Showing papers by "University of Vienna published in 1973"

Primary intracranial germ cell tumours.

Abstract: A histological study has been made of a retrospective series of 17 primary intracranial germ cell tumours found in a collection of 3550 intracranial neoplasms (incidence of 048%) All, except for two differentiated teratomas (one extracerebral in a neonate and another in the lateral ventricle), were situated in the midline in persons aged 5 to 37 years (13 males, 4 females) 12 tumours were located in or originated from the (para)pineal region, two of them also invaded the hypothalamus, while three germinomas occupied the retrochiasmal (supra/intrasellar) region without pineal involvement There were 11 rather pure tumours (7 germinomas, 4 teratomas of various differentiation) and six “mixed” neoplasms (2 germinomas with teratoid areas, 3 embryonal carcinomas containing elements of endodermal sinus tumour, choriocarcinoma and germinoma, and one teratocarcinoma with endodermal sinuses) Only one case showed prominent features of endodermal sinus tumour, but characteristic elements of this type were present in four other “mixed” tumours All germinomas and germinomatous parts of mixed neoplasms showed an inflammatory reaction of varying intensity, in 6 cases associated with multinucleated giant cells, which may be related to the prognosis of these tumours (one patient with hypothalamic germinoma is alive 6 years after radiotherapy) The close structural similarities between the various types of intracranial and gonadal dysgerminomas and their frequent combination within the same tumour support the concept of a common histogenesis of germ cell tumours regardless of their site of origin Difficulties of classification may arise from the rather frequent occurrence of “mixed” germ cell neoplasms

Sponge burrowing: Fine structure of Cliona lampa penetrating calcareous substrata

Abstract: Cliona lampa Laubenfels (Porifera: Hadromerida), a common burrowing organism in Bermuda, has been used to study the method of sponge penetration into calcareous objects. To progress beyond the results obtained by previous authors, electron-microscope techniques, in addition to light-microscope observations, were employed. Burrowing patterns, fine structure of the tissue-substratum interface and of calcareous fragments removed by sponge activity are described on the basis of scanning electron microscopy. Cell types and cytological features have been identified by light and transmission electron microscope. One cell type of archeocyte origin is demonstrated; it carves out chips of calcium carbonate (and conchiolin) by means of filopodial extensions and etching secretions. The cells undergo plasmolysis during this process; the substratum chips are expelled through the exhalent canal system. It is calculated that only 2 to 3% of the eroded material is removed in solution.

The Biomass and Distribution of Organisms in Lake George, Uganda

Abstract: Ninety-five per cent of the total biomass in the open water of Lake George, a shallow equatorial lake, is phytoplankton. The biomass of this and the other major groups of organisms are given and compared with some figures from other lakes. Apart from the phytoplankton, standing crop levels in Lake George are not high and may be exceeded, although only for short periods, by organisms in temperate waters. Levels in Lake George, in contrast, fluctuate little throughout the year. The specific composition of the open water community is described and shown to be dominated by blue-green algae and three herbivores which utilize them as a food source: one cyclopoid copepod and two fish. The reasons why these and other species make up the open water community in Lake George are discussed and also possible factors which may limit some of the animal populations to the levels observed. Both the phytoplankton and the zooplankton exhibit a concentric pattern of distribution across the lake. Concentrations are highest in the centre and this may be attributable to the circular movements of the water mass which result from the shape of the basin and the wind regime. It might also be correlated with grazing effects since the fish population, which also shows a concentric distribution of biomass, has its highest concentrations in the inshore regions and its lowest in the centre. The distribution and species composition of the benthos is determined primarily by the nature of the substrate. In the open water area the bottom consists of soft, unstable, deoxygenated mud which contains few species. Inshore the substrate is firmer and more varied and carries a greater density and variety of animals. These are preyed upon by a greater variety of fish, particularly species of the cichlid genus Haplochromis, than are found in the mid-lake area. The inshore region is short, due to the regular shape of the lake basin, and narrow, but provides a variety of habitats in contrast to the homogeneity of the mid-lake area. The lake is fringed in many places by papyrus swamp, the Nile cabbage floats on the surface of the water but there is no submerged aquatic vegetation.

Ecological Stability in a Shallow Equatorial Lake (Lake George, Uganda)

Abstract: The ecological stability of Lake George is illustrated by the relatively small biomass fluctuations that occur in the fauna and flora of the lake. For the phytoplankton it is shown that the gradient of these oscillations is within the range depicted by a specific rate of population increase of +0.05 to -0.05 day$^{-1}$. The relative stability of the phytoplankton community is discussed in the terms of a mathematical model (Talling 1957, 1971) which interrelates the variables, photosynthesis, respiration, biomass and the underwater light climate. Examples of the interrelationship, and the extreme susceptibility of either a positive or a negative increase rate to diurnal environmental changes, are drawn from both long and short term measurements in Lake George. The optical characteristics of the water column are shown to be very dependent upon the mixing regime sustained over the previous 24 h. The occurrence of negative or positive increase rates is dependent not only upon the incident radiation but also upon the wind induced turbulence. It is shown that, given measurements of the rates of photosynthesis and respiration and the other variables included in Talling's model, the biomass at which the Lake George phytoplankton will stabilize is predictable. Although light is likely to limit photosynthesis under all circumstances in Lake George, it is demonstrated that a more favourable photosynthetic response to the light climate may be induced by nutrient enrichment of the nutrient-poor phytoplankton. Because nutrient enrichment can induce increased photosynthetic capacity values, the rates of nutrient supply are thought to be major factors in controlling the ecological stability of the phytoplankton. The mixing regime of the lake is of paramount importance in the decomposition of the sediments and the rate of nutrient release from them. The importance of the nutrient recycling via zooplankton excretion is compared with the total input of nitrogen and phosphorus to the lake. That the ecological stability of the lake is a delicately balanced equilibrium between climate and biota is illustrated by calculations on the oxygen budget of the water column, and by the occurrence of fish-kills. The general characteristics of the lake are discussed in the context of the problems associated with eutrophication.

Relations between metamorphism and orogeny in a typical section of the Indian Himalayas

Abstract: A comprehensive geological and petrological investigation has been undertaken in an area of about 10 000 km2 in the Indian Himalaya (S-Lahul, Himachal Pradesh). The development of mineral assemblages in metamorphic rocks of medium grade is considered to be a dominant Alpine event, although almost exclusively Paleozoic and Precambrian rocks have been involved. The Barrowian type of this metamorphism, ranging from the anchi- to the sillimanite zone, took place under the elavated T-gradient of about 4°C/100 m. It is suggested that “normal” geothermal conditions prevailed only in the outermost zone of this orogenic belt. In the Late Tertiary this metamorphic series has been moved as a huge nappe upon the Lower Himalaya. During this process a unique feature of reverse metamorphism has been formed. It can be shown that this feature was caused by a combination of metamorphism and very rapid tectonic movements.

Zur Struktur der Defekt-Mangansilicide Kristallstruktur von Mn27Si47

Abstract: The atomic parameters of Mn27Si47 have been determined.ZusammenfassungDie Kristallstruktur eines weiteren Defekt-Mangansilicids (Mn27Si47) wird bestimmt.

Die Kristallstruktur von Bi2O2Se

Abstract: Bi2O2Se crystallizes in the (Na0.25Bi0.75)2O2Cl type structure (space group I4mmm−D 4h 17 ;a=3.891 A,c=12.213 A). The crystal chemical properties of the bismuth oxiselenide are discussed in connection with the other compounds having this structure type.

Hypertrophy of the inferior olives. Report on 29 cases.

Abstract: A report is given on 29 cases of olivary hypertrophy of different origin with special reference to the quality and topistic distribution of olivary degeneration in relation to the dating and site of the primary lesion. All except one case of hypertrophic degeneration of the inferior olive resulted from injury to the dentato-olivary pathway; 13 were associated with an isolated lesion of this pathway; while in 15 cases bilateral olivary hypertrophy was secondary to multiple injury to the afferent olivary pathway. There were 12 cases of primary cerebrovascular disease, 13 cases of head injury and other lesions resulting from transtentorial herniation, and four tumours of the brain stem, one of which showed “blastomatous” olivary hypertrophy different from the usual olivary response to deafferentation. Early vacuolation of olivary neurons was seen 12 to 20 days after injury to the dentato-olivary pathway, while after longer survival olivary hypertrophy characterized by degeneration and enlargement of neurons and astroglia was associated with secondary degeneration of other parts of the dentato-olivary pathway and olivo-cerebellar tract. Correlative studies of the distribution of primary lesions and of the pattern of ensuing degeneration of inferior olives and other related structures confirmed and further defined the previously known topistic organization of the dentato-olivary pathway and the somatotopic relations between the dentate nuclei and contralateral inferior olives and the other structures involved in this neuronal circuit. The unique features of olivary hypertrophy related to transneuronal degeneration in response to deafferentation are compared with experimental data and other rare forms of olivary enlargement of blastomatous origin. Palatal myoclonus was only reported in 2 patients with old brain stem infarctions.

Metronidazol encephalopathy in rats

Abstract: Trichomonacidum Metronidazole in daily doses of 600 and 800 mg/kg was applicated per throat-sound to six week old SPF-Wistar-rats each day for six weeks. Increase of body-weight, food-demand and the usual clinical watch-over showed no difference to controll-group. Already three days after begin of application behaviour-research showed motion-changes, especially balance-disturbance of femal rats. Measure of running-speed proved no changes. Histological sections of the perfused CNS after treatment with 800 mg/kg Metronidazole showed relatively sharp bounded, usually symetric lesions in the nuclei vestibularis and cochlearis, in the nuclei of the cerebellar roof, paramedial in the colliculus anterior and in the superior olive. These alterations are qualitatively and topographically comparable to CNS-lesions in rats caused by B1-avitaminosis and lesions seen in Wernicke's-encephalopathy in adults and children. The initial and progressed stages of such an experimental CNS insult in rats open numerous possibilities to clear up the pathogenesis of this and other spongiform dystrophies.

[Correlative morphometric studies of cerebral arteries in Binswanger's encephalopathy and hypertensive encephalopathy (author's transl)].

Abstract: A morphometrical study was performed on subarachnoidal and hemispheral white matter arteries of 7 cases (5 pure and 2 mixed forms) of Binswanger's encephalopathy (BE) and of 8 cases of common hypertensive encephalopathy and intracerebral hemorrhage (HDE). A control group of 10 cases included 2 cases of CO-leukoencephalopathy and 1 case of Pelizaeus-Merzbacher's disease. The data of the thickness of media and the radius of the measured arteries were submitted to linear regression analysis. All cases of BE and HDE showed a distinct media hypertrophy of subarachnoidal and white matter arteries which was not present in the control group. A morphometrical difference between BE and HDE was found only in small white matter arteries, where the media in BE-cases was significantly thicker than that in HDE. No difference was found between pure and mixed forms of BE. Based on these findings it is suggested that the strikingly prominent media hypertrophy of small white matter arteries in BE depends not only on hypertension but also on a pathologically increased reactivity for hypertension. Redistribution of the cerebral blood flow in form of a vascular “counter steal” from cortical to white matter arteries, based on the specific angioarchitecture of the cerebrum, may contribute to the well-known histopathological features of BE.

Hot-Electron-Phonon Interaction in the Nonparabolic Conduction Band of Degenerate InSb at 4.2 K

Abstract: Adopting the Kane model of the nonparabolic conduction band of InSb, calculations of the energy-loss rates of the electrons to acoustic modes via deformation potential and piezoelectric coupling and to polar optical modes are performed. Use is made of matrix elements which take into account $p$-function admixture and static screening of the electron-phonon interaction. The applicability of this theoretical approach to experiments at 4.2 K in strongly degenerate $n\ensuremath{-}\mathrm{I}\mathrm{n}\mathrm{S}\mathrm{b}$ is examined. Measurements of the electric-field-dependent amplitudes of the Shubnikov\char22{}de Haas effect with $B\ensuremath{\parallel}j$ are used to determine the dependence of the electron temperature on the electric field up to 1.7 V/cm. Theoretical values of the energy-loss rates are found on averaging over the Fermi distribution at an elevated electron temperature ${T}_{e}$. A combination of deformation-potential scattering and piezoelectric scattering accounts for the energy-loss rate below ${T}_{e}=12$ K. A value of the deformation-potential constant of 6.9 \ifmmode\pm\else\textpm\fi{} 0.4 eV is used to fit the calculated energy-loss rates to the experimental data. Above ${T}_{e}=24$ K, polar-optical-phonon scattering is the dominant mechanism. Between 12 and 24 K, there remains a difference between experiment and theory which is attributed to a two-phonon-scattering process.

Über Aminosäuren und Peptide, VIII. Asymmetrische Synthese aromatischer α‐Aminosäuren und N‐Methyl‐α‐aminosäuren. — Synthese von L‐Dopa. — Über die katalytische Hydrierung ungesättigter Cyclodipeptide

Abstract: Die katalytische Hydrierung von Arylidenderivaten des Glycyl-L-prolin-anhydrids wie 9a–e verlauft mit hoher asymmetrischer Induktion. Diese Reaktion, gefolgt von der sauren Hydrolyse des gesattigten Dioxopiperazins, kann zur Darstellung aktiver aromatischer Aminosauren, wie L-Dopa oder L-Phenylalanin, herangezogen werden. Da die N-Methylierung von Arylidendioxopiperazinen (z. B. 9e) mit Natriumhydrid/Methyljodid ohne Racemisierung moglich ist, sind durch stereoselektive Hydrierung von N-Methylarylidendioxopiperazinen, die L-Prolin enthalten, auch aktive aromatische N-Methylaminosauren zuganglich. Zur Klarung des Zusammenhanges zwischen Struktur und Stereospezifitat wurde auch die katalytische Hydrierung von Alkylidenderivaten des Glycyl-L-prolin-anhydrids wie 13b oder c untersucht, in diesem Falle aber keine asymmetrische Induktion gefunden. Andererseits fuhrte auch eine Wasserstoffanlagerung an l-Acetyl-6-benzyliden-3-isobutyl-2,5-dioxopiperazin, welches gegenuber 9dL-Leucin an Stelle von L-Prolin enthalt, zu racemischem Phenylalanin. On Amino Acids and Peptides, VIII. Asymmetric Induction in the Course of Reactions of Amino Acids and Peptides, I. Asymmetric Synthesis of Aromatic α-Amino Acids and N-Methyl-α-Amino Acids. Synthesis of L-Dopa. On the Catalytic Hydrogenation of Unsaturated Cyclodipeptides Catalytic hydrogenation of arylidene derivatives of glycyl-L-proline anhydride such as 9a–e proceeds with high asymmetric induction. This sequence of reactions followed by acid hydrolysis of the saturated dioxopiperazines may be used for the synthesis of active aromatic amino acids such as L-dopa or L-phenylalanine. Since N-methylation of arylidenedioxopiperazines using sodium hydride/methyl iodide is possible without racemization, active aromatic N-methylamino acids may also be obtained by stereoselective hydrogenation of N-methylarylidenedioxopiperazines which contain L-proline. In order to determine the relationship between structure and stereospecifity, the catalytic hydrogenation of alkylidene derivatives of glycyl-L-proline anhydride such as 13b or c was also investigated. In this case no asymmetric induction was observed. On the other hand, addition of hydrogen to l-acetyl-6-benzyliden-3-isobutyl-2,5-dioxopiperazine, which corresponds to 9d but contains L-leucine in place of L-proline, also led to racemic phenylalanine.

Der Gesteinsabbau durch Ätzmuscheln an Kalkküsten

Abstract: Verteilung und Populationsdichte der Atzmuscheln werden bestimmt durch Wassertiefe und Neigungswinkel der Kuste sowie besonders durch die Art des Substrates. Oolithische Kalke sind 2–3mal starker besiedelt als Dolomit.

How Chaotic is a State of a Quantum System

Abstract: A concept related to the entropy is studied. Let A and B be two density matrices, with eigenvalues a1, a2,… and b1, b2,…, arranged in decreasing order and repeated according to multiplicity. Then A is said to be “more mixed”, or “more chaotic”, than B, if a1⩽b1, a1+a2⩽b1+b2,…,a1+…+am⩽b1+…+bm,…; It turns out that if A is more mixed than B, then the entropy of A is larger than the entropy of B. However, more generally, let v be an arbitrary concave function, ⩾0, and vanishing at 0. Then, if A is more mixed than B, tr v(A)⩾tr v(B). It is shown that also the converse is true. Furthermore, a variety of other characterizations of the relation “A is more mixed than B” is obtained, and several applications to quantum statistical mechanics are given.

A-alpha-nerve-fiber: number of neurotubules in the stem fibre and in the terminal branches.

Abstract: Cross sections of A-α-motor stem fibres of the rat accessory nerve and of one of its branches, the N. musculi sternomastoidei were compared with cross sections of terminal branches of the same nerve, with respect to the axonal cross sectional areas and the number of neurotubules. The absolute number of neurotubules in a stem fibre was found to be on average five times that of one of its terminal branches, corresponding to the ratio of their axonal cross-sectional areas. Thus no significant differences could be found in the tubular density of large stem fibres and of small final branches. Taking into account that in the course of the terminal ramification the total axonal cross-sectional area increases (Zenker and Hohberg, 1973), the combined total of the numbers of neurotubules in all terminal branches of a single A-α-fibre of the nerve innervating the sternomastoid muscle surpasses the amount of tubules in the stem fibre on average about 11 times. These findings are incompatible with the idea of a constant number of neurotubules within a given axon and its branches. In accordance with recent biochemical studies of microtubular protein, our results indicate that neurotubules may be formed in axon branches far from the perikaryon.

Neue K-Boride und verwandte Phasen (Re3B-Typ, aufgefüllt)

Abstract: Mit Hilfe vonWeissenberg-Aufnahmen wird die Kristall-struktur der K(Kappa)-Hf−Mo−B-Phase verfeinert. Die Punktlage 2 a) in P63/mmc ist durch Mo-Atome (nicht Boratome) aufgefullt. Damit entsteht praktisch Strukturgleichheit mit Co2Al5 bzw. Mn3Al10. Die analogen K-Boride Zr9Mo4B (mit Hf9Mo4B luckenlos mischbar) und Zr9W4B bestehen ebenfalls. In Hf9Mo4B werden bis 14 At% Al (1400°C) aufgenommen.

The mechanism of the drinking response to some hypotensive drugs: activation of the renin-angiotensin system by direct or reflex-mediated stimulation of -receptors.

Abstract: The increase in water intake and plasma renin concentration (PRC) in response to the administration of the α-receptor blocker phentolamine (10 mg/kg) were simultaneously diminished or abolished by ganglionic blockade with pempidine (10 mg/kg) or camphidonium (10 mg/kg) as well as by pretreatment with reserpine or 6-OH-dopamine. In contrast, the effects of the β-mimetic agent, isoprenaline (250 μg/kg), on both parameter remained unchanged. The (−)-isomer of propranolol (200 μg/kg) selectively blocked the dipsogenic and PRC-raising effects of isoprenaline and phentolamine, thus demonstrating that a specific β-receptor blockade antagonizes the drinking and increase in PRC induced by the drugs used.