Showing papers by "Collège de France published in 1975"
TL;DR: In this paper, the behavior of a single flexible polymer chain near the Flory temperature Θ is analyzed in analogy with a magnetic phase transition, and the transition to a collapsed state is related to a tricritical point for the magnetic problem.
Abstract: The behavior of a single, flexible polymer chain near the Flory temperature Θ is analysed in analogy with a magnetic phase transition. The transition to a collapsed state is related to a tricritical point for the magnetic problem.
427 citations
TL;DR: It is concluded that haemopoietic stem cells of the definitive blood cell series originate from some source other than the yolk-sac, and that this source must be intra-embryonic.
Abstract: It is currently accepted that stem cells of the definitive blood cell lines originate from the yolk-sac blood islands. Experiments were devised to examine the validity of this theory in the avian embryo. These involved grafting two-day-old quail embryos on to chick yolk-sacs of comparable developmental stages, i.e. before or shortly after the establishment of vascularization. The conclusions of the experiments are based on the possibility of distinguishing chick cell nuclei from those of the quail. In the developing haemopoietic organs (spleen and thymus) of quail embryos grafted on to the chick and subsequently incubated for 6-11 days, all cells, whether belonging to the granulopoietic, erythropoietic or lymphopoietic series, are of quail type. Thus these organs have not been colonized by chick stem cells. On the other hand, coelomic graft experiments show that the development of these organs is indeed dependent on an extrinsic colonization by haemopoietic cells; quail spleen or thymus rudiment, developing in the coelom of a chick is populated by chick cells. Thus no incompatibility which would prevent heterospecific colonization exists in this system. It is concluded that haemopoietic stem cells of the definitive blood cell series originate from some source other than the yolk-sac, and that this source must be intra-embryonic.
417 citations
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210 citations
TL;DR: In this article, the incoherent scattering law for neutron quasi-elastic scattering in liquid crystals is calculated using a classical formalism including (anisotropic) self-diffusion, rotational motion along the long molecular axis and short time vibrational behaviour.
Abstract: The incoherent scattering law for neutron quasi-elastic scattering in liquid crystals is calculated using a classical formalism including (anisotropic) self-diffusion, rotational motion along the long molecular axis and short time vibrational behaviour. Explicit expressions are given for oriented as well as for unoriented liquid crystals.
179 citations
TL;DR: It is concluded that in addition to PCT and PR, CAL and BCT might be target structures involved in the physiological actions of PTH on the kidney.
Abstract: PTH sensitive adenylate cyclase activity was measured in 9 different segments of the nephron, isolated by microdissection from collagenase-treated rabbit kidney slices.
169 citations
TL;DR: The functional organization of visual cortical cells was studied in two groups of five week old kittens: one group normally reared, the other reared in total darkness from the third day after birth.
Abstract: The functional organization of visual cortical cells was studied in two groups of five week old kittens: one group normally reared, the other reared in total darkness from the third day after birth. The following results were obtained:
1.
The cells of the normally reared kittens were similar to adult cells except for some aspects of immaturity. In contrast, the cells of the dark-reared kittens were totally non-specific. Their receptive field showed neither orientational nor directional properties.
2.
The distribution of cells according to the ocular dominance was not different in either group and was similar to that previously described for ‘adult’ cells.
3.
A few hours of visual experience was sufficient to provide specific receptive field properties to the cortical cells of a dark-reared kitten.
4.
Conditioning exposure with an oriented grating induced changes in orientational sensitivity in normally reared kittens but not in dark-reared kittens.
145 citations
TL;DR: The limited response obtained in DCT as well as the clearcut effect elicited by AVP in MAL (the functioning of which is not known to be controlled by ADH) were unexpected observations; their possible physiological implications will be discussed.
Abstract: AVP dependent adenylate cyclase activity was measured in single pieces of 8 different tubular segments isolated from collagenase treated rabbit kidneys.
118 citations
TL;DR: In this paper, a methodologie generale de traitement des problemes de controle impulsionnel, fondee sur l'etude systematique des inequations quasi variationnelles, is presented.
Abstract: On presente dans cet article une methodologie generale de traitement des problemes de controle impulsionnel, fondee sur l'etude systematique des inequations quasi variationnelles Celles-ci jouent pour le controle impulsionnel un role analogue a celui des equations de Hamilton-Jacobi-Bellman pour le controle continu
112 citations
TL;DR: In this article, a Hamiltonian embedding is proposed for Nambu's new mechanical equations, which is studied in classical and quantized versions, utilizing Dirac's singular formalism.
Abstract: Hamiltonian embedding is proposed for Nambu's new mechanical equations. This embedding is studied in classical and quantized versions, utilizing Dirac's singular formalism. Nambu's canonical transformations are then compared with those of the embedding Hamiltonian.
110 citations
TL;DR: The method described appears to be suitable to determine which nephron segments contain hormone-dependent adenylate cyclase, and as a function of the length of the segment used, which was found to be a few fentomoles (10−15 M) cAMP.
Abstract: A method is described, which allows adenylate cyclase activity measurement in single pieces of various nephron segments. Tubular samples of 0.5 to 2 mm length were isolated by microdissection from collagenase treated slices of rabbit kidney. A photograph of each piece was taken in order to measure its length. After a permeabilisation treatment involving preincubation in a hypoosmotic medium and a freezing step, each sample was incubated for 30 min at 30°C in a medium containing high specific [α-32P]-ATP 3·10−4 M, final volume 2.5 μl.
104 citations
TL;DR: It is postulated that a long term adaptation of the striatal cholinergic neurons may have occurred after complete degeneration of the nigrostriatal DA pathway, and changes in ACh levels, which have been shown to be a good index of dopamine levels, argue against an inhibitory dopaminergic influence on the striato-cholinergic system.
TL;DR: Male rats were given a quinine adulterated fluid as their sole source of liquid for over 60 days, and after a latency of a few days, fluid intake stabilised at about 20 ml/day, with the water to food ratio close to 1.0 ml/g.
TL;DR: The presence of catecholamine-dependent AC activity in three distal portions of the rabbit nephron is discussed in relation to its possible physiological implications.
Abstract: The sensitivity to catecholamines of the adenylate cyclase (AC) activity contained in single tubule samples was investigated on 10 different well defined segments, isolated by microdissection from collagenase treated rabbit kidneys.
TL;DR: In this article, a relativistic generalization of the harmonic oscillator is presented, which admits a Poisson bracket form, analogous to Heisenberg evolution equations, leading to the equations of motion.
01 Jan 1975
TL;DR: Differences in the intraneuronal distribution of the monoamines reveal the existence of several morphologically distinct “pools” or “compartments” of monoamines.
Abstract: Norepinephrine (NE), dopamine (DA), and serotonin (5-HT) are probably neurotransmitters at a number of important synapses in the central nervous system. The amines can be synthesized locally in the cell bodies, axons, and numerous varicosities or “synapses en passage” of aminergic neurons. According to estimates made on peripheral adrenergic neurons, which are probably similar for neurons in the CNS, the concentrations of transmitter in the terminal varicosities are very much higher (approximately 10,000 μg/g) than in the cell bodies (10–100 μg/g) or in the preterminal axons (10–1500 μg/g) (Norberg and Hamberger, 1964). These important differences in the intraneuronal distribution of the monoamines reveal the existence of several morphologically distinct “pools” or “compartments.” In addition, the amine localized in the synaptic varicosities, which are regularly spaced in the terminal arborizations of the axons, is the only form that can be liberated in response to nerve activity and is thus distinguished by a functional criterion from the other intraneuronal forms of monoamines.
TL;DR: The ultra-structural study enabled us to identify these cell types, to describe their spatial relationships, and to follow their evolution with time in culture, to identify primitive neuro-epithelial cells and typical neurosecretory cells.
Abstract: Dissociated fetal hypothalamic cells mainly taken from 14 day-old mouse fetuses were grown in vitro for increasing time (9 to 60 days). Soon after inoculation the cells partly reaggregated and attached. The small reaggregates were then interconnected by fibers bundles. After the first week the cultures were composed of a continuous basal monolayer of flat and transparent cells, over which various types of refractile cells were lying in discontinuous areas. The ultra-structural study enabled us to identify these cell types, to describe their spatial relationships, and to follow their evolution with time in culture.
TL;DR: In this article, the authors consider a restricted problem in irreversible melting, where a onesingle boundary (separating a coil region from a helical region) moves through the chemical sequence, and the distribution function for the boundary point is then ruled by a simple Fokker-Planck equation.
Abstract: We discuss some properties of the one-dimensional Fokker-Planck equation, and in particular the time required to go through a potential barrier of arbitrary size and shape. We apply the resulting formulas to the melting of helical polymers made of two types of monomers (A and B) with different melting temperatures: We consider a restricted problem in irreversible melting, where onesingle boundary (separating a coil region from a helical region) moves through the chemical sequence. In a crude approximation the distribution function for the boundary point is then ruled by a simple Fokker-Planck equation. When the temperatureT is equal to or higher than the average melting point¯T, the boundary tends to move over macroscopic distances, thus extending the size of the coil regions. In an interval¯T T* essentially all barriers are overcome and the progression is fast.
TL;DR: Observations suggest that the frog skin epithelium contains 2 separated but communicating compartments having different degrees of accessibility from outside, and only that compartment filling at a fast rate is involved in the transepithelial Na transport.
Abstract: Experimental conditions are described in which transient and positive current responses across isolated frog skin epithelia can be elicited by sudden addition of Na and Li ions (2–40 mM) in the outer bathing solution. Subsequent return to outer Na (or Li) free conditions produce similar transient current changes but in the opposite direction. Analysis of the curve responses shows that the transient component of each curve is best described by a single, fast exponential term equation in case of Na addition to preparation unpoisonned with ouabain. In contrast, an equation including two exponential terms (a fast and a slow one) is required to fit the curve responses observed across ouabain treated epithelia of if Li is added outside. The transient responses were not significantly altered by substituying Cl for SO4
2− anions. They were completely prevented by Amiloride (5 · 10−5 M), increased by oxytocin (20 mU/ml) and markedly dependent upon the outer Na concentration. Interpreted in term of compartmental analysis, these observations suggest that a) the frog skin epithelium contains 2 separated but communicating compartments having different degrees of accessibility from outside; b) only that compartment filling at a fast rate (0.5 min) is involved in the transepithelial Na transport; c) the other one, filling at a rate of 4 to 7 min, is resplenished only under conditions where the basal pump system has a reduced activity. Tentative localization of these compartment is proposed.
TL;DR: The enzyme ChAc was recently purified from rat brain by a modified procedure of that previously described, and the specific activity was considerably higher than those previously reported for ChAc from vertebrates, but the enzyme was not completely pure as revealed by polyacrylamide gel electrophoresis at pH 4.3 and SDS gels.
TL;DR: In this article, the authors consider a solid/nematic interface where long range van der Waals torques favor homeotropic alignment, while a direct steric effect tends to induce a planar alignment.
Abstract: We consider a solid/nematic interface where long range van der Waals torques favor homeotropic alignment, while a direct steric effect tends to induce a planar alignment. Depending on the relative strength of the two contributions, one may find two transitions : planar ↔ conical and conical ↔ homeotropic. This is reminiscent of recent observations by Ryschenkow and Kleman on glass surfaces coated with carbon black. Similar local Frederiks transitions could occur by competition between two distinct planar arrangments.
TL;DR: The reaction of a chiral compound R on each of enantiomers which constitute a mixture of optical purity p, is characterized by rate constants whose ratio K often may be evaluated experimentaly as discussed by the authors.
TL;DR: Anterior pituitary continuous cell lines were found to be a useful model for the analysis of mechanisms of action of agents that quantitatively regulate their hormonal secretion.
Abstract: Publisher Summary This chapter discusses a cell culture approach to study the anterior pituitary cells. Pituitary cells maintained in vitro for months or years differ from pituitary organ cultures in which tissue organization is maintained, and from tissue culture starting from small fragments of tissue which grow and can display selection in some cell populations. Among cell cultures one must distinguish (1) primary cultures that start from normal adult fully differentiated anterior pituitary cells, and (2) continuous cell lines that consist of homogeneous populations of pituitary glandular cells which continuously grow in vitro. The chapter discusses the functional and morphological features of pituitary cells grown in these two situations. The effects on these models of factors that regulate the secretion of anterior pituitary hormones are analyzed and discussed. Anterior pituitary continuous cell lines were found to be a useful model for the analysis of mechanisms of action of agents that quantitatively regulate their hormonal secretion. In several cases they appear to be very close to the in vivo situation, e.g., control of prolactin (PRL) secretion by TSH-releasing hormone (TRH) and estrogens, control of growth hormone secretion by thyroid hormone, and control of adrenocorticotropic hormone (ACTH) secretion by glucocorticoids. Because of their cellular homogeneity, they have the advantage in regard to primary culture of allowing investigations at the molecular level, which are undergoing rapid progress.
01 Jan 1975
Journal Article•
TL;DR: High-affinity choline transport system in rat striatal synaptosomes was inhibited competitively by a series of long-chain alkyl bisquaternary ammonium compounds, and choline-related analogues yielded the following findings.
Abstract: The high-affinity choline transport system in rat striatal synaptosomes was inhibited competitively by a series of long-chain alkyl bisquaternary ammonium compounds. BTE18 [octadecamethylenebis(triethylammonium bromide)] had a Ki value of 28 nM, and BHDM18 [octadecamethylenebis((2-hydroxyethyl)dimethylammonium bromide)] had a Ki value of 75 nM. BTE18 and hemicholinium-3 (HC-3) were equipotent competitive inhibitors. The transport of neither tryptophan nor dopamine was inhibited significantly by these compounds. Inhibitory activity increased as the alkyl chain length was increased, but reached a maximum at 17 or 18 methylene groups for bistriethyl- and bistrimethylammonium compounds. Triethylammonium compounds were more active than trimethylammonium compounds. Monoquaternary alkyltrimethylammonium compounds with 5-12 methylene groups were at least as active as the corresponding bis compounds. Various other choline-related analogues yielded the following findings. Hemicholinium-15 was much less active than HC-3. Troxonium and troxypyrrolium tosylate were moderately effective inhibitors, as was the cholinesterase inhibitor BW 284 C51. Long-chain alkyl bisquaternary ammonium compounds may be useful high-affinity analogues in studying the properties of this synaptosomal choline transport system.
TL;DR: Evidence is presented for the presence of an endogenous inhibitor of tryptophan hydroxylase, which was inhibited by the chelating agents 8‐hydroxyquinoline, O‐phenanthroline and EDTA in pig brain purified using a method which involved sonic disintegration of a whole homogenate and ammonium sulphate fractionation.
Abstract: —Tryptophan hydroxylase form pig brain has been purified using a method which involved sonic disintegration of a whole homogenate, ammonium sulphate fractionation, hydroxylapatite fractionation, column chromatography on Sephadex G-100 or G-200 and finally electrophoresis on poly-acrylamide gel. The enzyme was stabilized during purification by tryptophan and dithiothreitol. The partially purified enzyme has a molecular weight of 55,000-60,000 as measured by gel-filtration. The Km of the soluble partially purified enzyme was 0-4 mm, which differed significantly from that of the particulate enzyme (0·02mm). Enzyme activity was not stimulated by ferrous ion. However, it was inhibited by the chelating agents 8-hydroxyquinoline, O-phenanthroline and EDTA. In contrast to dopamine, high concentration of tryptophan (10 mm), 5-hydroxytryptamine, tryptamine and tyramine at 0-5 mm concentration did not inhibit the enzyme in the presence of dimethyltetrahydropterin (DMPH4). A number of monoamine oxidase inhibitors, phenelzine, pheniprazine and chlorgyline at 1 mm strongly inhibit the formation of 5-hydroxytryptamine. Evidence is presented for the presence of an endogenous inhibitor of tryptophan hydroxylase.
TL;DR: It is found that octopine dehydrogenase, relative to other dehydrogenases, is provided with a rather low delta H not equal to, which enables the enzyme to change its turnover number by only a small factor in the temperature range 5--35 degrees C.
Abstract: We investigated the temperature dependence of several functions of octopine dehydrogenase, a monomeric enzyme extracted from the shell fish Pecten maximus L. We found that six enzymatic functions are temperature independent or change only negligibly with temperatue. These are the dissociation constants of three coenzyme complexes and the Michaelis Km values for NAD, NADH and one of the substrates (D-octopine). This is taken as an indication of a temperature-regulatory mechanism which enables the enzyme to maintain a constant level of NAD, NADH and D-octopine in binary and ternary complexes independent of fluctuations of the external temperature. This is discussed with reference to enzymes from other poikilotherms, which reportedly display similar biologically meaningful response to temperature. We also discuss the meaning of our data from a thermodynamic viewpoint. Considering that in a temperature-independent binding process only entropy changes contribute to the standard free-energy change, we speculate on possible molecular models which might account for our results. We also investigate the activation-energy parameters for the reaction catalyzed by octopine dehydrogenase, as obtained from the temperature dependence of V. It is found that octopine dehydrogenase, relative to other dehydrogenases, is provided with a rather low delta H not equal to, which enables the enzyme to change its turnover number by only a small factor in the temperature range 5--35 degrees C.
TL;DR: This kinetic study demonstrated a rapid intracellular transit of newly synthesized prolactin (15 + 10 min or less), the existence of at least two intrACEllular prolactIn pools, and a delayed stimulating effect of TRH on Prolactin synthesis.
01 Jan 1975
TL;DR: This work has shown that acetylcholine can be isolated in the test tube using a variety of methods, and its pharmacological action on various categories of cells has received considerable attention for almost a century.
Abstract: Acetylcholine is one of the best-known neurotransmitters and its pharmacological action on various categories of cells has received considerable attention for almost a century. Until recently, however, many pharmacologists doubted that its “receptive substance” would ever be isolated in the test tube. Indeed, lipids, polysaccharides, proteins, and even nucleic acids were equally considered as potential receptors, but definitive proof that any one of these compounds accounts for the physiological action of acetylcholine was consistently missing. The difficulty rested on the lack of a firm theory and a reasonable method of characterization and isolation.
TL;DR: In this article, auteurs rapportent un cas de "surdite corticale" where le patient etait dans l'incapacite totale d'identifier le langage oral, les bruits familiers et la musique, alors qu'il n'y avait pas d'alteration notable des seuils a l'audiometrie courante.