aureus strains were represented by organisms from biotypes A to D, and their DNA revealed over 80% nucleotide sequence homology under restrictive conditions. Less than 15% DNA homology was detected between strains from biotypes A to D (S. aureus) and those from biotypes E and F. The DNA of organisms from either the biotypes E or F displayed over 70% homology. Together, both biotypes are considered to represent the species S. intermedius. However, DNA homology values dropped to 50--65% between strains from different biotypes. This may justify the separation of S. intermedius biotypes E and F on a subspecies level.