Showing papers by "University of Zurich published in 1973"

Chemical mutagen testing on in vivo somatic mammalian cells.

Abstract: Possibilities and limitations in the use of in vivo cytogenetic tests on somatic cells are discussed. Special attention is focused on the problems raised by the relative insensivity of the available procedures. It is emphasized that in planning screening tests the accumulated experience from studies with known chromosome breaking chemicals must be taken into account; theoretical considerations should not override the actual observations. In the Appendix, technical details of the micronucleus test are given. Furthermore, some thoughts are expressed concerning cytogenetic testing on germ cells and embryos.

Cytostatic elimination of syngeneic rat tumor cells in vitro by nonspecifically activated macrophages

Abstract: Syngeneic tumor cell lines induced in inbred DA rats by polyoma virus, dimethylbenzanthracene, or methylcholanthrene were interacted in vitro with syngeneic effector cells. Glycogen-induced peritoneal exudate cells, predominantly polymorphonuclear leukocytes, and proteose peptone-induced peritoneal cells, principally macrophages, were the effector cells employed. Activated, nonimmune macrophages or exudative polymorphonuclear leukocytes produced pronounced morphological changes in syngeneic tumor cells as evidenced by a substantial reduction in tumor cell numbers and appearance of shrunken cells, even though there was no increase in cell debris. Polymorphonuclear leukocytes exerted a generally similar but quantitatively much diminished effect. These effector cells constantly produced a decrease in the incorporation by tumor cells of DNA precursors such as [3H]thymidine and of RNA precursors such as [3H]uridine. In this regard, the effector cells were quite refractory to high doses of X-irradiation. Interaction of target cells with activated, nonimmune macrophages yielded low but consistent signs of cytotoxicity, whereas polymorphonuclear leukocytes gave no such effects. Elimination of functional macrophages by silica, an agent specifically toxic for macrophages, resulted in unrestricted tumor cell proliferation despite continued generation of cytotoxicity. Accordingly, cytostatic mechanisms appear to play a predominant role in the elimination of tumor cells by nonimmune phagocytes. Evidence from a variety of experimental approaches suggest that the cytostatic effect is dependent on cell-to-cell contact.

Robust estimation: A condensed partial survey

Abstract: Prefatory Note This paper was written to stimulate discussion; therefore the pointed style. It was designed to be self-contained and yet to minimize overlap with Huber's (1972) long and basic survey paper, which in particular covers the technical points in more detail. The issues raised are considered basic to reasonable applications of statistics; on the other hand, they suggest and stimulate much novel research in mathematical statistics and probability theory (such as about weak*-continuous functionals serving as robustified maximum likelihood estimators, or about Choquet-capacities describing and replacing sets of probability measures). It is hoped that the paper may help in clarifying some relations between rigorous stochastic models and the world outside of mathematics, and perhaps also in improving understanding and cooperation between pure mathematicians and data analysts. 1. Why Robust Estimation ? What do those "robust estimators" intend? Should we give up our familiar and simple models, such as our beautiful analysis of variance, our powerful regression, or our high-reaching covariance matrices in multivariate statistics? The answer is no; but it may well be advantageous to modify them slightly. In fact, good practical statisticians have done such modifications all along in an informal way; we now only start to have a theory about them. Some likely advantages of such a formalization are a better intuitive insight into these modifications, improved applied methods (even routine methods, for some aspects), and the chance of having pure mathematicians contribute something to the problem. Possible disadvantages may arise along the usual transformations of a theory when it is understood less and less by more and more people. Dogmatists who insisted on the use qf "optimal" or "admissible" procedures as long as mathematical theories contained no other criteria, may now be going to insist on "optimal robust" or "admissible robust" estimation or testing. Those who habitually try to lie with statistics, rather than seek for truth, may claim even more degrees of freedom for their wicked doings. In passing, those who use statistics for sanctification rather than elucidation of uncertain facts (treating it as a replacement rather than aid for thinking) might wonder about the "monolithic, authoritarian structure" (cf. Tukey, 1962) they believe statistics to be. (Furthermore, there are of course tremendous possibilities for publishing under the fashionable flag of robustness, both of very valuable and of less valuable results, keeping needy statisticians from perishing.) Now what are the reasons for using robust procedures? There are mainly two observations which combined give an answer. Often in statistics one is using a parametric model implying a very limited set of probability distributions thought possible, such as the common model of normally distributed errors, or that of

Location of the genes for 5S ribosomal RNA in Xenopus laevis.

Abstract: In situ hybridization of 5S RNA and cRNA transcribed in vitro from Xenopus laevis 5S DNA shows that 5S DNA is localized at or near the telomere region of the long arm of many, if not all, of the X. laevis chromosomes. No 5S DNA is detected near the nucleolus organizer in the normal X. laevis chromosome complement, but in a X. laevis kidney cell line, 5S DNA is found at the distal end of the secondary constriction. The arrangement of 5S DNA in several types of interphase nuclei is described. — During the pairing stages of meiosis the telomeres of most or perhaps all of the chromosomes become closely associated so that the regions containing 5S DNA form a single cluster. This close association might be either a cause or a result of the presence of the similar sequences of 5S DNA on many telomeres. It suggests that the uniformity of 5S sequences on non-homologous chromosomes might be maintained by crossing-over between the chromosomes.

Morphometric model, tissue sampling and test of stereologic procedures

Abstract: SUMMARY Stereologic point counting procedures were applied to estimate volumetric and numerical densities of tissue components residing in and forming a defined, simplified model of human marginal gingiva. This included the quantitative characterization of inflammatory cell infiltrates occurring in the epithelial as well as the connective tissue fractions of this model. The gingival tissue was harvested from defined intraoral sites of 9–15 year-old children and processed under standardized conditions for light and electron microscopic observation. Random cross-sections of this tissue were subjected to morphometric analysis based on a multistage sampling technique. At each sampling level, tests were performed to study (1) the suitability of different test systems, (2) the parameter variation within one and between different biopsies and (3) the comparability and reliability of the data obtained. Based on these tests, a morphometric technique was designed which resulted in an accurate estimation of the various parameters characterizing the model tissue. These parameters were the volumetric densities of the following constituents: oral epithelium, junctional epithelium and its leucocyte content, infiltrated and non-infiltrated connective tissue, and its respective collagen fibre content. Infiltrated and non-infiltrated connective tissue fractions were analysed for their respective volumetric and numerical densities of fibroblasts, neutrophilic granulocytes, monocytes, macrophages, small and medium-sized lymphocytes, immunoblasts, plasma cells and mast cells. Sampling technique, test procedures and the design and results of the morphometric system are discussed.

Die Berechnungskomplexität von elementarsymmetrischen Funktionen und von Interpolationskoeffizienten

Abstract: n(lg2 n?2) multiplications and divisions are necessary to compute the set of elementary symmetric functions inn indeterminates. This lower bound and similar ones for the computational complexity of various evaluation and interpolation problems are obtained by introducing ideas and results from algebraic geometry.

Elektronenspinresonanz freier Radikale bei photochemischen Reaktionen von Ketonen in Lösung

Abstract: Transient alkyl and acyl radicals are detected and identified by electron spin resonance during UV.-Irradiation of dialkyl and alkyl aryl ketones in liquid solutions. They are formed by the primary processes of α-cleavage, intermolecular photoreduction or α-chloro elimination. For several ketones a temperature dependent competition between α-cleavage and photo-reduction is observed indicating a higher energy of activation for the cleavage than for the reduction process. The results are discussed with respect to the photochemical behaviour of the ketones. Electron spin resonance parameters are reported for a variety of radicals. In particular 13C coupling constants support a sigma type structure of acyl radicals and require a nearly planar radical center of t-butyl and isopropyl radicals.

Fusion of Erythrocytes by Sendai Virus Studied by Immuno-Freeze-Etching

Abstract: Extensive fusion of human erythrocytes agglutinated by Sendai virus was observed after 30 s of incubation at 37 C. Electron microscopy of thin sections failed to reveal the presence of virions, viral fragments, or discrete viral antigens reactive with ferritin-labeled antibody at the sites of fusion. Immuno-freezeetching of membrane surfaces demonstrated the dispersal of viral envelope antigens from what appeared to be original sites of viral attachment. Virus-induced clustering of membrane glycoproteins was interpreted as resulting from interaction of viral antigens with membrane receptor proteins and forming the structural basis for fusion of membranes with one another.

Morphogenesis and Ultrastructure of Respiratory Syncytial Virus

Abstract: Respiratory syncytial (RS) virus was grown in Vero cells and fixed for electron microscopy at various stages of maturation. Both filamentous and round or kidney-shaped particles, either with (complete) or without (incomplete) internal structure, were observed. All four morphological forms were identical with respect to their reactivity with ferritin-labeled antibody to RS virus. Freezeetching revealed a structural feature apparently unique for RS virus, namely helical striations around the core on the internal aspect of the envelope. This specific configuration was already detectable during the early stages of viral differentiation of the host cell membrane. Concentration of free virus by zonal ultracentrifugation of culture fluids onto sucrose cushions yielded predominantly filamentous forms up to 10 μm in length.

Fibroblasts as an experimental tool in metabolic and hormone studies. II. Effects of insulin and nonsuppressible insulin-like activity (NSILA-S) on fibroblasts in culture.

Abstract: . .Before cell cultures can be used as a tool for metabolic and endocrine research, standardized conditions for stationary and growing cells must be established. Our results with chicken embryo fibroblasts and with WI-38 human fibroblasts demonstrate that the metabolic behaviour of these cells differs depending on whether they are in a stationary phase (without serum) or in a growing phase (with serum). Energy during growth is derived almost exclusively from glycolysis. Two additional factors determine the rate of glucose consumption and lactate production: The glucose concentration in the medium and the density of the cells, i.e. the number of cells per surface area. Using a pulse of labelled thymidine it can be shown that after a delay fibroblasts simultaneously go through the first S-phase under the stimulatory influence of serum. Stationary cells behave metabolically as contact-inhibited cells with regard to glucose consumption and lactate production. It appeals that serum triggers off a sequence of metabolic events including increased glycolysis, thymidine incorporation into DNA and growth.

The spectral sensitivity of polarized light orientation inCataglyphis bicolor (Formicidae, Hymenoptera)

Abstract: 1. The desert ant,Cataglyphis bicolor, is able to orient towards the pattern of polarized light in the sky even without perceiving information on the sun's position. The accuracy of artificially induced homing courses is not influenced by performing the experiments just before sunrise and after sunset or by shading the sun. 2. However, after destroying the polarization pattern by appropriate filtering of the skylight (Figs. 1 and 2) the azimuth of the sun was found to be sufficient when working as an isolated orientation parameter (Fig. 5). No influence of the sun's altitude could be shown by mirror experiments (Fig. 6b). 3. By artificially shifting the sun's azimuth either during the foraging or during the return run the sun's azimuth competes with the polarization pattern. In that situation the sun has no influence on direction finding (Fig. 6a and b). 4. The ants tested beneath various colour folios working as large sized spectral filters do not show any direction finding capacities as soon as wavelengths shorter than 410 nm are cut off (Fig. 7). This holds irrespective of whether the sun is visible or not. The accuracy of the homing courses is totally restored by means of an edge filter transmitting in the range λ λ 390 nm (Fig. 9). 5. The results strongly support the hypothesis that only the uv.-receptors are involved in polarization analysis.

Evidence for colour vision inDrosophila melanogaster through spontaneous phototactic choice behaviour

Abstract: 1. In aY-tube apparatus, one arm illuminated by a white or monochromatic light of constant intensity, the other by monochromatic lights of various intensities (Fig. 1), the dependence of the spontaneous phototactic choice behaviour ofDrosophila melanogaster, ♀ ♀, on intensity and spectral composition of the stimulus lights and on the state of adaptation has been tested. 2 The slopes of the reaction intensity curves (Figs. 2 and 4) show a significant dependence on the wavelength of the variable light and on the uv content of the constant light as soon as the experimental intensity is high enough to stimulate both receptor systems known in Diptera. 3. The action spectrum at the lowest test intensity (Fig. 3a) reflects the spectral sensitivity of the high sensitivity receptor system of the flies with a peak in the uv near 350 mm and a green peak at 501.5 ± 1,3 nm of the same height. With increasing test intensity (Fig. 3b and c) the green peak shifts to 478.9 ± 1.4 nm and the uv peak increases in relative height to 45 times the green peak height. 4. It can be shown by light adaptation, that the relative height of the uv peak is the result of a central nervous processing wheras the uv sensitivity of the central receptor system is low. The sensitivity maximum of the central system (light adapted state) is situated at 474.6 ± 1.2 nm. 5. The results allow the conclusion on colour vision inDrosophila.

The topographic organization of spinal afferents to the lateral reticular nucleus of the cat.

Abstract: The topographic organization of spinal afferents to the lateral reticular nucleus (LRN) has been reexamined in 34 adult cats. Two modifications of the Nauta technique were used to show secondary terminal degeneration resulting from circumscribed lesions at various levels of the spinal cord. The results demonstrate that the “inner segment” of LRN corresponding roughly to Brodal's magnocellular portion, receives fibers from spinal segments C1–D3, while the “outer segment” corresponding approximately to Brodal's parvocellular protion receives fibers from spinal levels below L3. The “middle segment” — a transitional zone between the two former portions — represents the spinal segments D4–L3. The ascending fibers terminate predominantly on the ipsilateral side; only few degenerated elements are noted within the contralateral nucleus. The subtrigeminal portion does not seem to receive afferent fibers from the spinal cord. This finding raises the question of nomenclature, which is briefly discussed in the light of the classical “nucleus funiculi lateralis” concept. Finally, the present data are consistent with electrophysiological data of Oscarsson, Rosen and collaborators according to which LRN represents spinal levels of convergent inputs from large as well as bilateral receptive fields rather than somatotopically arranged projections from peripheral sense organs.

Extremal plane quasiconformal mappings with given boundary values

Abstract: Publisher Summary This chapter discusses the quasiconformal self mappings f = f x of the unit disc E: |z| x denotes the complex dilatation of the mapping f . By continuation, f induces a homeomorphism of the boundary ∂E onto itself. The chapter presents a proof of Hamilton's theorem for the unit disc, based on the length-area method. The quadratic differentials φ n determined by the extremal quasiconformal mappings of the unit disc with n distinguished boundary points form a maximizing sequence for this integral. The chapter discusses an open problem regarding whether the condition (*) is also sufficient, in other words, whether the converse of Hamilton's theorem is true. The proof presented in the chapter makes use only of the length-area method and well-known properties of quadratic differentials with finite norm.

High-fidelity left ventricular pressure measurements for the assessment of cardiac contractility in man.

Abstract: Left ventricular contractility was assessed in 110 patients by use of Vmax values derived from high-fidelity left ventricular pressure measurements. Instantaneous velocity of shortening of the contractile elements (V CE ) throughout the isovolumic phase of left ventricular systole was calculated by an analog computer using the formula: V CE in muscle lengths (ML)/ sec = ( dP / dt )/28 · P where P represents total left ventricular pressure and dP/dt its first derivative. Vmax was obtained by manual straight line extrapolation of the descending portion of the pressure-velocity curves. Group 1 (control subjects) consisted of 25 patients with no or minimal loading of the left ventricle. Vmax in Group 1 was 1.86 ML/sec. Group 2 consisted of 25 patients with atrial septal defect and Group 3 included 11 patients with slight left ventricular pressure load. In Groups 2 and 3, the Vmax value was not significantly different from that of Group 1. However, in Group 4, which consisted of 23 patients with moderate to severe left ventricular pressure load, Vmax was significantly reduced (1.53 ML/sec); in Group 5, which consisted of 14 patients with coronary artery disease and 6 patients with cardiomyopathy, Vmax was 1.21 ML/sec; and in Group 6, comprising 6 patients with mitral stenosis, Vmax was 1.26 ML/sec. In individual patients in Groups 3 to 5, assessment of contractility by comparison with resting Vmax values was not always satisfactory because of overlap with the range of the control subjects. Isometric exercise by handgrip carried out in 44 patients allowed further differentiation of individual contractile function. In Groups 1 and 2, the response to handgrip was characterized by a significant increase of Vmax with no alterations or changes not exceeding +4 mm Hg of left ventricular end-diastolic pressure. In Groups 3 to 5, we observed normal responses, as well as abnormal reaction to handgrip (increase of Vmax associated with an increase of left ventricular end-diastolic pressure that exceeded 4 mm Hg) and pathologic reaction to handgrip (decrease of Vmax accompanied by an increase of left ventricular end-diastolic pressure). Seven of 13 patients with a normal resting Vmax showed an abnormal or a pathologic reaction. A normal response to handgrip was observed in a few patients with depressed resting Vmax. It is concluded that identification of individual patients with impaired myocardial contractile function requires determination of Vmax both at rest and during an additional stress such as isometric exercise.

Umlagerung von Allyl‐aryläthern und Allyl‐cyclohexadienonen mittels Bortrichlorid

Abstract: Allyl aryl ethers which have no strongly electron attracting substituents undergo a charge-induced [3 s, 3 s] sigmatropic rearrangement in the prescence of 0.7 mole boron trichloride in chlorobenzene at low temperature, to give after hydrolysis the corresponding o-allyl phenols (Tables 1 and 2). The charge induction causes an increase in the reaction rate relative to the thermal Claisen rearrangement of ∼1010. With the exception of allyl 3-methoxyphenyl ether (5), m-substituted allyl aryl ethers show similar behaviour (with respect to the composition of the product mixture) to that observed in the thermal rearrangement (Table 3). The rearrangement of allyl aryl ethers with an alkyl group in the o-position, in the prescence of boron trichloride, yields a mixture of o- and p-allyl phenols, where more p-product is present than in the corresponding product mixture from the thermal rearrangement (Table 4). This ‘para-effect’ is especially noticeable for o-alkylated α-methylallyl aryl ethers (Table 5 ). With boron trichloride, 2,6-dialkylated allyl aryl ethers give reaction products which arise, in each case, from a sequence of an ortho-Claisen rearrangement followed by a [1,2]-, [3,3]- or [3,4]-shift of the allyl moiety (Tables 6 and 7). Ally1 mesityl ether (80), with boron trichloride, gives pure 3-ally1 mesitol (95). From phenol, penta-ally1 phenol (101) can be obtained by a total of five O-allylations followed by three thermal and two boron trichloride-induced rearrangements. The sigmatropic rearrangements of the ethers studied, using D- and 14C-labelled compounds, are collected in scheme 2; only the reaction steps indicated by heavy arrows are of importance. With protic acids, there is a [3,3]-shift of the allyl group in 6-allyl-2,6-disubstituted cyclohexa-2,4-dien-l-ones, while with boron trichloride the [3,3]-reaction is also observed along with the much less important [1,2]- and [3,4]-transformations (Table 8). 4-Allyl-4-alkyl-cyclohexa-2,5-dien-1-ones give only [3,3]-rearrangements with boron trichloride (Table 9). As expected, the naphthalenone 112, which is formed by allowing boron trichloridc to react for a short time with allyl (1-methyl-2-naphthyl) ether (111), undergoes only a [3,4] rearrangement (Scheme 3). Representations of how, in our opinion, the complex behaviour of allyl aryl ethers and allyl cyclohexadienones under the influence of boron trichloride, can be rationalized are collected together in Schemes 4 and 5. In the last part of the discussion section, the steric factors leading to the appearance of the ‘para-effect’, are dealt with (Scheme 6).

13C and 1H NMR spectroscopic studies on the structure of N-methyl-3-pyridone and 3-hydroxypyridine†

Abstract: Carbon and proton NMR spectra of 3-hydroxypyridine and its O-methyl and N-methyl derivatives have been analysed, and are compared with the spectra of the corresponding 2- and 4-substituted pyridines. It is shown, that contrary to quantum chemical predictions and in agreement with chemical experience, 3-hydroxy-pyridine has a phenolic structure in solution. For the N-methyl derivative, however, carbon and proton NMR data clearly demonstrate that this compound should be formulated as N-methyl-3-pyridone. The general problem of the 3-pyridones is discussed on the basis of calculated π-electron densities, IR and NMR data.

Absolute Konfiguration der enantiomeren α-CyclogeraniumsäUren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-und ϵ-Carotine

Abstract: By chemical correlation with manool and ambrein the absolute configurations of the enantiomeric α-cyclogeranic acids, α-cyclogeranials, α-ionones and α- and ϵ-carotenes have been elucidated.

Geltungsbereich und Mechamismus der durch Silberionen katalysierten Propargylester‐Allenylester‐Umlagerung nach Saucy und Marbet

Abstract: The mechanism of the catalysis of the reversible (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) by silver(I) ions was investigated, using optically active and diastereoisomeric esters as well as 14C- and 18O-labelling. In order to work with crystalline materials, mainly p-nitrobenzoates (10, 11: R4 = pO2NC6H4) were used. In some cases the rearrangement 10 ⇄ 11 was studied using acetates (R4 = CH3). The alkyl substituents R1, R2, R3, were widely varied (cf. Tables 1, 2). The solvents in which the rearrangements were performed were in most cases dry chlorobenzene and 96% aqueous dioxane. Silver tetrafluoroborate, the benzene complex of the latter, and silver trifluoroacetate (in chlorobenzene) as well as silver nitrate (in aqueous dioxane) served as catalysts. The amounts of the silver catalysts used varied between 0,5 and 10 mol-%; reaction temperatures applied were in the range 35–95°, The results obtained are as follows: 1 The rate-determining step of the (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) occurs in a silver(I) complex with the substrates (10, 11), which is formed in a pre-equilibrium. This follows from kinetic experiments (cf. Fig. 6, 7, 8, 10) and the fact that the rate of rearrangement (of 10a) is strongly decreased when cyclohexene is added (cf. Fig. 9). In solvents which are known to form complexes with silver(I) ions the rate of rearrangement (of 10a)is much slower than in solvents with similar dielectric constants but with small capacity for complex formation with silver(I) ions (cf. Table 4). Taking into account what is known about silver(I)-alkene and -alkyne complexes (cf. [18]), it is obvious that the (propargyl ester)/(allenyl ester) rearrangement occurs in a π-complex of the silver(I) ion with the triple bond in the propargyl ester or one of the two C,C double bonds in the allenyl ester, respectively. 2 The shift of the carboxyl moiety in the reversible rearrangement 10 ⇄ 11 occurs intramolecularly. p-Nitrobenzoic acid-[carboxyl-14C] is not incorporated during the rearrangement, neither in the reactant 10 nor in the product 11 and vice versa. A crossing experiment gave no mixed products (cf. Scheme 2, p. 882). 3 An internal ion pair can be excluded for the rearrangement 10 ⇄ 11 because the 18O-carbonyl label in the reactant is found exclusively in the alkoxy part of the product (cf. Scheme 3, p. 886, and Table 9). Thus, the rearrangement 10 ⇄ 11 occurs with inversion of the carboxyl moiety. 4 The rearrangement of optically active propargyl esters (10g, 10i) leads to completely racemic allenyl esters (11g, 11i). However, rearrangement of erythro- and threo-10j-[carbonyl-18O] (Scheme 3) shows that the stereospecifically formed allenyl esters erythro- and threo-11j-[18O]-epimerize rapidly in the presence of silver(I) ions. This epimerization is twice and forty times, respectively, as fast as the rearrangement of the corresponding propargyl esters (cf. Fig. 1–5). During epimerization or racemization the 18O-label is not randomized (cf. also Scheme 4, p. 898). 5 The equilibrium of the rearrangement 10 ⇄ 11 depends on the bulkiness of the substituents R1, R2, R3 and of the carboxyl moiety (cf. Table 2). Taking into account these facts (points 1–5), the reversible (propargyl ester)/(allenyl ester) rearrangement promoted by silver(I) ions can be described as a [3s, 3s]-sigmatropic reaction occurring in a silver(I)-π-complex with the C,C triple bond in 10 and a C,C double bond in 11. It is suggested that complex formation in 10 and 11 occurs with the π-bond which is not involved in the quasicyclic (containing six orbitals and six electrons) transition state of the rearrangement (Fig. 11). Thus, the rearrangement is of a type which has recently been called a charge-induced sigmatropic reaction (cf. [26]). Therefore, in our case, the catalysis by silver(I) ions is of a different type from that of transformations of strained cyclic molecules promoted by silver(I) ions (cf. [14] [16] [27]–[31]). Side reactions. Whereas the rearrangement of propargyl esters 10 in presence of silver tetra- fluoroborate in chlorobenzene or silver nitrate in aqueous dioxane leads to the corresponding allenyl esters 11, the rearrangement of 10 with silver trifluoroacetate, especially in the presence of trifluoroacetic acid, results in the formation of the dienol esters 12 and 13, which clearly are derived from 11 (see Scheme 1, p. 881). As shown by the rearrangement of 11 in the presence of p-nitrobenzoic acid-[carboxyl-14C], 12 and 13 arise in part from a not isolated di-p-nitrobenzoate (cf. Scheme 6, p. 905), since radioactivity is found in 12 and 13.

The Nature of Tendon Damage and its Repair

Abstract: UMMARY The various forms of tendon damage are reviewed and characterized. Importance is placed upon differential diagnosis as it determines the therapeutic regimen to be employed in any given case. The technique of tendon transplantation as a relatively new form of treatment is described in detail. RESUME Les divers types de lesions tendineuses sont passes en revue et caracterises. On insiste sur le diagnostic differentiel puisqu'il en resulte une attitude therapeutique particuliere a chaque cas. La technique des transplants tendineux est decrite en detail. ZUSAMMENFASSUNG Die verschiedenen Formen der Sehnenschaden werden besprochen und charakterisiert. Es wird viel Gewicht auf die Differentialdiagnose gelegt, weil diese die Therapie in jedem Fall bestimmt. Die Technik der Sehnen-Transplantation als verhaltnismassig neue Art der Behandlung wird detailliert beschrieben.

Quantitative Determination and Location of Newly Synthesized Virus-Specific Ribonucleic Acid in Chicken Cells Infected with Rous Sarcoma Virus

Abstract: A sensitive and quantitative nucleic acid hybridization assay for the detection of radioactively labeled avian tumor virus-specific RNA in infected chicken cells has been developed. In our experiments we made use of the fact that DNA synthesized by virions of avian myeloblastosis virus in the presence of actinomycin D (AMV DNA) is complementary to at least 35% of the sequences of 70S RNA from the Schmidt-Ruppin strain (SRV) of Rous sarcoma virus. Annealing of radioactive RNA (either SRV RNA or RNA extensively purified from SRV-infected chicken cells) with AMV DNA followed by ribonuclease digestion and Sephadex chromatography yielded products which were characterized as avian tumor virus-specific RNA-DNA hybrids by hybridization competition with unlabeled 70S AMV RNA, equilibrium density-gradient centrifugation in Cs(2)SO(4) gradients, and by analysis of their ribonucleotide composition. The amount of viral RNA synthesized during pulse labeling with (3)H-uridine could be quantitated by the addition of an internal standard consisting of (32)P-labeled SRV RNA prior to purification and hybridization. This quantitative assay was used to determine that, in SRV-infected chicken cells labeled for increasing lengths of time with (3)H-uridine, labeled viral RNA appeared first in a nuclear fraction, then in a cytoplasmic fraction, and still later in mature virions. This observation is consistent with the hypothesis that RNA tumor virus RNA is synthesized in the nucleus of infected cells.