Showing papers by "Charles University in Prague published in 1970"

Biotransformation of Ethyl Benzene, Styrene, and Alpha-Methyl sty rene in Man

Abstract: In eight-hour inhalation experiments with volunteers in a gas chamber, the biotransformation of ethyl benzene, styrene, and α-methylstyrene was investigated. About two-thirds of the vapors are retained in the respiratory tract. After the inhalation was terminated, only traces were found in the expired air in the case of ethyl benzene, but no exhaled styrene could be detected. The amounts of these hydrocarbons excreted in urine were negligible. The main urine metabolite of ethyl benzene and styrene in man is mandelic acid; a smaller portion is eliminated as phenylglyoxylic acid and, in the case of ethyl benzene, as methylphenylcarbinol. Mandelic acid is excreted rapidly from the organism; its determination in urine may be recommended as an index of exposure for ethyl benzene as well as for styrene. In urine of subjects exposed to a-methylstyrene, atrolactic acid was found.

Excitation of triboluminescence by deformation of single crystals

Abstract: The excitation of triboluminescence by elastic and plastic deformation and by fracture of single crystals has been studied in detail by means of a high sensitive experimental apparatus. Typical results are reported for crystals of ZnS(Mn), NaCl(Mn), X-ray-irradiated KI and KCl, and sugar. The experiments show that the characteristic light peaks of triboluminescence are intimately related to the treads occurring in the stress–strain curves. A detailed analysis of these curves in different materials suggests two excitation mechanisms for triboluminescence: 1. excitation by impact of moving dislocations with trapped electrons; 2. excitation by unpinning of dislocations from luminescent centres.

The structure and electronic properties of semiconducting glasses based on CdAs2

Abstract: A new group of amorphous substances based on CdAs 2 has been studied. Glasses are produced if elements of Ge, Si, Mg, Ga, In, Tl and Sb are added to the CdAs 2 melt. A special property of these glasses is that at a temperature of 360 to 410°C they recrystallize. From an analysis of the curves of radial distribution of the atom density we deduce that the basic unit of the structure of such glasses is the tetrahedron CdAs 4 . A mechanism has been proposed for the formation of such glasses and some of its features have been verified by measuring the magnetic susceptibility. Measurements of the shape of the absorption edge and the electrical conductivity show that such glasses have a semiconducting character. The shape of the absorption edge and the dependence on temperature indicate that Urbach's rule holds. The electrical conductivity follows the relation σ = σ 0 exp ( − ΔE /2 kT ); usually it is very low in most glasses and at room temperature is of the order of 10 −6 to 10 −7 (Ω cm) −1 . The activation energy ΔE ≅1 eV does not change very much with the composition of the glass. Exceptions are antimony and thallium glasses, the latter in particular having a relatively high electrical conductivity and ΔE depending strongly on the Tl content. A switching effect was observed in amorphous stoichiometric CdGeAs 2 .

Effect of androgens on histochemical fibre type. Differentiation in the temporal muscle of the guinea pig.

Abstract: The temporal muscles of the guinea pig show a sexual differentiation reflected in their histochemical enzyme pattern. Using histochemical methods for mitochondrial (SDH, α-GPDH), and glycolytic enzymes (phosphorylase, LDH) it could be shown, that in adult animals the “male” muscle is a “white” muscle with marked activity of glycolytic enzymes, the “female” muscle a “red” muscle displaying high activity of mitochondrial enzymes. This differential enzyme pattern can be converted by the application of testosterone to the female type during the postnatal development. The male sex hormone thus affects the histochemical enzyme pattern of the muscle, converting the “red”, “female” into a “white”, “male” muscle in the female guinea pig.

Asymptotic distribution of simple linear rank statistics for testing symmetry

Abstract: The object of the present paper is to derive asymptotic distributions of simple linear rank statistics used for testing symmetry under various systems of conditions. The main result is stated in Theorem 3 (Section 2) and in Theorem 6 (Section 3). The assertions have been derived by the method worked out in [1]. Similar assertions concerning the multivariate case (the other part of the author's thesis) will be published in a next paper.

The Use of Reticulocytes with High Non‐haem Iron Pool for Studies of Regulation of Haem Synthesis*

Abstract: Summary One-hour incubation of reticulocytes with 10−2m isonicotinic acid hydrazide (INH) and transferrin-bound 59Fe changes the normal distribution of radioiron inside the cell. About 10% of 59Fe is found in haem and 90% is present in the non-haem iron pool. The accumulated non-haem radioiron may be utilized for haem synthesis. This is demonstrated by the reincubation of washed reticulocytes with a high non-haem radioiron pool induced by INH under optimal conditions. The incorporation of radioiron from intracellular non-haem pool into haem is used as a method for the estimation of the rate of haem synthesis in the presence of various inhibitors. INH reduces haem synthesis from non-haem iron to a greater extent than that from transferrin iron. On the other hand, haemin, which inhibits the incorporation of 59Fe from transferrin into haem, does not significantly decrease the utilization of intracellular non-haem iron for haem synthesis. These results are considered as further evidence for the inhibitory effect of haem on the membrane transport of iron. Cells with an artificially increased non-haem iron pool incorporate more [2-14C]glycine into haem than normal reticulocytes. These results are in accordance with the possibility that the supply of iron to the critical sites of haem synthesis may be a limiting factor controlling the rate of haem synthesis.

Differentiation of myoblasts and the relationship between somites and the wing bud of the chick embryo.

Abstract: Electron microscope studies were performed of the differentiation of myoblasts in the brachial somites and in the wing bud of chick embryos at stages 17 to 27 according to Hamburger and Hamilton Concurrent optical inspection of short series of stained thick sections enabled the following statement concerning the relationship between the dermomyotome and the wing bud as well as the ingrowing nerve fibers

Three-dimensional reconstructions of astroglia and oligodendroglia cells

Abstract: Three-dimensional reconstructions of portions of astrocyte and oligodendrocyte bodies and processes are presented. The reconstructions have been made from series of ultrathin sections, and have been compared with glial cells in Golgi-impregnation preparations.

The development of teacher education

Abstract: Even those who tend to see the present merely as the product of past thought and action are convinced that in the educational process we face new conditions and new tasks, the solutions of which are not mere modifications of traditional approaches. Attempts to identify the new social and educational situation have already had an international, multidisciplinary impact. Out of the great number of concepts, the classification and evaluation of which are a continuing task for the educationalists, the author has chosen two related ideas which have gradually gained acceptance in international pedagogical discussion.

Application of inert radioactive gases in the study of solids

Abstract: The behaviour of different iron salts (FeSO4.7 H2O, FeC2O4.2 H2O, Mohr's salt, and basic iron carbonate) was studied by means of the emanation method, DTA and dilatometry. The salts were heated within the temperature range of 20 to 1100‡ C, under identical conditions. The results obtained are compared and the process of thermal decomposition of the different salts is discussed. The “activity” of ferric oxide obtained by decomposition of various iron salts is estimated, and it is suggested that the low “activity” of the sulphate-derived ferric oxides is related to a low thermal annealing rate, while the higher “activities” of the other two resultant ferric oxides are similarly related to higher thermal annealing rates.

The effect of aminophylline on the respiration and pulmonary circulation.

Abstract: 1. We have examined the effects of aminophylline on the respiration and pulmonary circulation of eleven patients with chronic bronchitis and six patients with peripheral bronchial carcinoma; the latter were free from bronchial obstruction at the time of study. 2. Aminophylline caused an increase in total and alveolar ventilation and a decrease in arterial carbon dioxide tension. Lung diffusing capacity was unaltered in subjects with marked respiratory insufficiency but increased slightly in an additional group of less severely affected patients, and in the control subjects. 3. Mean pulmonary arterial pressure decreased significantly in the patients with chronic bronchitis but not those with lung cancer. A positive correlation was observed between the level of pulmonary arterial pressure during the control period and the decrease after aminophylline. 4. For the group as a whole there was no significant change in cardiac output or arterial oxygen saturation or tension. However, in those subjects in whom the cardiac output was increased, the arterial blood oxygen was reduced despite an increase in alveolar ventilation. The data are interpreted as evidence for a disproportionate part of the increase in cardiac output being directed to poorly ventilated areas of the lung.

The effect of light intensity on stomatal frequency in leaves of Iris hollandica hort., var. wedgwood

Abstract: Stomatal frequency in leaves of plants of Iris hollandica, cultivated under four light intensities, about 12%, 37%, 75% and 100% of natural daylight, was studied. The stomatal frequency decreases with lower light intensities. The gradients of stomatal frequency of successive leaves show an increase up to the third or fourth leaf with a subsequent decrease of values up to the highest leaf. The total number of stomata per leaf is not constant; differences exist in successive leaves of a shoot as well as among the leaves of plants growing under various light intensities. The character of gradients was changed at lower light intensities. The largest reaction to the light intensity appeared in leaves with higher stomatal frequency. The gradients in individual leaves depend on the insertion of the leaf. Both the shape and the slope of these gradients are influenced by the light intensity.

Asymptotic properties of rank tests under discrete distributions

Abstract: This paper is devoted to problems of rank tests when samples are drawn from purely discrete distributions. There are considered two ways of treatment of ties, and the distribution of the respective test statistics is derived under the hypothesis of randomness and under the contiguous alternative. Furthermore, their asymptotic power and efficiency are established.

Familial occurrence of 18q.

Abstract: An unusual segregation of the partial long arm deletion of a chromosome 18 is reported. This aberration was found in the feeble-minded mother and in her 4 daughters. The fifth child has XXY-Klinefelter's syndrome. The carriers of 18q — in this family reveal small stature, microcephaly, and mental deficiency in the range from feeble-minded to severe imbecility. Other characteristic features commonly found in patients with 18q — syndrome, as mid-face retraction, downward slanting mouth, heart defect, and atretic ear canals were not observed.

Reurbanisation in Postsocialist Europe – A Comparative View of Eastern Germany, Poland, and the Czech Republic

Abstract: Since the 1990s, reurbanisation has become an increasingly frequent trajectory for urban development. Many formerly shrinking cities have been able to stabilise their population or even see new growth. Especially prominent in regions like Germany and the UK, but also observed across the whole continent, a lively debate on reurbanisation has developed as a reality of today’s, and a potential trajectory for tomorrow’s, cities in Europe. Postsocialist Europe has not so far been central in the reurbanisation debate, either empirically or theoretically. Subsequently, the postsocialist experience is missing in the discourse and the existing body of evidence. There is, however, some evidence that Czech and Polish cities are also seeing signs of new inner-city growth and a trend towards core city stabilisation. Against this background, the paper scrutinises the issues of reurbanisation and new growth after the shrinking of postsocialist cities. The paper uses the approach of a contrastive comparison between cities in eastern Germany, where reurbanisation has developed as the predominant trajectory for many large cities, and for cities in Poland and the Czech Republic, where this trend is considerably less prominent. It analyses the development of reurbanisation in these cities and their urban regions over the last few decades, its characteristics and the determinants triggering or impeding it. The paper includes data on a national scale as well as from relevant case studies of cities and their urban regions. It argues, among other things, that there is no “postsocialist model” with regard to influencing factors for reurbanisation. Eastern Germany, due to its specific postsocialist situation and transformation trajectory, can be viewed as an “outlier” or “hybrid” which exhibits characteristics typical of postsocialist and western welfare contexts and which is seeing especially dynamic reurbanisation after a phase of extreme shrinkage. Although there are clear signs of inner-city reurbanisation in Polish and Czech cities as well, it seems relatively unlikely that this process will reach the same high levels as in East German cities within the coming years. * This article belongs to a special issue on reurbanisation.

Partial derivatives of dispersion curves of love waves in a single-layered medium

Abstract: Es werden die ersten und zweiten partiellen Ableitungen der Dispersionskurven von Love-Wellen im Einschichtenmilieu studiert. Die Berechnung der partiellen Ableitungen fuhrt man nicht anhand numerischen Ableitens durch, sondern mit einer schnelleren und genaueren, auf dem Satz der impliziten Funktionen gegrundeten Methode. Die sich aus dem Studium partieller Ableitungen fur die Interpretation der beobachteten Dispersionskurven ergebenden Folgerungen werden diskutiert.

Changes of the Latent Period of Explanted Tissues During Ontogenesis

Abstract: During the first fifty years of work with animal tissues and cells cultured in vitro, it has been clearly shown that the age of the donor determines the behavior of the explants. There are two basic phenomena which have been subjected to detailed experimental analysis. The first of these to be studied was the latent period, defined as the time after which cells first emigrate out of a freshly explanted tissue fragment. This period of dormancy increases with the increasing age of a normal tissue donor. The other phenomenon, which has been known for about 10 years, is the limited lifetime of diploid cells in culture. This lifespan is longer for cells cultured from embryos than for cells cultured from mature donors. Both phenomena have been studied in our laboratory. This paper deals with our findings concerning the relationship between the latent period of fragment cultures from different rat organs and age.

Symmetrical hypogenesis of the cerebellum

Abstract: 28 children were observed with a fairly uniform picture: moderate, bilateral cerebellar syndrome a,mbulatory, generally with support, and, in the EEG, bioccipital, slow, irregular waves, blocked by eye-opening. Air encephalography was performed in 19 cases and always revealed a symmetrical hypoplasia of cerebellum. It is suggested that this is an independent syndrome, not just an ataxic form of cerebral palsy, and because the aetiology seems in the majority of cases to be prenatal, it could be called “symmetrical cerebellar hypogenesis”.