Showing papers by "University of Göttingen published in 1971"

The calcite-aragonite transition, reinvestigated

Abstract: The calcite-aragonite equilibrium has been investigated between 200 and 600° C both in a carefully calibrated hydrothermal apparatus and in a piston-cylinder device of high precision. The equilibrium pressure is 5 kb at 180° C, 7 kb at 300° C, 9 kb at 400° C, and 11 kb at 480° C. The calcite-aragonite transition boundary which has been bracketed is continuously curved between 300 and 500° C and is more or less straight above and below this temperature range. It is shown that the calcite I-calcite II reaction is probably a second (and not a first) order transition. The experimental result shows that aragonite may already be formed out of calcite at a depth of 15 km if the temperature is not much higher than 100° C. The calcitearagonite and the albite-jadeite-quartz curves intersect at about 750° C and 20 kb. There is a P-T-field (up to 3.5 kb broad) where aragonite and albite coexist.

Gastrin and G-cells in the antral mucosa of patients with pernicious anaemia, acromegaly and hyperparathyroidism and in a Zollinger-Ellison tumour of the pancreas.

Abstract: . In extracts of human gastric biopsies gastrin has been estimated with an immunochemical method. In the same biopsies G-cells have been localized with an immunohistological method using peroxidase-labelled antibodies and the endocrine cells investigated electron-microscopically. Gastrin and G-cells could be found regularly in the antral mucosa and only in insignificant amounts or not at all in the fundic mucosa of six normal persons. With the same methods gastrin and G-cells could be demonstrated in the antral mucosa of rats and guinea-pigs. The gastrin content of the antral mucosa of six patients with pernicious anaemia and achlorhydria with elevated serum gastrin levels was more than 20 times higher than in the controls and the G-cells were significantly more numerous. Besides hyperplasia of the G-cells, increased secretory activity was found electron-microscopically. The gastrin release from the G-cells seems to take place mainly via intracellular dissolution of the granule content within the membranous sacs. Although the number of other endocrine cells was increased in pernicious anaemia the ultrastructural identity of the G-cells could be established by comparison with the cells of a Zollinger-Ellison tumour. This tumour contained gastrin and gave a positive immunohistological reaction for this hormone. Also, the fundic mucosa of patients with pernicious anaemia contained gastrin and G-cells, but considerably less than the antral mucosa. Hyperplasia of G-cells was found in six cases of acromegaly, four of which also had a significantly increased gastrin content of the antral mucosa. This finding suggests a trophic function of the hypophysis, especially growth hormone, on the G-cells. Hyperplasia of the G-cells in the antral mucosa of three patients with primary hyperparathyroidism and increased gastrin content in two of the three cases also suggest a trophic function of the serum calcium level on the G-cells.

On the neurons and synapses of the lateral geniculate nucleus of the monkey, and the effects of eye enucleation.

Abstract: Two neuron types are distinguished by electron microscopy in the lateral geniculate nucleus (LGN) of the monkey-a large cell (P cell) interpreted as a geniculostriate relay cell, and a small cell (I cell) interpreted as an inhibitory interneuron. The I cell, distinguished by its small size, infolded nucleus, small mitochondria, cilium and small granular bodies, forms about 10% of the total neuron population. It could not be determined whether this cell has an axon, but its dendrites, which contain aggregates of flattened vesicles, are thought to form a proportion of the “F processes”, profiles which are post-synaptic to the retinal (RLP) axons and presynaptic to the dendrites of the P cells. The small dark (RSD) axon terminals of unknown origin contact the dendrites of both cell types. After eye enucleation the P cells of the affected laminae of the LGN shrink and partially withdraw their dendrites from the neuropil. By 29 months' survival, they have only a narrow cytoplasmic rim around the nucleus. A necrotic process also occurs, affecting fine dendrites by 22 days and large profiles by 45 days, but it is not clear whether whole cells are destroyed by this process. At 45 days the I cells are commonly seen to form somatodendritic synapses. The appearance of these synapses is interpreted as the result of a withdrawal to the soma of the presynaptic dendrites. It is concluded that the I cells are probably inhibitory interneurons subject to excitation and presynaptic inhibition by the RLP and RSD axons, and a diagram is presented to demonstrate the possible significance of these connections for the transmission of information through the LGN.

Die augen der Araneae

Abstract: This paper is a condensation of our knowledge on the eyes of the Araneae with respect to anatomy and ontogeny. After the addition of new observations, generalizations are allowed at the present state of our knowledge. On the basis of the structure of the eyes a change in a part of the system of the Araneae has to be proposed.

Stabilitätsbeziehungen von Prehnit- und Pumpellyit-haltigen Paragenesen

Abstract: This investigation was undertaken to find the typical conditions for the formation of low-grade metamorphic rocks in which prehnite and/or pumpellyite (± actinolite, chlorite, epidote, and quartz) occur as characteristic minerals. In the p, t diagram the slope of the equilibrium curve prehnite + chlorite + H2O=pumpellyite + actinolite + quartz is negative; the slope of the equilibrium curve pumpellyite + chlorite + quartz=epidote + actinolite + H2O is positive. The point of intersection of the two equilibrium curves is an invariant point. The relative positions of the six equilibrium curves surrounding the invariant point were found by applying Schreinemakers's analysis. Experimental results show that the paragenesis prehnite-pumpellyite-chlorite-quartz is stable at 2 kb up to 345±20 °C, and at 7 Kb up to 260±20 °C. The paragenesis actinolitechlorite-pumpellyite-quartz occurs only at pressures greater than 2.5±1 kb. It is stable at 7 kb in the strongly pressure-dependent temperature range 260±20 °C to 370±20 °C. The paragenesis actinolite-chlorite-epidote-quartz, typical of the greenschist facies, may occur at pressures of 2–3 kb at temperatures of at least 350±20 °C. This temperature limit is only slightly changed with increasing pressure.

Comparison of Subacute Sclerosing Panencephalitis and Measles Viruses: an Electron Microscope Study

Abstract: The ultrastructure of CV-1 cells infected with subacute sclerosing panencephalitis (SSPE) viruses was compared with that of CV-1 cells infected with the wild or Edmonston strain of measles virus. Both SSPE viruses and the measles viruses produced two types of nucleocapsid structures: smooth filaments, 15 to 17 nm in diameter, and granular filaments, 22 to 25 nm. The smooth and granular filaments produced by SSPE and measles virus did not differ in appearance. In CV-1 cells infected with SSPE viruses, smooth filaments formed large intranuclear inclusions and granular filaments occupied a large area of the cytoplasm, but always spared the area under the cell membrane. Particles budding from the surface of these cells contained no nucleocapsids. In CV-1 cells infected with measles virus, only small aggregates of smooth filaments were seen in the nuclei. Granular filaments in the cytoplasm predominantly occupied the area under the cell membrane, and were aligned beneath the cell membrane in a parallel fashion and assembled into budding particles. These differences between SSPE and measles virus may be regarded as quantitative, but they do distinguish SSPE viruses from measles virus. Moreover, the formation of large nuclear inclusions filled with smooth filaments appears to be a characteristic process of SSPE, but not of measles, since this type of inclusion is invariably seen in SSPE brain tissues, brain cultures derived from them, and CV-1 cells infected with SSPE viruses.

Analysis of the inhibitory effect of biguanides on glucose absorption: inhibition of active sugar transport.

Abstract: The effect of biguanides (phenethylbiguanide, butylbiguanide and dimethylbiguanide) on absorption of actively transported sugars was examined by incubating rings of hamster small intestinein vitro. Biguanides inhibited transport of D-glucose, D-galactose and 3-0-methyl-D-glucose but had no effect on the transport of D-fructose. Inhibition of D-xylose transport could only be demonstrated if concentrations far below halfmaximal saturation concentration (Km) were used (10−5M), but not with concentrations approaching concentrations during a D-xylose tolerance test (18 mM). Formation of lactate by intestinal tissue was increased in presence of biguanides using D-glucose or D-fructose as substrates. The minimal inhibitory concentrations on transport of D-galactose were 10−3M for phenethylbiguanide, 2×10−3M for butylbiguanide and 6×10−3M for dimethylbiguanide. The metabolite of phenethylbiguanide, 1-(4-hydroxy-β-phenethyl)-biguanide, did not affect glucose uptake but increased glucose metabolism to some extent. The demonstrated inhibition of active intestinal transportin vitro may be the mechanism for the decreased absorption of glucose observed by other authorsin vivo in man and animals after biguanides.

The Regulation of Pyruvate Kinase

Abstract: Publisher Summary This chapter discusses the molecular and kinetic properties, and the physiological significance of pyruvate kinase. From a thermodynamic consideration, these enzymes are especially suited for a control of glycolysis, because they catalyze unidirectional steps driving the metabolic flux into one direction. The combined action of the key enzymes of glycolysis and gluconeogenesis at the control points would allow futile cycles, resulting in the hydrolysis of energy-rich phosphate—an energy-wasting process. Additional regulatory properties of the key enzymes of glycolysis should therefore be expected in tissues that are able to carry out both glycolysis and gluconeogenesis, allowing an opposing control of both metabolic processes. Changes of pH in physiological range would, in addition, allow an opposing control of gluconeogenesis and glycolysis at the level of pyruvate kinase and pyruvate carboxylase reactions. Changes of the pH would not only control pyruvate kinase at suboptimal concentrations of PEP and antagonize the negative control of pyruvate kinase by ATP and alanine, but also control in an opposing way, at suboptimal levels of acetyl-CoA pyruvate carboxylase, the enzyme acting in direction of PEP-synthesis. This relationship adds strong support to a physiological significance of both the intracellular pH and acetyl-CoA in the control of glycolysis and gluconeogenesis in liver.

Studies on the substructure of togaviruses. II. Analysis of equine arteritis, rubella, bovine viral diarrhea, and hog cholera viruses.

Abstract: The viruses of equine arteritis, rubella, bovine viral diarrhea and hog cholera have been concentrated and purified. In preparations negatively stained with uranyl acetate they appeared as roughly spherical particles about 60 nm across. Within their envelopes isometrical cores were detected after spontaneous disruption or upon pretreatment; they are considered to be the viral nucleocapsids. The lower coefficients of variation calculated for the nucleocapsids as compared with those of the respective virus particles indicate that the pronounced heterogeneity in virion size must be attributed to the envelope. Ringlike morphological subunits observed on the surface of the spherical nucleocapsids and the presence of centra] core components suggest that the four viruses should be classified as togaviruses (lipid-containing RNA viruses with cubic symmetry of the nucleocapsid), together with arbo-A-viruses. The bovine viral diarrhea and hog cholera viruses differ from the other viruses studied in their lower sedimentation and density values, their lesser nucleocapsid diameters and an unusual “rosary” envelope structure. A further subdivision of the togavirus group is discussed.

Studies on the genetic heterogeneity of diabetes mellitus

Abstract: In 552 adult-onset diabetics the frequency of diabetes among the brothers and sisters was calculated employing an age correction. The siblings of diabetics have a chance of 25.8% of becoming diabetic up to the age of 85 years. Siblings of those diabetics with a high degree of overweight and of female diabetics with many pregnancies have a significantly lower chance of becoming diabetic than siblings of diabetics without overweigth and with no or few pregnancies. This relationship is only found in diabetics with oral or dietetic therapy, but not in diabetics with insulin therapy. From these observations it can be concluded that genetic heterogeneity exists between diabetics with and without the need of insulin, and, further, within the group of non-insulin-treated diabetics between those with and without additionl pathogenetic factors, such as overweight or multiparity.

Proteins of the sieve-tube exudate of Cucurbita maxima.

Abstract: Sieve-tube exudate which appears on cut surfaces of stems of Cucurbita maxima as distinct droplets has been depicted in electron micrographs of longitudinal sections of the phloem. The exudate, which was produced from mature sieve tubes only, contained filaments of P-protein, but no mitochondria or vesicles of endoplasmic reticulum. The water-soluble part of the exudate contained at least 12 proteins, as shown by disc-electrophoresis. Enzymic activity was found for peroxidases, acid phosphatases, and aldolases. Color tests and assays for other enzymes, including ATPase, fructokinase, several dehydrogenases, and UDP-glucose: D-fructose-2-glucosyl transferase, gave negative results. With repeated cutting of a stem, the protein content of the exudate increased, while the amount of exudate decreased.

Characterizing Moišezon spaces by almost positive coherent analytic sheaves

Abstract: An irreducible normal compact complex space X is a Moigezon space if the transcendence degree of the field of meromorphic functions on X is equal to the complex dimension of X. In a joint paper [7] Grauert and the author introduced the notion of\" quasi-positive\" coherent analytic sheaves on complex spaces and proved a \"vanishing theorem\" for such sheaves on Moigezon spaces which is analogous to the vanishing theorem of Nakano [18] for positive vector bundles on compact complex manifolds. It is well known that a normal compact complex space is projective algebraic if and only if it carries a weakly positive vector bundle (in the sense of Grauert [6]). Therefore, it is a natural conjecture that an irreducible normal compact complex space X is a Moi~ezon space if and only if there exists a (torsion free) coherent analytic sheaf 5P on X which is weakly positive almost everywhere. This paper is a first but very modest step forward to the proof of this conjecture. First of all we give the sentence \"a vector bundle E over a complex space X with singularities is weakly positive almost everywhere\" an exact meaning and call such vector bundles almost positive. It has been shown by Griffiths [8] and Kobayashi and Ochiai [13] that there are also precise vanishing theorems for almost positive vector bundles on compact K~ihler manifolds (cf. w 1). We then investigate in w 2 the observation of Rossi [-19] that coherent analytic sheaves can be made free (modulo torsion) by proper modifications, i.e.: If 5 ~ is a coherent analytic sheaf on an irreducible compact complex space X then there exists a (minimal) proper modification q~: 2 + X where X is an irreducible compact complex space such that the torsion free preimage 5~=5Po q~ = ~o* 5P/torsion (q)* 5 p) is locally free. We shall show that Rossi's construction is the (unique) solution of a universal mapping problem and that it coincides with monoidal transformations if 5 p is an ideal sheaf on X. In w 3 we define a sheaf5 P on X to be almost positive if the locally free sheaf 5P is almost positive in the sense of w 1, and prove a vanishing theorem for almost positive coherent analytic sheaves on Moi~ezon spaces. The methods are the same as in [7]. The last paragraph is devoted to the connection between Moigezon spaces and almost positive sheaves. We show: Every normal Moi~ezon space X carries

Measurements of the Ionic Conductivity of α‐Silver Iodide Crystals in the Frequency Range from 1010 to 1013 Hz Using Microwave Techniques and Fourier Spectrophotometry

Abstract: Electrical conductivity and dielectric constant of α-Agl at frequencies between 1010 and 1013 Hz are measured at various temperatures. In the microwave range the cation conductivity of α-AgI decreases with increasing frequency, and a relative maximum of the conductivity is found at ca. 30 GHz. In the far infrared α-AgI has a very broad absorption band between ca. 2 · 1011 and 6 · 1012 Hz. Elektrische Leitfahigkeit und Dielektrizitats-Konstante des α-AgI wurden im Frequenzgebiet von 1010 bis 1013 Hz bei verschiedenen Temperaturen untersucht. Im Mikrowellengebiet wird ein Ruckgang der Kationen-Leitfahigkeit beobachtet, dem bei etwa 30 GHz ein relatives Leitfahigkeitsmaximum uberlagert ist. Im fernen Infrarot hat α-AgJ eine sehr breite Absorptionsbande von ca. 2 · 1011 bis 6 · 1012 Hz.

Die konjugative Wechselwirkung zwischen π- und Walsh-Orbitalen: Das Photoelektron-Spektrum des Homofulvens.

Abstract: Analysis of the photoelectron spectrum of homofulvene (1) (spiro [2.4] hepta-4,6-diene) confirms the conclusions previously drawn concerning the direct conjugation between π-and Walsh-orbitals. It is shown that the resonance integral (4) appropriate for the semi-quantitative interaction of these orbitals amounts to −1.9 eV, i.e. nearly the value for conjugating π-orbitals (β = −2.4 to −2.5 eV). This explains the close analogy between the photoelectron spectrum of 1 and that of fulvene.

Die Reaktion von atomarem Wasserstoff mit Hydrazin

Abstract: Die Reaktionen von O, H, D und N-Atomen mit Hydrazin wurden zwischen 243 und 463 °K in einem isothermen Stromungssystem mit hoher Zeitauflosung untersucht. Stabile und instabile Reaktanden konnten durch gleichzeitige Anwendung von ESR und Massenspektroskopie mit hoher Empfindlichkeit nachgewiesen werden. Ein modifizierter Einlas (gekreuzte Freistrahlen) fur das Massenspektrometer ermoglichte eine unmittelbare Bestimmung der Produkte der Primarreaktionen. Fur die Geschwindigkeit des Elementarschrittes Ist [O]o/[N2H4]o > 4 so werden in Folgereaktionen im wesentlichen H-Atome, N2, NO und O2 gebildet. Ist [O]O/N2H4[O] < 2, so kommt es daneben zur Bildung von NH3, N3H und N4H4. Fur die Reaktionen Fur die Geschwindigkeit der Reaktion von Stickstoffatomen mit N2 H4 erhalt man bei 293 °K einen Wert von 7,5.1010 [cm3/ mol· sec]. The reactions of O, H, D and N atoms with hydrazine were studied between 243 and 463 °K in a fast flow reactor. Stable and unstable products were measured with high sensitivity simultaneously by ESR and mass spectroscopy. The primary products of the elementary reactions were determined directly from experiments with crossed nozzle beams attached to the T.O.F. mass spectrometer. The rate of the reaction At a ratio [O]o/[N2H4O] > 4 the main products from subsequent reaction steps are : H-atoms, N2, NO and O2 whereas at [O]o/[N2H4]0 < 2 further products as NH3, N3H, N2H4 are formed. The rates of the reactions and the rate for the overall reaction of nitrogen atoms with hydrazine 7.5.1010 [cm3/mol.sec] (T = 293 °K).