Showing papers by "University of Geneva published in 1974"
TL;DR: This paper studied the interplay between the child's action sequences and his implicit theories which the observer infers from the sequences rather than from his verbal comments, focusing on the role of counterexamples and on shifts in attention from goal to means.
609 citations
TL;DR: B and T blasts from MLN and TDL have, in contrast to blasts from the peripheral lymph nodes, a marked tendancy to home in the gut, and migrate as well in a graft of fetal intestine as in the recipient's own gut, indicating that this selective accumulation is not the result of a mechanism recognizing antigen absorbed from the gut lumen.
Abstract: The nature of the lymphoid cells and blasts (i.e. cells labeled in vitro with [3H]-thymidine) of the Peyer's patches (PP), mesenteric lymph nodes (MLN) and thoracic duct lymph (TDL) has been studied by combined immunofluorescence and radioautography, using antisera directed against T (MSLA) or B (MBLA) cell antigenic determinants, or against various Ig chains. The migration pattern of these various cell populations after transfer to syngeneic mice or rats was determined by radioactivity counting and radioautography and the nature of the homed cells was studied by combined immunofluorescence and radioautography. B and T blasts from MLN and TDL have, in contrast to blasts from the peripheral lymph nodes, a marked tendancy to home in the gut, and migrate as well in a graft of fetal intestine as in the recipient's own gut, indicating that this selective accumulation is not the result of a mechanism recognizing antigen absorbed from the gut lumen.
The gut-homing B blasts are cells bearing surface IgA (sIgA) and containing intracellular IgA, which transform into IgA plasam cells in the lamina propria. Evidence is discussed that the progenitors of the intestinal IgA plasma cells are proliferating sIgA cells from the PP geerminal centers, which migrate via lymphatics to MLN and TDL and mature during this migration, acquiring intracellular IgA chains as well as a gut-homing mechanism which might be related to this increased IgA synthesis.
The gut-homing T blasts migrate both in the lamina propria and the intestinal epithelium. Most, if not all, the intraepithelial lymphocytes of the gut mucosa appear to be T lymphocytes derived from rapidly dividing cells. Evidence is presented for the existence in the lymphoid system of two types of T blasts, one that is circulating and has a marked tendancy to home to the gut, and a second that does not home to the gut and may be sessile.
367 citations
TL;DR: The findings, demonstrating a contractile system other than bronchial and arterial smooth muscle, suggest that the alveolus should no more be conceived as a passive "organ."
Abstract: In the lungs of healthy rats, humans, lambs, and monkeys, about 50% of the alveolar interstitial cells—resembling fibroblasts—contain bundles of fibrils measuring 30–80 A in diameter. Immunofluorescence studies on frozen sections of rat lung demonstrate that many interstitial cells bind sera containing antiactin antibodies. On account of these two sets of findings and our additional in vitro studies suggesting alveolar tissue contraction due to hypoxia or epinephrine, we postulate that the alveolar septa contain contractile cells different from that of smooth muscle. For these cells we propose the name of "contractile interstitial cells." Such cells lie within the thick portion of the air-blood barrier and around the pre- or postcapillary vessels. Hence it is possible that they play a role in the autoregulation of ventilation/perfusion (V/Q) ratio, particularly in hypoxic pulmonary hypertension. These findings, demonstrating a contractile system other than bronchial and arterial smooth muscle, suggest that the alveolus should no more be conceived as a passive "organ."
334 citations
TL;DR: This paper proves a theorem (“Theorem 6”) on the composition of the Butcher series, shown to be fundamental for the theory of Runge-Kutta methods, and extends the multi-value methods of J. Butcher to the multiderivative case, which leads to a big class of integration methods for ordinary differential equations, including the methods of Nordsieck and Gear.
Abstract: This paper proves a theorem (“Theorem 6”) on the composition of, what we call, Butcher series. This Theorem is shown to be fundamental for the theory of Runge-Kutta methods: the formulas for the Taylor expansion of RK-methods and multiderivative RK-methods as well as formulas for the operation of the “Butcher group” (which describes the composition of RK-methods) are easy consequences. We do not attempt to realize the series as (generalized) Runge-Kutta methods, so we are not forced to restrict ourselves to the finite dimensional case. The theory extends to the multiderivative case as well, and the formulas remain valid for series which are not realizable as Runge-Kutta methods at all. Finally we extend the multi-value methods of J. Butcher [2] to the multiderivative case, which leads to a big class of integration methods for ordinary differential equations, including the methods of Nordsieck and Gear [3]. The defintions and notations of [4] are used throughout this paper, many of the results are proved here again.
209 citations
TL;DR: It is suggested that in infections defective in late gene expression and consequently in the maturation of replicated DNA, the increased P32 production is caused by the large expansion of the DNA pool.
111 citations
TL;DR: For example, this article showed that the structure of the insulin-producing B-cells and their functional activity was not limited to the determination, by light microscopy, of the degree of cytoplasmic granularity using specific stains such as that described by Gomori.
Abstract: Before 1950, correlation between the structure of the insulin-producing B-cells and their functional activity was essentially limited to the determination, by light microscopy, of the degree of cytoplasmic granularity (Fig. 1) using specific stains such as that described by Gomori [14]. The advent of electron microscopy opened a whole new stratum of biological organization, stretching from about 2.000 A -the limit of resolution of the light microscope -down to 50 A, and later 20 A, for most biological specimens. The first explorers of these new territories drastically extended our knowledge of the organization of cells, and created an atmosphere of great excitement for morphological sciences. The result was a growing appreciation of the fact that there is a physiological, as well as a biochemical meaning in the minute-scale organization of cells. This organization turned out to be much more elaborate than previously assumed, and many intraeellular membranebounded compartments could be described.
104 citations
TL;DR: In this article, proteins from the 30 S ribosomal subunit of Escherichia coli were fractionated by column chromatography and individually incubated with 16 S RNA, and each of the RNA fragments was characterized by fingerprinting and positioned within the sequence of the 1600-nucleotide 16S RNA molecule.
103 citations
TL;DR: The results parallel those obtained in various mammalian and avian species and suggest that the homology of the major histocompatibility complex (MHC), described in higher vertebrates, can be extended to amphibians.
Abstract: The genetic relationship between mixed leukocyte reaction (MLR), skin graft rejection, and some red blood cell antigens has been studied in a sibship of the toadXenopus laevis. MLR typing was achieved using blood lymphocytes. The graft experiments were performed at 17–19°C. Grafts exchanged between MLR identical sibs were rejected in 30.9±5.1 days, grafts exchanged between MLR different sibs were rejected in 20.4±2.4 days when animals differed at one MLR haplotype, and in 18.6±1.9 days when they differed at two MLR haplotypes. Immunizations and absorptions following the MLR typing produced agglutinating antisera that recognize red blood cell antigens segregating with MLR haplotypes. The results parallel those obtained in various mammalian and avian species and suggest that the homology of the major histocompatibility complex (MHC), described in higher vertebrates, can be extended to amphibians.
89 citations
TL;DR: It would appear that the conditions of denaturation used do not equally denature parainfluenza virus RNA and other RNAs, such as cellular rRNA, 45S rRNA precursor, and R17 RNA.
Abstract: The molecular weights of Sendai and Newcastle disease virus RNA were estimated by sedimentation in sucrose gradients and by length measurements in the electron microscope under both denaturing and nondenaturing conditions. Sedimentation analyses under denaturing conditions yielded molecular weight estimates of 2.3 x 10(6) to 2.6 x 10(6), whereas length measurements yielded estimates of 5.2 x 10(6) to 5.6 x 10(6) for both denatured and nondenatured viral RNA. It would appear that the conditions of denaturation used (99% dimethyl sulfoxide at 26 C, and reaction with 1.1 M formaldehyde for 10 min at 60 C) do not equally denature parainfluenza virus RNA and other RNAs, such as cellular rRNA, 45S rRNA precursor, and R17 RNA.
81 citations
TL;DR: The results of 63 new radiometric K-Ar and Rb-Sr measurements on metamorphic minerals from the internal units of the Western Alps show Hercynian, Permian, as well as three Alpine age groups.
Abstract: The results of 63 new radiometric K-Ar and Rb-Sr measurements on metamorphic minerals from the internal units of the Western Alps show Hercynian, Permian, as well as three Alpine age groups. The first of the Alpine ages cover the period between 78 and 100 m.y. and refer to high pressure parageneses. The second group comprises K-Ar 39 to 50 m.y. ages; these values are affected by some inherited argon, as indicated by Rb-Sr measurements which point to 35–36±4–5 m.y., i.e. similar to the culmination of the Lepontine crystallization. The final group includes 15 to 30 m.y. ages. It is not yet clear which geologic processes have led to this isotope re-equilibration. Large amounts of inherited argon have been found in Alpine metamorphic minerals of the basement rocks.
81 citations
TL;DR: A mutation which maps between genes 52 and t defines a new regulatory gene in IN T4 infections, and some of the properties of such a mutation are described.
Abstract: IN T4 infections the mechanisms determining the time and rates of expression of early genes are not yet clearly understood. Although mutants which do not make late gene products or which are defective in DNA synthesis generally fail to turn off the synthesis of most early gene products, no mutations have been described which affect either the time of appearance or the initial rate of synthesis of proteins from more than a single early gene. This preliminary report describes the isolation and some of the properties of such a mutation. This mutation which maps between genes 52 and t defines a new regulatory gene.
TL;DR: In this paper, a simple procedure is described to calculate the Anderson-Gruneisen parameter from the third-order elastic constants of a crystal and is used to evaluate the same for nine hexagonal metals and for the cubic magnesium oxide (MgO) in all the crystals, with the exception of beryllium.
Abstract: A simple procedure is described to calculate the Anderson-Gr\"uneisen parameter $\ensuremath{\delta}$ from the third-order elastic constants of a crystal and is used to evaluate the same for nine hexagonal metals and for the cubic magnesium oxide (MgO) In all the crystals, with the exception of beryllium, the relation $\ensuremath{\delta}=2\ensuremath{\gamma}$ is very nearly satisfied The relevance of these calculations to the anharmonicity in these crystals is discussed Anderson's theory has been used to explain the temperature dependence of the bulk modulus of the hexagonal metals magnesium, zinc, cadmium, and beryllium and the results are compared with experimental values
TL;DR: Conversation of weight can be defined as the ability to affirm that the weight of an object remains invariant during the transformations of the form of the object as discussed by the authors, which is known to be achieved at a conceptual level at about 9 years of age.
TL;DR: Examination of the proteins synthesized at 43° by one of the temperature-sensitive groE strains, groEA44, by SDS gel electrophoresis reveals a pattern of synthesis somewhat different from that exhibited by the gro+ parent strain: some new bands appear, while others disappear.
Abstract: groE bacterial mutants of E. coli have been isolated on the basis of their inability to propagate bacteriophage λ. The block exerted on λ growth has been shown to operate at the level of head assembly. Some groE mutations express pleiotropic effects, such as inability to propagate T4 and T5 or inability to form colonies at high temperature. P1 transduction experiments show that these groE mutations map at 83 min on the genetic map of E. coli and that a single mutation is responsible for the pleiotropic effects observed. At 43°C, some of the groE strains are temperature sensitive for growth and form long filamentous structures. Examination of the proteins synthesized at 43° by one of the temperature-sensitive groE strains, groEA44, by SDS gel electrophoresis reveals a pattern of synthesis somewhat different from that exhibited by the gro+ parent strain: some new bands appear, while others disappear.
TL;DR: There is considerable evidence that hormone secretion from the neurohypophysis occurs by exocytosis of neurosecretory granules present in the nerve terminals as discussed by the authors, which involves fusion of the granule membrane with the plasma membrane so that the entire soluble content of granule is discharged into the extracellular space.
Abstract: THERE is considerable evidence that hormone secretion from the neurohypophysis occurs by exocytosis of neurosecretory granules present in the nerve terminals1–4. Exocytosis involves fusion of the granule membrane with the plasma membrane so that the entire soluble content of the granule is discharged into the extracellular space. Persistent hormone secretion does not lead to irreversible expansion of the plasmalemma of neurosecretory terminals, so the granule membrane must somehow be retrieved after fusion. There is morphological evidence based on the use of electron dense markers in various preparations, that following exocytosis membrane is returned to the cell interior where it is present as microvesicles and larger cisternae5–10.
TL;DR: The results indicate that plain and complex flagella are entirely different in structure and composition and that the complex type represents a novel flagellar species.
Abstract: Cells of Pseudomonas rhodos 9-6 produce two morphologically distinct flagella termed plain and complex, respectively. Fine structure analyses by electron microscopy and optical diffraction showed that plain flagellar filaments are cylinders of 13-nm diameter composed of globular subunits like normal bacterial flagella. The structure comprises nine large-scale helical rows of subunits intersecting four small-scale helices of pitch angle 25 degrees . Complex filaments have a conspicuous helical sheath, 18-nm wide, of three close-fitting helical bands, each about 4.7-nm wide, separated by axial intervals, 4.7 nm wide, running at an angle of 27 degrees . The internal core has similar but not identical substructure to plain filaments. Unlike plain flagella, the complex species is fragile and does not aggregate in bundles. Mutants bearing only one of two types of flagellum were isolated. Cells with plain flagella showed normal translational motion, and cells with complex flagella showed rapid spinning. Isolated plain flagella consist of a 37,000-dalton subunit separable into two isoproteins. Complex filaments consist of a 55,000-dalton protein; a second 43,000-dalton protein was assigned to complex flagellar hooks. The results indicate that plain and complex flagella are entirely different in structure and composition and that the complex type represents a novel flagellar species. Its possible mode of action is discussed.
TL;DR: The origin of replication in Escherichia coli K-12 was mapped by determining the rate of marker replication during a synchronous round of replication by determined by deoxyribonucleic acid-deoxyrib on nucleic acid hybridization to filters containing Mu-1, lambda, and E. coli deoxy ribonucleics acid.
Abstract: The origin of replication in Escherichia coli K-12 was mapped by determining the rate of marker replication during a synchronous round of replication. Four isogenic strains were made lysogenic for λind− and for phage Mu-1, with Mu-1 integrated into a different chromosomal location in each strain. Cultures were starved for amino acids to allow completion of chromosome replication cycles and then starved for thymine in the presence of amino acids, and a synchronous cycle of replication was initiated by the addition of thymine. Samples were exposed to radioactive thymidine at intervals, deoxyribonucleic acid was extracted, and the rate of marker replication was determined by deoxyribonucleic acid-deoxyribonucleic acid hybridization to filters containing Mu-1, λ, and E. coli deoxyribonucleic acid. The results confirm that the origin of replication is near ilv. The travel times of the replication forks, calculated from the data obtained for cultures with doubling times of approximately 40 and 61 min, are 40 and 52 min, respectively.
TL;DR: Characterization of the plasmids obtained indicates that the replication genes O and P, a regulatory gene cro, and sequences in the operator-promoter region which control the transcription of cro, O and F are important and regulatory genes c I and c II play no indispensable role.
TL;DR: In this article, each of the 50 S ribosomal subunit proteins of Escherichia coli was tested independently in two laboratories for its ability to bind specifically to 23 S RNA.
TL;DR: In this article, a unified description of systems with a condensed phase in terms of hydrodynamic equations of motion is given, and the eigenmodes of the linearized form of these equations, typically first and second sound, are discussed in particular with respect to their manifestation in inelastic light and neutron scattering.
Abstract: A unified description of systems with a condensed phase in terms of hydrodynamic equations of motion is given. These equations are of two kinds: First those equations obeyed by the thermal excitations (the "first fluid") typically are local conservation equations of mass, energy and momentum. Second the equation obeyed by the condensed phase (the "second fluid") is an equation of motion related to the order parameter of the broken symmetry. These equations are established on phenomenological grounds making use of irreversible thermodynamics. The eigenmodes of the linearized form of these equations, typically first and second sound, are discussed in particular with respect to their manifestation in inelastic light and neutron scattering. The systems considered are homogenous superfluids, superconductors, dielectric crystals and magnetic systems. Except for superfluid $^{4}\mathrm{He}$ the critical behavior at the phase transition to the ordered state is not systematically discussed.
TL;DR: The results suggested that Py-induced replication of the mouse cell chromatin may be necessary to provide replicating Py DNA with histones and that complex B becomes the "core" of progeny Py virions.
Abstract: Polyoma viral DNA is shown to be replicated in close association with the mouse cell chromatin. Two virus-specific nucleoprotein complexes, designated complex A and B, can be dissociated from the isolated chromatin by gentle homogenization in 0.5 M NaCl. Complex A contains only replicating polyoma (Py) DNA whereas complex B contains only mature Py DNA I. The results show, furthermore, that complex A, containing viral DNA in different stages of replication, and complex B are both nucleoproteins with the same buoyant density. The data presently available suggest that newly synthesized stretches of Py DNA are immediately complexed with mouse cell histones and that complex B becomes the “core” of progeny Py virions. These results suggested that Py-induced replication of the mouse cell chromatin may be necessary to provide replicating Py DNA with histones.
TL;DR: In this paper, a simple procedure to evaluate the Anderson-Gruneisen parameter for cubic crystals from third order elastic constants data is presented and applied to ten cubic compounds, and it is shown that the parameter can be applied to any cubic compound.
TL;DR: Durch HistofluoreszenZ-Methode f for Monoamine wurde nachgewiesen, dass die Abnahme der grünen Fluoreszenz in den Noradrenalin-Endungen des Cortex and Hypothalamus im Rattenhirn durch α-Methyl-Paratyrosin verstärkt wird.
Abstract: Durch Histofluoreszenz-Methode fur Monoamine wurde nachgewiesen, dass die Abnahme der grunen Fluoreszenz in den Noradrenalin-Endungen des Cortex und Hypothalamus im Rattenhirn durch α-Methyl-Paratyrosin verstarkt wird, was vermuten lasst, dass dieses Tripeptid die Freisetzung und Umkehrung des Noradrenalin erhoht.
TL;DR: Conidia ofNeurospora crassa shaken in liquid cultures at 46°C for 15 h and then shifted-down to 25°C germinate directly into conidiophores producing new conidia (macroconidia).
Abstract: Conidia ofNeurospora crassa shaken in liquid cultures at 46°C for 15 h and then shifted-down to 25°C germinate directly into conidiophores producing new conidia (macroconidia).
TL;DR: Findings serve to localize the sites at which proteins incapable of independent interaction with 16 S RNA are fixed during the early stages of 30 S subunit assembly.
TL;DR: The vitellogenesis in Bothriocephalus clavibothrium was studied by means of histochemistry and electron microscopy methods and the rôle of those products synthesized and accumulated by viteLLine cells is discussed.
Abstract: La vitellogenese de Bothriocephalus clavibothrium a ete etudiee par histochimie et microscopie electronique.
TL;DR: In this article, it was shown that the adsorption of fluoride ions at the membrane-solution interface and the solubility of the electrode crystal are the two principal parameters limiting the sensitivity of the fluoride-selective electrode.
TL;DR: In this article, the superconducting transition temperature has been investigated as a function of composition and degree of long-range order in a number of binary and ternary A 15-type phases on Cr and Mo.