Showing papers by "Humboldt University of Berlin published in 1982"

Experimental Studies on New Liquid Embolization Mixtures (Histoacryl-Lipiodol, Histoacryl-Panthopaque)

Abstract: In vitro measurements have proved that the polymerization time of n-butylcyanoacrylate (Histoacryl) can be delayed markedly and controlled by adding an oily radiopaque material. Our animal experiments have shown that a mixture of Histoacryl and Lipiodol ultrafluid at a 1:3 ratio provided an optimal embolization material with good flow properties, polymerization time of approximately 7 sec and excellent contrast definition. This mixture may be handled easily, with a minimum of risk involved when used with a 40% glucose solution.

Mean spherical approximation-mass action law theory of equilibrium and conductance in ionic solutions

Abstract: An improved Bjerrum theory obtained by combining the mean spherical approximation with the mass action law (MSA&MAL) is used to calculate the fraction of ions unpaired over the full range of states of a primitive model electrolyte It is combined with a new theory for the electrical conductance of the primitive model under the MSA to yield the conductance of an electrolyte over a wide range of concentrations and Bjerrum parameters with only two parameters Ao and R, the distance of closest approach, adjusted to fit the conductivity data The theory fits the data for aqueous alkali halides over a wide concentration range with Ao values in good agreement with those deduced by more conventional theories and with reasonable small ion pairing constants deduced from the data It fits the data for LiBr in octanol without the need for invoking triple ion formation It leads to reasonable predictions for the conductance curves for 1:1 electrolytes even up to the molar region for solvents with dielectric constant from 10 to 80

Stimulation of wound healing, using brain extract with fibroblast growth factor (FGF) activity. I. Quantitative and biochemical studies into formation of granulation tissue.

Abstract: Summary In rats with polyvinyl rings implanted under the dorsal skin, the formation of granulation tissue was found to be stimulated by application of brain extract with fibroblast growth factor (FGF) S3 activity which had been obtained from cattle. This stimulating effect on wound healing proved to depend on doses and was detectable in rats aged two and six months on the third and seventh postoperative days. The desired action could be induced only by repetitive administration of FGF S3 or by coupling of the latter to SYSpur-derm®, a synthetic dermatoplastic material. More fractions with potential agtion upon formation of granulation tissue proved to be obtainable from further biochemical separation of FGF S3. One of such fractions was successfully concentrated to a potentiality by which one tenth of the normal dose hielded the same effect as the full dose. Hexosamine and hydroxyproline levels were measured, at the same time, and found to stimulate fibroblasts. The findings are discussed.

Stimulation of wound healing, using brain extract with fibroblast growth factor (FGF) activity. II. Histological and morphometric examination of cells and capillaries.

Abstract: Summary Reported in this paper are studies by which evidence was produced to increased formation of granulation tissue in rats, aged two and six months, seven days after repeated localised administration of brain extract from cattle with FGF activity (fibroblast growth factor). Such increased formation of granulation tissue was attributable to the formation in the same granulation tissue of larger amounts of capillaries, which actually provided conditions for better blood supply. The above increase was associated with stimulation of the synthetic function of fibroblasts and myofibroblasts in the granulation tissue. Comprehensive morphometric tests, including differential counting, appeared to show that additional effects had to be assumed, in particular on macrophages and lymphocytes. Such increase in angiogenesis seemed to suggest that in the in vivo model studied FGF proved to be, first of all, a factor of angiogenesis rather than a factor of fibroblast growth. The above results, as obtained from rats which differed in age, exhibited a certain variation in response to FGF. This seems to underline the importance of age-dependent examination also in the context of pharmacological studies.

Lipoxygenase mRNA in rabbit reticulocytes. Its isolation, characterization and translational repression.

Abstract: The synthesis of the erythroid lipoxygenase, an enzyme which is of importance for the degradation of mitochondria during the maturation of reticulocytes to erythrocytes, was studied in reticulocytes from bone marrow and in density-separated fractions from peripheral blood of anemic rabbits. Lipoxygenase mRNA was enriched to about 75% by digestion of polysomes with protease K, poly(U)-Sepharose chromatography and repeated sucrose gradient centrifugation. From sucrose gradient centrifugation, electrophoresis and electron microscopy a molecular weight of about 106 was calculated. Synthesis of lipoxygenase is absent in erythroblasts, in very young reticulocytes obtained from bone marrow, of in the lightest fractions of reticulocytes from the peripheral blood. More mature blood reticulocytes show a considerable synthesis of the enzyme. The induction of the synthesis of the lipoxygenase seems to be initiated when reticulocytes have reached the peripheral blood. It is shown that lipoxygenase mRNA is present in reticulocytes as a translationally inactive free cytoplasmic messenger ribonucleoprotein (mRNP) particle. After deproteinization isolated mRNA obtained from masked mRNP codes for authentic lipoxygenase in a cell-free protein-synthesizing system of reticulocytes.

Non-Condon Approximations and the Static Approach in the Theory of Non-Radiative Multiphonon Transitions

Abstract: The off-diagonal matrix element of the non-adiabaticity operator, on which usually the theory of non-radiative multiphonon transitions is based, is recast into a form much more convenient for the calculation of the transition probability W in non-Condon approximation. This is demonstrated first for a two-level system coupled to a single vibrational mode and then extended to the more general case of a complete set of non-degenerate electronic states coupled linearly to N normal modes. The strong anharmonicity of the adiabatic potentials due to the mixture of states caused by the electron–phonon interaction operator is stressed, which limits the applicability of the theory to situations where only transitions well below “level crossing” are important, and, consequently, imposes serious restrictions on the parameters of the system and the temperature. Keeping to these restraints and to two electronic levels, the transformed matrix element of the non-adiabaticity operator is identical with that of the perturbation operator used in the static coupling scheme of Haug and Passler, which turns out in this way to be equivalent to a closed-form of non-Condon approximation based on a well defined set of adiabatic wave functions. Explicit expressions for W are also given, and some aspects of the theory in general are discussed. Das nichtadiabatische Matrixelement des Operators, von dem ublicherweise die Theorie der strahlungslosen Multiphononubergange ausgeht, wird in eine Form uberfuhrt, die den Aufwand fur die Berechnung der Ubergangswahrscheinlichkeit W in Nicht-Condon-Naherung wesentlich reduziert. Dies wird zunachst fur ein Zwei-Niveau-System gezeigt, das an nur eine Schwingungs-mode gekoppelt ist, und dann fur den allgemeinen Fall eines vollstandigen Systems von (nicht-entarteten) Elektronenzustanden bei linearer Kopplung an N Normalmoden erweitert. Die ausgepragte Anharmonizitat der adiabatischen Potentiale infolge der Mischung der Zustande durch den Elektron–Phonon-Wechselwirkungsoperator schrankt die Anwendbarkeit der Theorie auf Situationen ein, in denen nur Ubergange unterhalb der respektiven „Niveauuberschneidungen” von Bedeutung sind, was wiederum Einschrankungen fur die Systemparameter und vor allem die Temperatur zur Folge hat. Bei Einhalten dieser Bedingungen und Beschrankung auf zwei Niveaus ist das transformierte Matrixelement des nichtadiabatischen Operators identisch mit dem des Wechselwirkungsoperators des „statischen Kopplungsschemas” nach Haug und Passler, das sich somit als aquivalent einer geschlossenen Nicht-Condon-Naherung erweist. Es werden Ausdrucke fur W angegeben und einige Aspekte der Theorie der strahlungslosen Ubergange im allgemeinen diskutiert.

Echinocyte formation induced by potential changes of human red blood cells

Abstract: In isotonic 30mm NaCl-saccharose solution, human red blood cells with intact membrane and normal inside ionic content (C-state) indicate a transmembrane potential between +30 mV (at pH 7.4) and +46 mV (at pH 5.1). After treatment with amphotericin B or nystatin as ionophores, a Donnan equilibrium (D-state) will be reached with the same potential at pH 5.1 but a sharp drop down to −20 mV will occur at pH 7.4. Concerning the erythrocyte shape at these states, a stomatocyteechinocyte transformation takes place, in correlation with the potential shift. Stomatocytes formed at ΔΨ>+25 mV, echinocytes at ΔΨ<+25 mV. At potentials lower than +5 mV, no further effect can be observed. This process is reversible. Neuraminidase treatment as well as outside EDTA do not influence this process significantly. Human serum albumin in concentrations of 2% stabilizes the stomatocytes.

Models of Darwinian processes and evolutionary principles

Abstract: Evolutionary processes are described as stochastic motions in a genotype space (set of sequences with a Hamming distance) and a phenotype space (vector space of phenotypic properties). Real value functions are introduced which form a landscape over these spaces; smoothness postulates are formulated. Evolution is considered as a kind of hill climbing on these adaptive landscapes. A rather simple diffusion approximation for the phenotypic processes is proposed which leads to similar mathematical problems as the Schrodinger equation for disordered potential distributions.

Studies on the range of tissue protein synthesis in pigs: the effect of thyroid hormones.

Abstract: The effects of thyroid hormones on the range of tissue protein synthesis in growing pigs using the constant infusion technique with [14C]lysine were studied. 2. During a 6 h infusion, samples were taken from blood and, at the end of the infusion, from liver, pancreas, stomach, small and large intestines, kidney cortex, kidney medulla, muscle and skin. 3. Lower relative specific radioactivities of free leucine and lysine in several tissues were observed in the hormone-treated group than in the untreated one. 4. The range of protein synthesis rate and the daily amount of protein synthesized in tissues was higher in all tissues after application of thyroid hormones. 5. Assuming that the organs analysed represented 70% of the total trichloroacetic acid-precipitable protein of the pig, the estimated range of daily protein synthesis was 251-490 and 312-880 g in untreated and hormone-treated pigs respectively.

Thermodynamic Functions of Nonideal Hydrogen Plasmas

Abstract: The contribution of the charged components to the thermodynamic functions is analysed on the basis of the present theoretical knowledge. In the high-temperature low-density limit the Debye formula with quantum corrections is used. In the low-temperature high-density limit the Gellman-Brueckner formula for the electrons and a lattice-energy formula for the protons is used. Padee-approximants are constructed which contain these limiting situations as special cases and describe also the region between them in certain aproximation. Thermodynamische Funktionen eines nichtidealen Wasserstoffplasmas Auf der Grundlage der derzeit verfugbaren Kenntnisse wird der Beitrag der geladenen Komponenten zu den thermodynamischen Funktionen untersucht. Fur die Hochtemperatur-Niedrigdichte-Grenze wird das Debye-Gesetz mit Quantenkorrekturen benutzt. In der Tieftemperatur-Hochdichte-Grenze werden fur die Elektronen die Theorie von Gell-Mann und Brueckner und fur die Protonen die Gitterenergie ausgenutzt. Es werden Pade-Approximationen konstruiert, welche dieses Grenzverhalten als Spezialfalle enthalten und das Verhalten im Zwischenbereich angenahert wiedergeben.

Lattice Parameter Study in the Bi1–xSbx Solid‐solution System

Abstract: The lattice parameters of Bi1–xSbx single crystals were measured for 0 ≦ x ≦ 1 by a special X-ray diffractometer technique using reflections chosen so that minimum errors were achieved. Corrections for thermal expansion and refraction were applied. The antimony concentration was determined by means of electron microprobe analysis. The dependences of the lattice parameters on x (in nm) can be described with good approximation by a = 0.45469 – 0.02398x and c = 1.186294 – 0.058632 [1 + 1.26 (x−1 – 1)]−1, resp. The behaviour of the parameter a is in agreement with the earlier study by CUCKA and BARRETT, whereas their linear expression for c(x) (0 ≦ x ≦ 0.3) was not confirmed. Die Gitterkonstanten von Bi1–xSbx-Einkristallen wurden fur 0 ≦ x ≦ 1 mit einer speziellen rontgendiffraktiometrischen Methode gemessen. Die Reflexe wurden so ausgewahlt, das sich minimale Fehler der Gitterkonstanten ergaben. Die Werte wurden hinsichtlich thermischer Ausdehnung und Brechung korrigiert. Die Antimonkonzentration wurde mittles Elektronenstrahlmikroanalyse bestimmt. Die x-Abhangigkeit der Gitterkonstanten (in nm) kann mit guter Naherung durch a = 0.45469 – 0.02398x bzw. c = 1.186294 – 0.058632 [1 + 1.26 (x−1 – 1)]−1 beschrieben werden. Das Verhalten der Gitterkonstante a ist in Ubereinstimmung mit einer fruheren Untersuchung von CUCKA und BARRETT, wahrend die von ihnen angegebene lineare Abhangigkeit fur c(x) (0 ≦ x ≦ ≦ 0.3) nicht bestatigt werden konnte.

Carp Insulin: Amino Acid Sequence, Biological Activity and Structural Properties

Abstract: The amino acid sequence of insulin of carp (Cyprinus carpio) has been determined and correlated with its biological activity in a fat-cell test and its structural properties as measured by circular dichroism and sedimentation analysis. The amino acid sequence of carp insulin displays some unusual features: the B chain is longer at the N ter- minus by two residues as compared with mammalian insulins and there are substitutions of the charged residues, found in most insulins at positions B21 and B22, by proline and threonine respectively. On the other hand, all amino acid residues essential for biological activity and for the association of insulin monomers are the same in carp insulin. Accordingly, the half-maximal response in a fat-cell test is reached with carp insulin at concentrations which are only three times higher than with porcine insulin and the maximal response is the same. The circular dichroism spectrum of carp insulin resembles greatly that of bovine insulin indicating that it has a similar spatial structure. Despite amino acid substitutions in the dimer-dimer contact region, carp insulin is able to form hexamers.

Dynamics of non-linear biochemical systems and the evolutionary significance of time hierarchy

Abstract: Several non-linear reaction networks are analyzed in order to study the influence of time hierarchy on the dynamics of biochemical systems. The analysis is based on the assumption that the separation of the time constants within metabolic systems is a direct consequence of strong differences of enzyme concentrations. Therefore, as variable system parameters, only the enzyme concentrations are considered. By investigation of the stationary states of various three-component models with feedback-activation bifurcation diagrams within a two-dimensional parameter space, the enzyme simplex, are constructed. The diagrams contain the information about the number of stationary states, their stability properties as well as the type of motion expected at different parameter combinations. The results support the hypothesis that systems with separated time constants generally show a simple dynamic behaviour. Complex motions can be expected mainly for systems without time hierarchy, which are characterized by parameters located within the centre of the enzyme simplex. Quantitative measures for the time hierarchy and the complexity of the dynamics are derived. It is supposed that the separation of time constants is a main feature of the evolution of biochemical systems. The hypothesis is further supported by the consideration of the time hierarchy of the glycolytic pathway.

Correlated ultrastructural and morphometric studies on the liver during prenatal development of rats

Abstract: Quantitative and qualitative changes in liver tissues during prenatal development were studied by electron microscopy and morphometry. On the 15th day, 30% of fetal liver volume consisted of hepatocytes, and the extrahepatocytic spaces amounted to 63%. The hemopoietic cells occupied 93% of the extrahepatocytic spaces. Immature bile canaliculi were observed and amounted only to 0.14% of extrahepatocytic spaces. The hepatocytes were irregular in shape and possessed several large lipid droplets which amounted to 19% of the cytoplasm. Although the rough surfaced endoplasmic reticulum (RER) was well developed, the smooth surfaced endoplasmic reticulum (SER) was not yet differentiated. The typical peroxisomes with nucleoid and glycogen were not observed in the cytoplasm. On the 18th day the volumetric densities of hepatocytes and bile canaliculi were increased. The typical peroxisomes with nucleoid appeared in the cytoplasm. The accumulation of glycogen which amounted to 12% of the cytoplasmic volume had taken place, while the volume of lipid droplets decreased significantly. In glycogen areas the differentiation of SER began. At birth the histogenesis of the liver was well established. The hemopoietic cells decreased in number and were confined to perisinusoidal spaces. The volumes of biliary capillaries and sinusoids were comparable with these of young rats now. The volumetric density of hepatocytes increased and occupied about 74% of the liver. The volumetric densities of mitochondria, SER, peroxisomes, secondary lysosomes, and lipid droplets increased significantly in comparison with those of the 18 days old fetus, while RER, Golgi area, and primary lysosomes were rather constant. The volumetric density of glycogen decreased rapidly at birth.

Theory of Non‐Radiative Multiphonon Capture Processes. Solution of Old Controversies

Abstract: The solution is given for long persisting controversial problems in the theory of non-radiative multiphonon capture of free carriers. Taking the adiabatic wave functions as basic states for the perturbational treatment of the transition probability particular attention is focused on the correct determination of the transition matrix elements. In this framework it is shown that to first order in the non-diagonal matrix element of the electron-lattice interaction all approaches developed so far (Condon approximation, non-Condon approximation, static approximation, etc.) lead to the same result, in contradiction to statements in the literature. In particular, the reason is found why earlier results for the transition rate within the adiabatic and Condon approximation are much too small. The static approximation is shown to be the lowest approximation to the adiabatic approach. In der vorliegenden Arbeit werden uber mehrere Jahrzehnte andauernde Kontroversen in der Theorie strahlungsloser Vielphononen-Prozesse gelost. Bei der storungstheoretischen Behandlung der Ubergangswahrscheinlichkeit auf der Grundlage adiabatischer Basiszustande wird der korrekten Berechnung der Ubergangsmatrixelemente besondere Aufmerksamkeit gewidmet. Im Gegensatz zu Aussagen in der Literatur wird gezeigt, das alle bisher bekannten Zugange (Condon-Naherung, Nicht-Condonsche Naherung, Statische Naherung usw.) in niedrigster Ordnung bezuglich der nichtdiagonalen Elektron–Gitter-Kopplung zu dem gleichen Resultat fuhren. Insbesondere wird geklart, warum in fruheren Arbeiten im Rahmen der adiabatischen und Condon-Naherung viel zu kleine Werte fur die Ubergangswahrscheinlichkeit erhalten wurden. Die statische Naherung erweist sich als die niedrigste Approximation fur die adiabatische Theorie.

Tumours of the lacrimal gland

Abstract: Up to 7% of orbital tumours are tumours of the lacrimal gland. Their clinical and pathological peculiarities are emphasized. The diagnosis of the type is established by histology only. A biopsy is not advisable. The best treatment is a total excision, which may include orbital exenteration in the case of a malignant mucoepidermoid tumour.

Isoelectronic Impurity Te in CdS1−xSex Mixed Crystals

Abstract: In hexagonal CdS1−xSex amalgamation-type mixed crystals the isoelectronic impurity Te is studied as a function of the composition x in the range 0 ≦ x ≦ 1 by emission and excitation measurements at 4 and 77 K. The binding energies of excitons bound to isolated Te impurities and nearest-neighbour Te pairs are found to decrease strongly with increasing x. For x ⪆ 0.85 isolated Te cannot bind an exciton and, therefore, in CdSe only Te pairs lead to bound impurity states. The measured relaxation energies and halfwidths of the corresponding emission and excitation bands yield information on the x-dependence of the electron-phonon interaction for both types of impurities. The experimental results are discussed on the basis of a simple potential-well model using variational calculations. In hexagonalen CdS1−xSex-Amalgamtyp-Mischkristallen wird die isoelektronische Storstelle Te als Funktion der Zusammensetzung x im Bereich 0 ≦ x ≦ 1 durch Emissions- und Anregungsmessungen bei 4 und 77 K untersucht. Es wird festgestellt, das die Bindungsenergic von Exzitonen an isolierten Te-Storstellen und Te-Paaren in Nachst-Nachbarposition stark mit wachsendem x abnimmt. Fur x ⪆ 0,85 kann eine isolierte Te-Storstelle kein Exziton binden und in CdSe fuhren daher nur Te-Paare zu gebundenen Storstellen-Zustanden. Die gemessenen Relaxationsenergien und Halbwertsbreiten der entsprechenden Emissions- und Anregungsbanden liefern Aussagen uber die x-Abhangigkeit der Elektron-Phonon-Wechselwirkung fur beide Typen von Storstellen. Die experimentellen Ergebnisse werden auf der Grundlage eines einfachen Potentialtopf-Modells unter Benutzung einer Variationsrechnung diskutiert.

Zur Kenntnis der Fruchtmorphologie der Papaveraceae Juss. s. str. und der Hypecoaceae (Prantl et Kündig) Nak

Abstract: Basierend auf vergleichend-morphologischen Untersuchungen an 20 Papaveraceae-Gattungen wird eine Beschreibung der Fruchtmorphologie (incl. Anatomie) fur jede Gattung gegeben. Bei 4 Gattungen konnte lediglich auf Angaben aus der Literatur zuruckgegriffen werden. Fur die 4 Triben sind bestimmte Kombinationen von Differenzierungsmerkmalen charakteristisch. Besondere Beachtung fanden dabei die Struktur der auseren und inneren Perikarp-Epidermis, die Chlorenchym-Verteilung, der Verlauf der Milchrohren, die Gynoeceumsvaskulatur und die Dehiszenzform. Die homokarpellaten Platystemoneae (Unterfamilie Platystemonoideae) sind von den heterokarpellaten Papaveroideae klar abgegrenzt. Die Chelidonieae sind u. a. nach den Dehiszenzformen die plastischste Tribus, hier finden sich zahlreiche ursprungliche Merkmalsauspragungen. Die sich explosiv akropetal offnenden Kapseln der Eschscholzieae sind anatomisch relativ einheitlich. In den Papavereae treten nur unvollstandig basipetal dehiszierende Fruchte auf, die durch fehlende Valvendorsalnerven und im Phloem verlaufende Milchrohren charakterisiert sind. Bestimmte Strukturen weisen auf nahere Bezichungen zwischen Einzelgattungen hin, jedoch rechtfertigt dies keine taxonomische Neugliederung der Familie. Die Hypecoaceae stehen den Chelidonieae (Glaucium, Dicranostigma) und den Eschscholzieae nahe. — Ein phylogenetisches Schema zeigt die karpomorphologischen Beziehungen in den Papaveraceae. Based on comparative morphological capsule studies (incl. anatomy) of 20 papaveraceous genera a description of the fruit structure is given for each genus. 4 genera could be described by literature analysis only. Each tribe is characterized by a defined set of differentiation characters. The following features have been examined in particular: structure of outer and inner pericarp epidermis, localization of chlorenchyma, course of laticifers, vascularization of the gynoceum, and mode of dehiscence. The homocarpellate Platystemoneae (subfam. Platystemonoideae) are clearly separated from the heterocarpellate Papaveroideae. The Chelidonieae are the most plastic tribe concerning dehiscence and other features, they have retained many primitive character states. The capsules of the Eschscholzieae opening violently acropetally are relatively uniform in anatomical respect. In the Papavereae there are incompletely basipetally dehiscing fruits which are characterized by lacking dorsal valve traces and laticifers restricted to the pholem. Special structures indicate closer relations between individual genera but do not demand a new arrangement of the taxa. The Hypecoaceae show comparatively strong affinities to Chelidonieae (Glaucium, Dicranostigma) and Eschscholzieae. — A phylogenetic diagram illustrates the carpomorphological relationships in the Papaveraceae.

A method for solving a class of recursive stochastic equations

Abstract: The existence and uniqueness of solutions of a special type of recursive stochastic equations is investigated. Such equations occur in many stochastic models in which the stochastic process describing the behaviour of the system will be generated by the so-called input.

Elektrosynthese von N‐substituierten DL‐Arylglycinestern und 1,2‐Diarylamino‐1,2‐diarylethanen durch Kathodische Reduktion von Azomethinen in Gegenwart von CO2

Abstract: Electosynthesis of N-Substituted DL-Arylglycineesters and 1,2-Diarylamino-1,2-diarylethanes by Cathodic Reduction of Azomethines in the Presence of Carbon Dioxide The electroreduction of the N-arylidene-arylamines 1–12 in CO2-saturated solvents of low proton availability as DMF at markedly more positive potentials than carbon dioxide end up in carboxylating the C-atom and hydrogenating the nitrogen of the double bond. The resulting N-arylsubstituted DL-arylglycines and traces of carbamates may be isolated as esters, adding ethylchloride during the electrolysis. A competing pathway of the electrocarboxylation is the CC-hydrodimerisation and the hydrogenation of the double bond, whose importance increases with the water content of the solvent. Based on cyclic-voltametric evidence and product analysis the mechanism of the reductive electrocarboxylation reaction is discussed in terms of nucleophilic attack of the azomethine anion radical on a proton or CO2.

Strong‐Field Hopping in Disordered Semiconductors A Problem of Directed Percolation

Abstract: Starting from a density matrix formulation the hopping current induced by phonons and a strong electric field in disordered semiconductors is discussed in dependence on the temperature and the electric field strength. The treatment of the corresponding rate equation makes use of the directed percolation method. Essential informations about the non-ohmic behaviour can be obtained from the analysis of the vertex star. Ausgehend von einer Dichtematrix-Formulierung wird der durch Phononen und ein starkes elektrisches Feld in ungeordneten Halbleitern induzierte Hoppingstrom in seiner Abhangigkeit von der Temperatur und der elektrischen Feldstarke diskutiert. Die Behandlung der entsprechenden Ratengleichung benutzt die Methode der gerichteten Perkolation. Wesentliche Informationen uber das nichtohmsche Verhalten konnen aus der Untersuchung des Vertex-Sterns gewonnen werden.

Automated image analysis of glioblastomas and other gliomas.

Abstract: Tumours of the neuroglia, 172 in all (50 glioblastomas, 65 fibrillar and gemistocytic astrocytomas, 26 pilocytic astrocytomas and 31 oligodendrogliomas), were studied by automated microscopic picture analysis. Thirteen morphometric and densitometric parameters of the tumour cell nuclei as well as two mitotic parameters were determined on 4 μm thick Feulgen slide preparations. The correlation of the results with subjectively established grade of malignancy was examined. A close correlation was found between almost all morphometric-densitometric nuclear parameters and the morphologically established behaviour of the tumours under study. Based on these results both the method of automated microscopic picture analysis and the selected parameters have been assessed as efficient for the evaluation of the behaviour of glial tumours. The results are readily reproducible and can be obtained without requiring much time. An other advantage of this method is the use of histological preparations, which allows a comparison of the overall structure of the tumour as well as a pinpointed examination of those regions that are representative of the tumour. Subjective grading of glial tumours has been greatly objective by automation.

Computerized classification of gliomas by automated microscope picture analysis (AMPA).

Abstract: A karyometric analysis of 346 Feulgenstained biopsy preparations (4 μm) of gliomas (glioblastomas; fibrillar, protoplasmic and gemistocytic astrocytomas; pilocytic astrocytomas; oligodendrogliomas) using the automated microscope picture analysis (AMPA) was carried out in continuation of a previous paper (Martin and Voss 1982). Fifteen morphometrical, densitometrical and mitotic preparation features were evaluated: