Showing papers by "University of Geneva published in 1969"
TL;DR: The authors of this study examine the question of whether the so-called enterochromaffin or argentaffin cells of the gastrointestinal tract should be considered as a single cell type, and their appearance corresponds to that of pancreatic D cells.
Abstract: The authors of this study examine the question of whether the so-called enterochromaffin or argentaffin cells of the gastrointestinal tract should be considered as a single cell type. The systematic application of purely morphologic methods has led to the conclusion that the epithelium of the gastrointestinal mucosa comprises endocrine cells of several types. This conclusion is primarily based on the uneven and characteristic distribution of the various cell types along the intestinal tract, an observation precluding the interpretation that the different types correspond to diverse functional stages of the same cell. A specific endocrine function may be attributed to each of the given cell types recognized so far on account of their appearance and their localization in characteristic areas of the gastrointestinal tract. It is acknowledged, however, that a purely morphological study leaves room for doubt. The first cell type is probably responsible for the formation of 5-hydroxytryptamine. Cells of type II are morphologically comparable to the pancreatic A cells and may, therefore, be called intestinal A cells. Cell type III comprises intestinal D cells since their appearance corresponds to that of pancreatic D cells. Cell type IV might well be responsible for catecholamine production, whereas gastrin is in all probability produced in endocrine cell type V. As yet, the thorough morphological study of the gastrointestinal epithelium does not provide information as to additional distinct cellular sites of production of the several other hormones isolated from different parts of the gut.
253 citations
TL;DR: The study deals in particular with the frequency, the clinical variability, the mode of inheritance, the evolution and the nosological position of the B-B syndrome, as compared with that of the simple pigmentary retinopathias.
240 citations
TL;DR: Previous evidence of a close identity between the actions of GABA and of the normal transmitter of cortical IPSPs is greatly reinforced, probably owing to a large influx of Cl−.
Abstract: 1.
In cats under Dial, multiple micro-electrodes were used to analyze the changes in membrane potential and conductance of cortical neurones produced by inhibition (evoked by surface shocks) and by microiontophoretic applications of GABA.
2.
IPSPs are associated with a marked but variable increase in membrane conductance. At the peak, the conductance may rise 3–4 fold. 52 estimates gave a mean increase of 54.0% (S.D. 77%).
3.
The time course of the main increase in conductance coincides approximately with the time course of the IPSP and the period of reduced excitability. After an initial phase of very high conductance, the conductance diminishes exponentially with a time constant of about 50 msec.
4.
GABA causes a very striking increase in membrane conductance and, in most cases, a negative shift in membrane potential.
5.
Estimates of the reversal potential of the action of GABA (EGAB) agree well with estimates of the reversal potential for IPSPs (EI) obtained before or after the application of GABA. There was a strong positive correlation between values of EI and EGAB, and the slope of the line describing EI vs EGAB, did not differ significantly from 1.0
6.
These observations therefore greatly reinforce previous evidence of a close identity between the actions of GABA and of the normal transmitter of cortical IPSPs.
7.
The increase in conductance produced by GABA shows an initial peak (mean 17.1 n-mho/nA GABA current, S.E. 4.50, n=41) and then tends to fall, after 10–20 sec, to a relatively stable level (mean 9.31 n-mho/nA (S.E. 2.38, n=32)). This phenomenon is particularly evident with large doses of GABA.
8.
A maintained application of GABA is usually associated with a change in EI towards greater positivity, probably owing to a large influx of Cl−.
203 citations
TL;DR: The nucleotide sequence of the 5′ end of bacteriophage Qβ RNA has been determined by a new method involving partial synthesis of the RNA in vitro and a very stable hydrogen-bonded loop seems to exist close to the 5″ end of the molecule.
Abstract: The nucleotide sequence of the 5′ end of bacteriophage Qβ RNA has been determined by a new method involving partial synthesis of the RNA in vitro. Neither of the codons commonly associated with the initiation of protein synthesis (AUG and GUG) was found before position 62. The sequence required for the initiation of synthesis of the coat protein (PuUGGCN) is not within the first 300 nucleotides from the 5′ end. A very stable hydrogen-bonded loop seems to exist close to the 5′ end of the molecule.
133 citations
TL;DR: Electrotonic coupling was found between heterotypic cells (myoblasts and fibroblasts), and typical nexuses were found at myoblast–myoblast junctions but not at fibroblast–fibroblast and myOBlast–f Bibroblast junctions, suggesting that electrotonics may occur through junctional structures other than the nexus.
Abstract: Publisher Summary This chapter describes a method for preparing practically pure cultures of cardiac myoblasts and fibroblasts. By using this technique, the properties of three functionally distinct types of cell junctions and the effects of association of heterotypic cells can be determined. In a study described in the chapter, the attenuation length of mixed cultures was intermediate between the two extremes. Electrotonic coupling was found between heterotypic cells (myoblasts and fibroblasts). The measured membrane potential of fibroblasts was higher when they were in intimate association with myoblasts in mixed cultures than in pure cultures. Conversely, the resting potential of stray myoblast contaminants in predominantly fibroblastic cultures was of the same magnitude as that of the surrounding fibroblasts. Neither myoblast–myoblast junctions nor fibroblast–fibroblast junctions exhibited rectification. Typical nexuses were found at myoblast–myoblast junctions but not at fibroblast–fibroblast and myoblast–fibroblast junctions. This suggests that electrotonic coupling may occur through junctional structures other than the nexus.
128 citations
TL;DR: The implication of the endoplasmic reticulum and the Golgi apparatus in the secretory cycle of the gastrin-producing cells in the cat is discussed on the basis of the ultrastructural findings.
Abstract: The gastrin-producing cells in the cat have been studied under various experimental conditions indicating the secretory cycle of these cells. Normal gastrin cells in animals fed ad libitum show secretory granules of different electron density. After fasting for 24 hrs the cells are granulated with electron dense secretory granules and after refeeding the cells are degranulated, showing clear secretory granules. The implication of the endoplasmic reticulum and the Golgi apparatus in the secretory cycle is discussed on the basis of the ultrastructural findings.
124 citations
TL;DR: An attempt was made to interpret the receptor and spike potentials in terms of passive movements of Na and K across the membrane of the retinula cell in a solution in which all the Na had been replaced by choline, Tris, or sucrose.
Abstract: The influence of changes in the ionic composition of the bathing medium on responses of the retinula cell of the honeybee drone to light was examined by means of intracellular microelectrodes. The resting potential of the cell was influenced mainly by the concentration of K. The peak of the receptor potential (the transient), which in a normal solution and with strong light approaches zero membrane potential, overshot this level in a K-rich solution. An increase in the concentration of K also raised the level of the steady-state phase of the receptor potential (the plateau). The amplitude of the receptor potential was decreased and the spike potential rapidly abolished when Na was replaced by either sucrose, choline, or Tris. In a Ca-free solution the amplitude of the response and especially that of the plateau, was increased. An increase in Ca had the opposite effects. All these changes were reversible. An attempt was made to interpret the receptor and spike potentials in terms of passive movements of Na and K across the membrane of the retinula cell. The major difficulty encountered was to find an explanation for the persistence of an appreciable fraction of the transient and the plateau in preparations kept up to 12 hr in a solution in which all the Na had been replaced by choline, Tris, or sucrose.
114 citations
107 citations
TL;DR: Results were interpreted as consistent with the hypothesis that insulin release from this preparation is dependent, at least in part, upon activation of the adnyl cyclase syste.
84 citations
TL;DR: In this article, a Reggeized resonance model for a scalar $n$-point function is given in the form of an integral, and a multiple factorization theorem is proved.
Abstract: A Reggeized resonance model for a scalar $n$-point function is given in the form of an integral. Reggeization and a multiple-factorization theorem is proved. Feynman rules are developed for the parent resonance couplings and compared with the Regge results. An approximation scheme for simplifying the $n$-point function is suggested, and based on this approximation scheme, a Bethe-Salpeter-type equation is derived for the multiperipheral processes.
79 citations
TL;DR: It is suggested that insulin release from this preparation is an energy-dependent process, which requires the intracellular accumulation of both 3′,5′-cyclic AMP and of product, or products, of the intermediary metabolism of glucose and/or pyruvate.
TL;DR: An electron microscope study of the various stages of erythropoiesis and erythrophagocytosis suggests the possibility that the various patterns of interaction of macrophages with erythroblasts, immature and mature ery throatcytes, are due to variations in the zeta potentials of the blood cells.
Abstract: The observation of macrophages which can act either as scavenger cells or as nurse cells leads to the conclusion that the factors responsible for the release of young erythrocytes or for the destruction of old erythrocytes lie with the red blood cells themselves rather than with the macrophages.
TL;DR: It is proposed that the recognition of a natural termination signal involves a sequence longer than a nonsense codon and that nonsense codons outside of their natural environment induce variable termination rates which are reflected in the suppression potential.
Abstract: We have examined the response of phage T4 nonsense mutations located at various sites within the same cistron to different suppression agents. A wide range of suppression efficiency is found for both ochre (UAA) and amber (UAG) mutations under conditions where suppression provides a measurement of the amount of chain propagation past the mutated site. We have established a relationship between our measurement-the size of the phage yield-and the amount of rIIB product present in the infection. Our data suggest that the 1000-fold range of variations in yields observed in the rIIB cistron corresponds to a 30-fold range of variation in the level of rIIB product, i.e. in the relative frequency of chain propagation past the various nonsense codons included in our test. From the parallelism of response of any particular mutant to very different suppression mechanisms we conclude that the efficiency of suppression is site specific, that is to say, that the main factor determining the frequency of chain propagation at a nonsense codon by any type of suppression mechanism is the nucleotide sequence adjacent to the nonsense codon (reading context). We propose that the recognition of a natural termination signal involves a sequence longer than a nonsense codon and that nonsense codons outside of their natural environment induce variable termination rates which are reflected in the suppression potential.
TL;DR: It can be concluded that the most important step in determining the selectivity of transcription is initiation, and the mechanism of RNA polymerase action in terms of the regulation of RNA synthesis is discussed.
Abstract: Publisher Summary This chapter discusses the mechanism of RNA polymerase action in terms of the regulation of RNA synthesis. The evidence presented indicates that accurate and selective transcription of DNA can be achieved with very pure RNA polymerase. It can be concluded that the most important step in determining the selectivity of transcription is initiation. The most important aspect of the regulation of gene activity is the absolute control of transcription. The regions under positive control, such as the late genes, depend on the presence of some additional protein factor to be transcribed at all. Regions that are subject to negative control, such as the lactose operon in E. coli, are restricted in the initiation of mRNA synthesis. The lactose repressor is known to bind to a region of DNA just adjacent to the region where transcription of the lactose operon is presumably initiated. Therefore, the action of this repressor is to prevent initiation of transcription at the site to which it binds.
TL;DR: The data suggest that this glyoxysome-like organelle carries part, if not all, of the constitutive isocitrate lyase, which seems to appear in a soluble form which subsequently might become attached to the particle.
TL;DR: The sequence of in vitro transcription of T4 DNA seems to parallel the in vivo process, and the results are consistent with the findings of previous studies on T4 knockout mice and T3 knockout mice.
Abstract: The sequence of in vitro transcription of T4 DNA seems to parallel the in vivo process.
TL;DR: The contribution of fourth-order vacuum polarization to sixth-order radiative correction to the electron magnetic moment is analytically evaluated and found to be 0,055(α/π)3 as mentioned in this paper.
Abstract: The contribution of fourth-order vacuum polarization to sixth-order radiative correction to the electron magnetic moment is analytically evaluated and found to be 0,055(α/π)3.
TL;DR: Dans deux notes publiees en 1964 and 1965, Vakaet conclut que la partie anterieure de la jeune ligne primitive, transplantee a la peripherie de l9aire pellucide, ne peut induire que le cerveau, tandis that son segment moyen induit exclusivement the formation d9une nouvelle ligne basic.
Abstract: Dans deux notes publiees en 1964 et 1965, Vakaet conclut que la partie anterieure de la jeune ligne primitive, transplantee a la peripherie de l9aire pellucide, ne peut induire que le cerveau, tandis que son segment moyen induit exclusivement la formation d9une nouvelle ligne primitive. Pourtant, Gallera (1968) a obtenu, dans quelques cas, l9induction d9un cerveau par le segment moyen de la jeune ligne primitive, si bien que la regie etablie par Vakaet n9a pas une valeur aussi absolue qu9il le pense. Nous avons repris ces experiences systematiquement d9une part pour verifier si la potentialite d9induire le cerveau et celle de provoquer la formation d9un nouveau centre gastruleen sont aussi strictement localisees que l9affirme Vakaet et d9autre part pour voir si la nature de la reponse de l9ectoblaste de l9hote ne depend pas en partie de son âge, et, enfin, pour etablir le role joue dans le processus d9induction par l9endoblaste presomptif contenu dans la ligne primitive.
TL;DR: The purpose was to determine whether there are grounds to believe that the flow of current responsible for depolarization of the retinula cell passes through the membrane of the microvilli.
Abstract: In the retinula cell of the honeybee drone, the response to light, recorded with intracellular micoelectrodes, consists of a graded depolarization. This potential change is probably caused by an increase in membrane permeability and by an ionic current flowing from the extracellular space into the retinula cell (1). In the drone, eight retinula cells are grouped together to form an ommatidium. The center of the ommatidium is occupied by the rhabdome, a compact arrangement of microvilli formed by the retinula cells (2). The rhabdome is thought to contain the photo pigment and, therefore, to initiate the response to light (3). In studying the distribution of diffusion tracers within the ommatidium, our purpose was to determine whether there are grounds to believe that the flow of current responsible for depolarization of the retinula cell passes through the membrane of the microvilli. The possibility that this was the case has been denied by a number of authors (4, 5), who have pointed out the compact arrangement of the microvilli and the presence of desmosomes around the rhabdome.
TL;DR: A 60 per cent fragment of R 17 RNA from the 3′ terminated end contains a binding site which specifically binds one molecule of R17 coat protein which may be the binding site involved in the inhibition of translation of the RNA synthetase cistron by coat protein.
Abstract: A 60 per cent fragment of R17 RNA from the 3′ terminated end contains a binding site which specifically binds one molecule of R17 coat protein. This may be the binding site involved in the inhibition of translation of the RNA synthetase cistron by coat protein.
TL;DR: This perfusion technique is also recommended for study when exact timing is necessary, for example in autoradiography, and is good tissue preservation.
Abstract: A method permitting exact time studies in diffusion tracer experiments in vivo is described. The method consist in application of perfusion fixation via the aorta abdominalis after the injection of the tracer substance. As the animal can be prepared for perfusion before the tracer is injected, time accuracy is in the order of a few seconds. Some applications of the method are demonstrated. A further advantage of the method is good tissue preservation. This perfusion technique is also recommended for study when exact timing is necessary, for example in autoradiography.
TL;DR: It is suggested that the intracellular concentration of free fatty acids, possibly that of ATP, may explain the action of these different hormones upon the uptake of α-aminoisobutyric acid by the fat cells, although an additional direct effect upon the transport mechaism per se cannot be excluded.
TL;DR: A study of the effect of intracellular Na suggests that the simultaneous presence of 3–4 Na ions is necessary for activating the internal site of the pump, and a half-maximal activation of the Na-K-pump with 3.8 mM K is found.
Abstract: 1.
The ionic content of nerve fibres in the rabbit's cervical vagus was measured by flame photometry. Immediately after dissection the intracellular K was 98.0±4.0 and the Na 42.0±2.5 mM/l. Incubation for 5 hr in Locke produced little change in these values.
2.
In K-free Locke the fibres lost K and gained Na. The loss of K had a rate constant of 0.0142 min−1, corresponding to an efflux of 0.313 p-mole/cm2·sec. Lowering the pH from 7 to 6 did not affect the efflux of K.
3.
The K and Na contents were restored to the initial values within 30 min after addition of 5.6 mM K to the K-free solution. The restoration was inhibited by ouabain.
4.
The rate of increase in intracellular K produced by different extracellular concentrations of K indicated a half-maximal activation of the Na-K-pump with 3.8 mM K.
5.
Lowering the pH from 7 to 6 increased the half-maximal activation constant to 13.3 mM K, suggesting inhibition of the pump by H+.
6.
A study of the effect of intracellular Na suggests that the simultaneous presence of 3–4 Na ions is necessary for activating the internal site of the pump. Half-maximal activation was found with an intracellular Na content of 29.5 mM.
7.
Li ions showed a slight activating effect at the external site; their activating effect on the inside was at least 43–44 times smaller than the effect of Na.
TL;DR: In this article, Veneziano's model was generalized to the five-point function and the coupling constants of exchanged resonances were deduced for the processes K K → 3π and K K to K K π, and the results are partial SU(3), ωφ and ff′ mixing angles.
TL;DR: Estimates indicate that proinsulin is released from rat pancreas during constant glucose stimulation in vitro, and release was detectable within 30-40 minutes of stimulation.
TL;DR: A carrier system forming a ternary complex with glucose and K+ and/or Na+ is postulated, and both K+ lack and the presence of ouabain increased glucose uptake and metabolism and were reversible.
TL;DR: In this article, le spin du noyau relaxe via an excitation virtuelle des impuretes magnetiques, auxquelles il est couple par l'interaction de Yosida.
TL;DR: Plasma concentrations of human growth hormone were measured after acute administration of corticotrophin and insulin to normal subjects and it seems that corticOTrophin may be a physiological mediator of stress-induced H.G.H. release.
TL;DR: Preliminary findings of the effect of AMS on macrophages of mice and on antibody synthesis induced with sheep red blood cells (SRBC) and diphtheria toxoid (DT) are reported.
Abstract: PASSAGE through macrophages is necessary if certain antigens are to be immuriogenic1–7, which suggests that anti-macrophage serum (AMS) may interfere with immunological response as does anti-lymphocyte serum. In mice treated with AMS, however, antibody synthesis is not inhibited8,9. This article reports preliminary findings of the effect of AMS on macrophages of mice and on antibody synthesis induced with sheep red blood cells (SRBC) and diphtheria toxoid (DT).
TL;DR: In this article, the ternary system Nb 3 Au x Pt 1−x shows a maximum of the transition temperature T c for an intermediate concentration, and the influence of annealing conditions on T c was studied.