Showing papers by "Université libre de Bruxelles published in 1972"
TL;DR: A cortical band of fine microfilaments is consistently observed in the beta cells of the rat pancreas and Alteration of this cell web by cytochalasin B is associated with an enhancement of glucose-induced secretion of insulin by isolated islets.
Abstract: A cortical band of fine microfilaments is consistently observed in the beta cells of the rat pancreas. Alteration of this cell web by cytochalasin B is associated with an enhancement of glucose-induced secretion of insulin by isolated islets. The microfilamentous web of the beta cell may play an important role in the emiocytosis of insulin secretory granules, by controlling their access to the cell membrane.
353 citations
TL;DR: Five combinations of antibiotics investigated in vitro and in 148 severe infectious episodes caused by gram-negative bacilli in patients with disseminated cancer found that the use of combinations that were synergistic in vitro against the offending microorganism was associated with a significantly better response to antibacterial therapy.
Abstract: Five combinations of antibiotics (ampicillin/gentamicin, cephalothin/gentamicin, carbenicillin/gentamicin, polymyxin/carbenicillin, and carbenicillin/cephalothin) were investigated in vitro and in 148 severe infectious episodes caused by gram-negative bacilli in patients with disseminated cancer. The use of combinations that were synergistic in vitro against the offending microorganism (synergy was defined as occurring when the minimal inhibitory concentration of each of the drugs in the combination was one-quarter or less of the minimal inhibitory concentration of each drug alone) was associated with a significantly better response to antibacterial therapy (P < 0.01) than the use of combinations that were not synergistic against the causative agent.
188 citations
TL;DR: In this paper, the tensile yield stress was compared with the uniaxial compression yield stress for specimens of polycarbonate tested at constant strain rate from −120 to + 120°C.
Abstract: The tensile yield stress is compared with the uniaxial compression yield stress for specimens of polycarbonate tested at constant strain rate from −120 to + 120°C. The strain rate dependence of the tensile yield stress is also studied from − 140 to + 20°C.
162 citations
TL;DR: In this paper, the authors proposed a yield mechanism based on the assumption that the β process considered in the Ree-Eyring theory and the loss peak revealed by oscillatory measurements are related to the same molecular movements.
Abstract: The compression yield behaviour of polycarbonate, at constant strain-rate, over a wide range of temperatures, is described by the Ree-Eyring theory of non-Newtonian viscosity linked with a treatment which takes into account a distribution function of activation energies. The proposed yield mechanism relies on the assumption that theβ process considered in the Ree-Eyring theory and the loss peak revealed by oscillatory measurements are related to the same molecular movements. A relation is given between theβ transition conditions in yield measurements and in damping tests; its validity is checked. The broadness and the shape of theβ loss peak are correlated with a spectrum of activation energies. The compression yield-stress curve, giving the yield stress versus temperature at constant strain-rate, is computed from the measurements of the loss tangent, as a function of temperature, at the frequency corresponding to the strain-rate and is found to fit the data fairly well.
119 citations
TL;DR: It is suggested that neural mechanisms are at the origin of both the high frequency variations and the circadian phenomenon, this latter being related to the sleep-wake cycle.
Abstract: The existence of circadian variations in serum TSH levels was investigated in 8 normal subjects. The analysis of the data indicated the presence of 2 different reproducible phenomena, a circadian rhythm characterized by an important acrophase and lower amplitude higher frequency variations, with period between 1 and 3 hours. It is suggested that neural mechanisms are at the origin of both the high frequency variations and the circadian phenomenon, this latter being related to the sleep-wake cycle. A significant difference, between nocturnal and diurnal mean TSH levels was observed in women, but not in men.
118 citations
TL;DR: The presence of binding sites between the membranes of the sarcoplasmic vesicles and a glycogen-enzyme complex suggests that this association plays a role in the glycogenolysis during muscle contraction.
Abstract: Sarcoplasmic vesicles and s-glycogen particles 30–40 mµ in diameter were isolated from perfused rabbit skeletal muscle by the differential precipitation-centrifugation method. This microsomal fraction was subjected to zonal centrifugation on buffered sucrose gradients, in a B XIV Anderson type rotor, for 15 hr at 45,000 rpm in order to separate the two cytoplasmic organelles. Zonal profiles of absorbance at 280 mµ, proteins, glycogen, and enzymatic activities (phosphorylase b kinase, phosphorylase b, and glycogen synthetase) were performed. Whereas the entire synthetase activity was found combined with the glycogen particles, 39% of phosphorylase and 53% of phosphorylase b kinase activities, present in the microsomal fraction, were recovered in the purified vesicular fraction (d = 1.175). This latter fraction consists of vesicles, derived from the sarcoplasmic reticulum, and of small particles 10–20 mµ in diameter attached to the outer surface of the membranes. These particles disappear after α-amylase treatment. Incubation of the sarcovesicular fraction with 14C-labeled glucose-1-phosphate confirms the localization of a polysaccharide synthesis at the level of the membranes. "Flash activation" of phosphorylase b, i.e. Ca "activation" of phosphorylase kinase followed by a conversion of phosphorylase b into a, was demonstrated in the purified sarcovesicular fraction. Moreover, the active enzymatic sites were detected on the membranes by electron microscopy. The presence of binding sites between the membranes of the sarcoplasmic vesicles and a glycogen-enzyme complex suggests that this association plays a role in the glycogenolysis during muscle contraction.
118 citations
TL;DR: The results confirmed observations from the literature about the existence of an atypical proliferation zone in polyps and observed that, in the polyps, the turnover time is sharply reduced if compared with remote healthy tissue.
109 citations
TL;DR: In this paper, the theory of nonequilibrium fluctuations in open systems is extended to nonlinear situations, and it is shown that the usual birth-and-death type of stochastic formulation of chemical kinetics is in general inadequate and has to be replaced by a more detailed phase-space description.
Abstract: The theory of nonequilibrium fluctuations in open systems is extended to nonlinear situations. It is shown that the usual birth-and-death type of stochastic formulation of chemical kinetics is in general inadequate and has to be replaced by a more detailed phase-space description. As a consequence, for large classes of nonlinear systems arbitrarily far from equilibrium, the classical Einstein fluctuation formula can be extended, provided the steady reference state is asymptotically stable. The case of oscillatory or unstable systems is also discussed. It is conjectured that in such systems, the departure from the steady state is governed by large fluctuations of “macroscopic” size, while small fluctuations are still described by the extended Einstein formula. Nonequilibrium macroscopic instabilities such as chemical or hydrodynamic instabilities seem therefore to bear strong similarities to first-ordei phase transitions.
106 citations
TL;DR: In this paper, it was shown that the NADPH-linked glutamic dehydrogenase (anabolic GDHase) plays a key role in the regulation of nitrogen catabolism.
103 citations
TL;DR: In this paper, the standard potential of the O 2 −0.270 V/NHE system has been determined by comparing the data obtained by pulse polarography and reoxidation chronocoulometry.
102 citations
TL;DR: In this paper, a bacterial mutation ( ron ) has been isolated which prevents growth of some λ lines, which are found to carry a mutation in the N gene, mar, which remains undetected in ron + strains.
TL;DR: It is suggested that both microfilaments and microtubules are required for the TSH-stimulated thyroid secretion process: the first (microfilaments) as active contractile agents would constitute newly formed pseudopods; the more passive microtubule would play a role of scaffolding in the cells and in the pseudopod, thus supporting the pseudipods in the engulfing process.
TL;DR: Several new deletions of the λ prophage have been mapped, permitting the localization of sites in the κ genome for initiation of replication, for initiationof gene c I function and for the response to regulation by gene cro.
Abstract: Several new deletions of the λ prophage have been mapped, permitting the localization of sites in the λ genome for initiation of replication, for initiation of gene c I function and for the response to regulation by gene cro.
TL;DR: Tracheotomized patients, with severe underlying illnesses and serious tracheobronchial infections due to gram-negative bacilli were treated at random with intramuscularly or endotracheally administered gentamicin (240 mg daily).
TL;DR: Although 90% of the patients in this series had very extensive tumoral spread beyond any possibility of cure by today's antineoplastic therapy, it is believed that supportive care, aimed at the prevention and treatment of infection in such patients might improve their chance for longer survival.
TL;DR: Histologic sections of the adenohypophyses of humans and rhesus monkeys were examined by differential staining methods and by an immunofluorescent procedure and the same cells showed affinity for the fluorescent immune serum to hGH.
Abstract: Histologic sections of the adenohypophyses of humans and rhesus monkeys were examined by differential staining methods and by an immunofluorescent procedure. In addition, the concentrations of prolactin and growth hormone (GH) in the adenohypophyses of the monkeys were estimated by disc electrophoresis and densitometry, and cell counts were performed on differentially-stained histologic sections. All of the glands examined had numerous somatotropes, which stained with orange G, and the same cells showed affinity for the fluorescent immune serum to hGH. The glands of the pregnant and postpartum women and of all the adult monkeys (lactating or nonlactating) contained prominent erythrosinophils (lactotropes) and these bound the fluorescent antiserum to ovine prolactin. The erythrosinophils did not react with the fluorescent antiserum to hGH and the orangeophils did not localize the fluorescent immune serum to ovine prolactin. The lactotropes were particularly numerous and hypertrophied in the lactating monke...
TL;DR: Analysis of spatial distribution of the labelled parietal cells in the glandular tube indicated that, in time, most newly formedParietal cells undergo a slow migration directed downwards to the bottom of the fundic glands.
Abstract: With autoradiography after labelling with tritiated thymidine, the kinetics of zymogen and parietal cells were studied in the gastric mucosa of mice. After one intraperitoneal injection of the DNA precursor, zymogen cells in the DNA synthesis phase were clearly identified on autoradiograms, whereas no parietal cells were seen to synthesize DNA. In another group of mice, multiple injections were used in order to obtain a greater number of labelled cells. Following the latter procedure, analysis of grain count distributions over labelled zymogen cells and of labelling indices allowed detection of two subsequent zymogen cell divisions within an interval of approximately two months. This indicates that the cell turnover of zymogen cells is at least partly assured by their own mitotic activity. By contrast, parietal cells showed no evidence of cell division, but appeared to be derived through differentiation from other cells in the neck area of the gland. Analysis of spatial distribution of the labelled parietal cells in the glandular tube indicated that, in time, most newly formed parietal cells undergo a slow migration directed downwards to the bottom of the fundic glands. These results clearly show that the zymogen and the parietal cell population of the fundic glands have a different kinetic behaviour.
TL;DR: Further evidence is brought in of the arrest by colchicine of the axonal flow of secretory granules without apparent changes of the neurotubules.
Abstract: The axonal flow of neurosecretory elementary granules has been studied in the paraventricular neurons of the rat (PVN), with the help of three techniques: light microscopy, radioautography after labelling with 35S-L-cysteine, and electron microscopy. Colchicine treatment does not alter the uptake of 35S cysteine in the PVN but the flow of labelled neurosecretory material towards the neurohypophysis is interrupted. Interruption of the axonal flow is also evidenced by the stagnation of neurosecretory granules at the periphery of the neuronal cytoplasm and by the presence of numerous axonal swellings, heavily loaded with neurosecretory granules and often containing abnormal elongated granules, surrounded by a single membrane, oriented more or less parallely to the long axis of the axons. Other cell organelles and neurotubules are not altered. The present experiments bring further evidence of the arrest by colchicine of the axonal flow of secretory granules without apparent changes of the neurotubules.
TL;DR: A male infant, born in June 1964, after a full-term uncomplicated pregnancy from parents who were first cousins, showed a moderate thoracic deformity and a marked bilateral genu valgum and psychological development was normal.
Abstract: G. S., ;I male infant, was born in June 1964, after a full-term uncomplicated pregnancy from parents who were first cousins. His birth weight was 4.0 kg. The first weeks after he was discharged from the hospital, growth was poor; blood examination revealed anemia at the age of 2 ' i P months. Bone marrow examination was normal and he was given iron therapy for a few weeks. Afterwards, he did well; growth followed the tenth percentile and psycho-motor development was normal. At the age of two, an X-ray taken after a fall, disclosed osteopetrotic bones. Similar investigations of the parents and of the two other children did not show any abnormality. From the age of three, the child experienced short periods of unexplained apathy. At the age of four, laboratory data showed values of acidbase equilibrium consistent with strong metabolic acidosis and the child was admitted to the University Pediatric Center. Height was 97 cm and weight 15.3 kg (both just below the tenth percentile). Physical examination showed a moderate thoracic deformity and a marked bilateral genu valgum. Neither hepatosplenomegaly. nor abnormal neurological signs were present. Psychomotor development was normal. Laboratory data were as follow: pH 7.14, 7.09, 7.17; total blood C 0 2 content (t CO,) 15.9, 10.2, 14.7 mmol/l; creatinine 0.73 mg/100 ml; urea 34 mg/100 ml; Na 131 mEq/l; K 3.6 mEq/l; C1 114 mEq/l; P 6.8 mg/100 ml; Ca 9.3 mg/ 100 ml. Urinary pH was markedly high (6.50 to 7.10).
TL;DR: In this paper, two classes of regulatory mutations affecting the synthesis of the carbamoylphosphate synthetase belonging to the arginine biosynthetic pathway have been selected in Saccharomyces cerevisiae.
TL;DR: A highly significant correlation was found between fasting plasma phosphate and TmPO4/U of GFR in the acromegalics, the normal children, the adult controls and also when all groups were pooled.
Abstract: Glomerular filtration rate (GFR),maximal tubular reabsorption of phosphate (TmPO4), and fasting plasma phosphate have been measured in states of normal growth (childhood) and pathological growth (“active” acromegaly, pituitary dwarfism) and in adult controls. GFR and TmPO4 were corrected for a mean body area of 1 m2 73. GFR, TmPO4 and TmPO4/U of GFR were higher in active acromegalics than in adult controls and successfully treated acromegalics. TmPO4 and TmPO4/U of GFR were higher in normal children than in adult controls. GFR was not significantly different. GFR and TmPO4 were lower in pituitary dwarfs than in normal children, whereas TmPO4/U of filtrate was not significantly different. Fasting plasma phosphate was significantly higher in “active” acromegaly and normal children than in adult controls. A highly significant correlation was found between fasting plasma phosphate and TmPO4/U of GFR in the acromegalics, the normal children, the adult controls and also when all groups were pooled. It is conclu...
TL;DR: In this article, the emission spectra of polyacenaphthylene and polyvinylnaphthalene (PVN) films and solutions have been compared at room temperature and 77°K.
TL;DR: For well defined ranges of values of certain parameters such systems may exhibit transitions between several stable steady states, and the thermodynamic aspects of such transitions are discussed within the framework of the recent theory of dissipative instabilities.
TL;DR: In this paper, a review of the present knowledge on the thermodynamics and kinetics of electrochemical corrosion in the presence of electrolytes (aqueous solutions, molten salts, etc.) and of gaseous atmospheres is given.
TL;DR: Four successive phases during the growth of an oocyte can be distinguished with respect to the ribosomal system.
Abstract: Xenopus laevis tadpoles and toads were killed at several ages. The structure of the nuclei of the germinal cells has been observed by light and electron microscopes. We distinguish 11 successive stages in nucleolar structure: (1) a single, essentially granular nucleolus in the oogonium (10 µm diameter), (2) a reticulated nucleolus in the leptotene oocyte, (3) fragmentation of this nucleolus into a few smaller nucleoli, (4) multiple tiny nucleoli appearing in the cap of the pachytene oocyte, (5) enrichment in the fibrillar constituent of these intra-cap nucleoli, (6) grouped spherical nucleoli, with well segregated granular and fibrillar constituents, as the disintegration of the cap is going on (diplotene A oocyte, 30 µm diameter), (7) dispersion of those nucleoli in the nuclear sap (diplotene B oocyte, 50 µm diameter), (8) formation of long, ribboned nucleoli with multiple DNA-rich spots (diplotene C oocyte, 100 µm diameter), (9) fragmentation of the nucleolar ribbons into multiple spherical nucleoli with excentric fibrillar core and granular cortex (diplotene D oocyte, 150 µm diameter), (10) multiple purely fibrillar nucleoli (diplotene E oocyte, between 150 and 400 µm diameter), and (11) multiple classical nucleoli with concentric fibrillar core and granular cortex (diplotene F oocyte, between 400 and 1000 µm diameter).
The multiplication of the nucleoli in Xenopus laevis may occur successively ( a ) by the fragmentation of the single oogonium nucleolus at the leptotene stage, ( b ) by de novo formation of nucleolar bodies inside the cap at the pachytene stage, and ( c ) by the growth of those nucleoli lying free in the nucleolar sap at the early diplotene stage. They evolve into nucleolar ribbons which later on fragment into spherical bodies.
Four successive phases during the growth of an oocyte can be distinguished with respect to the ribosomal system. (I) The first phase is characterized by the nucleolar DNA amplification. (II) During the second phase, the multiplication of the nucleoli is going on. Ribosomes are present in the cytoplasm and the rate of cellular growth is very high. (III) During the third phase, the synthesis of rRNAs seem to be repressed while the synthesis of heterogenous small RNAs is going on. Ribosomes are no longer visible in the cytoplasm. The nucleoli are purely fibrillar. The rate of cell growth is lower than in the preceding phase. (IV) During the fourth ( = Duryee lampbrush stages 3-6), or vitellogenic phase, rRNAs are actively synthesized and numerous ribosomes appear in the cytoplasm. The nucleoli have the classical structure and the rate of growth is about the same as during phase III.
TL;DR: The investigations of Jacob and Monod and Novick and Weiner have shown that at the cellular level, the induction of ~-galactosidase in E. Coli is an "all-or-none" phenomenon.
TL;DR: In this article, a reformulation du probleme ergodique permet d'aborder cette question des systemes a nombre infini de degres liberte que nous allons etudier dans une publication ulterieure.
TL;DR: The role played by diffusional and convectional transport is analyzed and the single-breath test and the nitrogen wash-out are interpreted and the solution of the transport equation is obtained.
TL;DR: Alteraction of the arginine pathway regulatory gene, argR, was shown to reduce the repressibility of the enzyme by both end products while mutations affecting uridine monophosphate pyrophosphorylase (upp) besides affecting uracil uptake preclude enzyme repression by urACil or cytosine in the biosynthesis of carbamoylphosphate and the pyrimidines.
Abstract: In the course of experiments directed towards the isolation of mutants of Escherichia coli K12 with altered regulation of the synthesis of carbamoylphosphate synthetase, two types of mutations were found to affect the cumulative repression of this enzyme by arginine and uracil. Alteraction of the arginine pathway regulatory gene, argR, was shown to reduce the repressibility of the enzyme by both end products while mutations affecting uridine monophosphate pyrophosphorylase (upp) besides affecting uracil uptake preclude enzyme repression by uracil or cytosine in the biosynthesis of carbamoylphosphate and the pyrimidines. The upp mutations were located on the chromosome near the gua operon. Mutations previously designated as uraP are shown to belong to this class.