scispace - formally typeset
Search or ask a question

Showing papers by "University of Nice Sophia Antipolis published in 1984"


Journal ArticleDOI
TL;DR: In this article, a drop calorimetric study of amorphous SiO 2, NaAlSi 3 O 8, KAlSi3 O 8, NaO 2 O 6, NaO 4 O 4, NaSiO 4 and KSiO 8 O 8 showed that the fictive temperature has negligible effect on the heat capacity above room temperature.

157 citations


Journal ArticleDOI
TL;DR: The criteria for the selection of perfluorochemicals destined to serve as oxygen carriers in second-generation blood substitutes are critically discussed and particular attention is given to the inverse excretion rate versus emulsion stability relationship and to its sharp dependence on molecular weight.
Abstract: The criteria for the selection of perfluorochemicals destined to serve as oxygen carriers in second-generation blood substitutes are critically discussed in light of the presently available body of data. The need for pure, well-defined, reproducible, industrially feasible perfluorochemicals, in order to attain the degree of reliability desirable for their use in medicine, is stressed. Particular attention is given to the inverse excretion rate versus emulsion stability relationship and to its sharp dependence on molecular weight. The range of acceptable molecular weights is established as 460–520. Oxygen-dissolving capacity, rheologic characteristics, and intravascular persistence are also discussed. The need for standard methodology and experimental protocols is reaffirmed. Perspectives are evaluated, in particular, with the aim of easing certain of the present limitations.

149 citations


Journal ArticleDOI
01 Sep 1984-Nature
TL;DR: The observations suggest that the papillomavirus E1 proteins might have a function in common with the polyoma virus large-T proteins (which are required for the initiation of viral DNA replication), which are general characteristics of eukaryotic proteins involved in the control of DNA replication.
Abstract: Nucleotide sequencing has revealed a common genetic organization for three papillomaviruses: BPV-1 (bovine papillomavirus type 1), HPV-1 (human papillomavirus type 1a) and HPV-6 (human papillomavirus type 6b). Several open reading frames, corresponding to as yet uncharacterized proteins, were observed in these genomes in the region that is required for oncogenic transformation by BPV-1 and for plasmidial maintenance of its genome. The longest of these frames, E1, is also the most conserved between the three viruses; we have compared the amino acid sequence of its putative product ('E1 protein') with those of the large-T proteins of three polyoma viruses and report here significant homologies in their carboxy-terminal halves, extending for over 200 amino acids. Moreover, similar secondary structures were predicted in this region, especially in two blocks of homologous residues, which correspond in the large-T proteins of polyoma and simian virus 40 (SV40) viruses to sites involved in the ATPase and nucleotide-binding activities. These observations suggest that the papillomavirus E1 proteins might have a function in common with the polyoma virus large-T proteins (which are required for the initiation of viral DNA replication). As it was suggested recently that the E1 gene product is involved in maintaining the BPV-1 genome as a plasmid in transformed cells, we speculate that the structural features conserved in these otherwise very different viruses are general characteristics of eukaryotic proteins involved in the control of DNA replication.

130 citations


Book ChapterDOI
TL;DR: The chapter presents a study in which the ratios of the radioactive concentrations of venous and arterial efferent liquids at isotopic equilibrium were used to determine whether, after passing over the lamellar epithelium, the perfusion liquid increased in radioactivity on passing through the venous sinus.
Abstract: Publisher Summary This chapter examines the roles of respiratory and chloride cells in branchial ion movements in teleosts. The branchial epithelium is an extremely complex tissue in both histological structure and blood circulation. In fish, the branchial and systemic circulations are in series, the heart driving the blood at a sufficiently high pressure to maintain an adequate perfusion of the entire system in spite of the flow resistance encountered in the gills. The chapter presents a study in which the ratios of the radioactive concentrations of venous and arterial efferent liquids at isotopic equilibrium were used to determine whether, after passing over the lamellar epithelium, the perfusion liquid increased in radioactivity on passing through the venous sinus. The difference between the total Na + and Cl - influxes and effluxes shows that there is a net excretion of Na + and Cl - through the seawater-adapted trout gill. In both freshwater- and seawater-adapted fish, ammonium is excreted by the lamellar epithelium. Dorsoventral arterial clearance measurements show that in both media the quantity of ammonium extracted from the blood during its passage through the lamellar epithelium is equal to the amount of NH 4+ appearing in the external medium.

100 citations


Book ChapterDOI
TL;DR: The Ca 2- -ATPase is also a membrane ATPase whose role in the cell is essential and evident, but it could also play a role in transepithelial transport and be implicated in the regulation of plasma Ca 2+ concentration.
Abstract: Publisher Summary This chapter describes the ion transport and gill ATPases in the fish gills. The gill epithelium is located between two liquid compartments of very different ionic composition. The gills are not only the site of entry for selected ions essential to life but also for the extrusion of other ions, such as HCO3-, NH3+ , and H+, which are the ionic forms of metabolic by-products. The magnitude of unidirectional fluxes, as well as the degree and direction of net fluxes, is dependent on the equilibrium established between the fish and its environment. Membranes are gently treated with ionic detergents, such as deoxycholate, dodecyl sulfate, or chaotropic agents, to release proteic constituents that are less strongly associated with phospholipids, (Na+, K+)-ATPase remaining in situ. Euryhaline species are an attractive model to compare branchial physiology from the adaptation medium and to relate physiological and biochemical aspects of ionic transport. The Ca2+-ATPase is also a membrane ATPase whose role in the cell is essential and evident, but it could also play a role in transepithelial transport and be implicated in the regulation of plasma Ca2+ concentration.

97 citations


Journal ArticleDOI
TL;DR: Saturable, high-affinity binding of iodinated toxin gamma from Tityus serrulatus scorpion venom (TiTx gamma) to Na+ channel receptor was identified in sarcolemma membrane of chick heart and reveals a single large polypeptide component of Mr230000-270000.
Abstract: Saturable, high-affinity binding of iodinated toxin γ from Tityus serrulatus scorpion venom (TiTxγ) to Na+ channel receptor was identified in sarcolemma membrane of chick heart A binding capacity of 450–600 fmol/mg of protein was found similar to that of tetrodotoxin-binding component The enrichment of these membrane-bound toxin binding sites follows that of other sarcolemma markers Kinetic data and displacement of 125I-TiTxγ from its binding sites by unlabeled TiTxγ gave an equilibrium dissociation constant (Kd) of 1–3 pM The gating component and the selectivity filter of the voltage-sensitive Na+ channel, identified as binding sites of TiTxγ and of tetrodotoxin respectively, have been efficiently solubilized with Nonidet P-40 Purification was achieved by ion-exchange chromatography on DEAE-Sephadex A-25, affinity chromatography on wheat-germ-agglutinin – Sepharose and sucrose density gradient centrifugation An enrichment of 1400-fold from the original detergent extract was measured for both toxin binding sites (1120–1230 pmol/mg of protein) Sodium dodecyl sulfate gel electrophoresis reveals a single large polypeptide component of Mr 230000–270000 The purified material exhibits an apparent sedimentation coefficient of 88 S Covalent cross-linking of 125I-TiTxγ to its membrane-embedded cardiac receptor shows that the cross-linked material, solubilized and purified by the same procedure comprises a single polypeptide chain of the same Mr of 230000–270000 Furthermore, as seen for Electrophorus electricus electroplax and rat brain, the tetrodotoxin-binding component and the TiTxγ-binding component are carried by the same polypeptide chain The functional Na+ channel might be an oligomer of this subunit of Mr 230000–270000

89 citations


Journal ArticleDOI
TL;DR: Proline endopeptidase, although it is present in synaptic membranes, is not involved in the cleavage of neurotensin at the Pro10‐Tyr11 bond, and there exists in rat brain synaptic membranes a peptidase different from proline endopesidase and endopePTidase 24.11 that is mainly responsible for inactivating neurotens in by cleaving at the pro10-Tyr 11 bond.
Abstract: UNLABELLED It was shown previously that the tridecapeptide neurotensin is inactivated by rat brain synaptic membranes and that one of the primary inactivating cleavages occurs at the Pro10-Try11 peptide bond, leading to the formation of NT1-10 and NT11-13. The present study was designed to investigate the possibility that this cleavage was catalyzed by proline endopeptidase and/or endopeptidase 24.11 (enkephalinase). Purified rat brain synaptic membranes were found to contain a N-benzyloxycarbonyl-Gly-Pro-4-methyl-coumarinyl-7-amide-hydrolyzin g activity that was markedly inhibited (93%) by the proline endopeptidase inhibitor N-benzyloxycarbonyl-Pro-Prolinal and partially blocked (25%) by an antiproline endopeptidase antiserum. In contrast, the cleavage of neurotensin at the Pro10-Tyr11 bond by synaptic membranes was not affected by N-benzyloxycarbonyl-Pro-Prolinal and the antiserum. When the conversion of NT1-10 to NT1-8 by angiotensin converting enzyme was blocked by captopril and when the processing of NT11-13 by aminopeptidase(s) was inhibited by bestatin, it was found that thiorphan, a potent endopeptidase 24.11 inhibitor, partially decreased the formation of NT1-10 and NT11-13 by synaptic membranes. IN CONCLUSION (1) proline endopeptidase, although it is present in synaptic membranes, is not involved in the cleavage of neurotensin at the Pro10-Tyr11 bond; (2) endopeptidase 24.11 only partially contributes to this cleavage; (3) there exists in rat brain synaptic membranes a peptidase different from proline endopeptidase and endopeptidase 24.11 that is mainly responsible for inactivating neurotensin by cleaving at the Pro10-Tyr11 bond.

74 citations


Journal ArticleDOI
TL;DR: The hypothesis of neurotensin receptors occurring on dopamine cell bodies and/or dendrites in human substantia nigra supporting the regulation of dopamine pathway involved in parkinsonism is supported.

71 citations


Journal ArticleDOI
TL;DR: The results indicate that nitrendipine receptors exist at the early stage of development (3-day-old-hearts) but that they do not correspond to functional slow Ca2+ channels, that in ovo development corresponds both to an increase of the number of [3H]nitrendipines receptors and to the transformation of silent Ca2+.
Abstract: The properties of interaction of the Ca2+ channel antagonist [3H]nitrendipine have been investigated in chick hearts at various stages of in ovo and post-natal development and in cultured cells. The dissociation constant of the [3H]nitrendipine-receptor complex is between 0.4 nM and 0.5 nM for intact ventricle and cultured cells. [3H]Nitrendipine binding is antagonized by nitrendipine analogs. The order of efficacy of the different dihydropyridine molecules is nitrendipine < nimodipine < nifedipine < nisoldipine with Kd values ranging from 0.5 to 4 nM. Inhibition of [3H]nitrendipine binding by other antiarrhythmic molecules like amiodarone, F13004 and bepridil was observed. Half-maximum inhibitions (K0.5) were found for verapamil and D600 at concentrations between 0.23 and 0.26 μM. The potency of organic Ca2+ blockers to depress by 50% the maximum amplitude of spontaneous beating of heart cells is closely related to K0.5 values obtained from [3H]nitrendipine binding experiments. Electrophysiological results indicate that the slow channel is insensitive to nitrendipine at the younger stage of development (3-day-old) whereas, in adult like cells, nitrendipine (50 nM) abolished both slow action potential due to the slow Ca2+ channel and contraction. The maximum binding capacity for [3H]nitrendipine is found to increase during development of the embryonic heart from 40 fmol/mg protein at day 3 to 100 fmol/mg protein at day 14, to stay relatively stable until day 18. Then the number of sites increases rapidly to reach a second plateau at 210 fmol/mg protein on day 4 after hatching. Treatment with 6-hydroxydopamine results in 35% increase in [3H]nitrendipine binding, whereas reserpine treatment is without effect. Developmental properties of nitrendipine-sensitive Ca2+ channels have been compared with those of tetrodotoxin-sensitive Na+ channels and muscarinic receptors. These results indicate that nitrendipine receptors exist at the early stage of development (3-day-old-hearts) but that they do not correspond to functional slow Ca2+ channels, that in ovo development corresponds both to an increase of the number of [3H]nitrendipine receptors and to the transformation of silent Ca2+ channels into functional Ca2+ channels, and that there is a regulation of the level nitrendipine-sensitive Ca2+ channels by innervation.

60 citations


Journal ArticleDOI
TL;DR: The binding of monoiodo [125I-Tyr3]-neurotensin to human brain was characterized and visualized using radioreceptorassay and autoradiographic techniques and demonstrated the crucial role of the C-terminal hexapeptide portion of neurotensin for binding to its receptors.

59 citations


Journal ArticleDOI
TL;DR: The nitrendipine receptor associated with the voltage-dependent calcium channel from rabbit skeletal muscle transverse tubule membranes has been solubilized by detergent extraction and it was concluded that these different binding sites are tightly coupled.
Abstract: The nitrendipine receptor associated with the voltage-dependent calcium channel from rabbit skeletal muscle transverse tubule membranes has been solubilized by detergent extraction. A highly stable solubilized receptor preparation was obtained using 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulfonate as detergent with phospholipids or glycerol present as stabilizing agents. Binding of [3H]nitrendipine to the solubilized receptor was reversible and saturable. At 4°C the equilibrium dissociation constant of the [3H]nitrendipine receptor complex was 7±3nM and was close to that determined from the rate constants of association (k1= 1.3 105 M−1 s−1) and dissociation (k−1= 1.10 × 10−3 s−1) of 8.4nM. The nitrendipine concentration that gave a half-maximal inhibition of [3H]nitrendipine binding to the solubilized receptor was 10 nM, which was similar to the values for the dissociation constant determined for the radiolabelled ligand. [3H]Nitrendipine binding to its solubilized receptor was also inhibited by other antiarrythmic drugs, such as bepridil and verapamil, and enhanced by d-cis-diltiazem. Since these drugs are apparent non-competitive inhibitors of [3H]nitrendipine binding it was concluded that these different binding sites are tightly coupled. Sucrose density sedimentation of solubilized nitrendipine receptor resulted in the separation of three [3H]nitrendipine binding activities with apparent sedimentation coefficients of 11.4 S. 14.4 S and 21S.

Journal ArticleDOI
TL;DR: In this paper, the Hopf bifurcation theorem is applied to prove the existence of limit cycles in certain difference equations occurring in biomathematics (hypercycle, two loci-two alleles) and also extended to general Runge-Kutta methods.
Abstract: If an ordinary differential equation is discretizised near an asymptotically stable stationary solution with a pair of imaginary eigenvalues by Euler's method with constant step lengthh, small invariant attracting cycles of radiusO(h1/2) will appear This Hopf bifurcation theorem is applied to prove the existence of limit cycles in certain difference equations occurring in biomathematics (hypercycle, two loci-two alleles) and is also extended to general Runge—Kutta methods

Journal ArticleDOI
TL;DR: The results suggest that the Ca2+-dependent K+ channel from rat cortex is an oligomeric structure of Mr containing an apamin-binding subunit of Mr = 33 000 +/- 2000, which is similar to those found for the membrane-bound apamin receptor.
Abstract: Radiation-inactivation was used to assess the functional size of the apamin-binding component of the Ca2+-dependent K+ channel The amount of specific binding of 125I-apamin to receptors in synaptic membranes of rat cortex decayed exponentially with increasing doses of ionizing radiation and target size analysis was consistent with a relative molecular mass of 250000 ± 20000 for the 125I-apamin receptor Analysis on sodium dodecyl sulfate gels following covalent cross-linking of 125I-apamin to its receptor in a synaptosomal membrane preparation from rat cortex revealed a single labelled polypeptide chain ofMr= 33000 ± 2000 in the presence of protease inhibitors Our results suggest that the Ca2+-dependent K+ channel from rat cortex is an oligomeric structure of Mr= 250000 ± 20000 containing an apamin-binding subunit of Mr= 33000 ± 2000 The apamin-binding component of the Ca2+-dependent K+ channel from rat synaptosomes was solubilized using detergents such as sodium cholate or 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate Phospholipids did not increase the stability of the apamin-binding component during the solubilization Binding of apamin to its solubilized receptor is reversible and saturable The dissociation constant of the apamin-receptor complex is 40–150 pM the rates constants of association and dissociation being 32 × 106 M−1 s−1 and 14 × 10−4 s−1 respectively These binding characteristics are similar to those found for the membrane-bound apamin receptor

Journal ArticleDOI
TL;DR: Amitriptyline prevented the secretion of histamine in response to stimulation by neurotensin, substance P, somatostatin or compound 48/80 but was without effect on the secretionof endogenous 5‐HT.
Abstract: The peptides, neurotensin, substance P, somatostatin, and bombesin, several analogues and fragments of neurotensin and compound 48/80, all caused the secretion of both endogenous 5-hydroxytryptamine (5-HT) and histamine. There was no differential effect of any of the secretagogues tested on the secretion of 5-HT and histamine. Amitriptyline prevented the secretion of histamine in response to stimulation by neurotensin, substance P, somatostatin or compound 48/80 but was without effect on the secretion of endogenous 5-HT.

Journal ArticleDOI
TL;DR: Ob17 cells grown and maintained in serum-free hormone-supplemented medium retain the ability to convert to adiposelike cells after serum addition, and cannot be substituted by the addition of growth hormone or of other putative adipogenic factors, or both.
Abstract: Ob17 is a clonal cell line isolated from the epididymal fat pad of C57 BL/6J ob/ob mouse that differentiates into adiposelike cells in serum-supplemented medium. In serum-free medium, this cell line shows increased growth under the addition of insulin, transferrin, fibroblast growth factor (FGF), and a factor present in extract of rat submaxillary gland (SMGE). This medium is referred to as 4F. Epidermal growth factor or nerve growth factor cannot replace SMGE, whereas partially purified platelet extract can substitute for FGF but only partially for SMGE. 4F Medium is able to support the proliferation of cells from other established preadipocyte clonal lines, HGFu and 3T3-F442A, and also of preadipocyte cells isolated from the stromal-vascular fraction of rat and mouse adipose tissues. In each case 4F medium is insufficient to support the differentiation of these cells into adipocytes. Ob17 cells grown and maintained in serum-free hormone-supplemented medium retain the ability to convert to adiposelike cells after serum addition. This serum requirement for differentiation cannot be substituted by the addition of growth hormone or of other putative adipogenic factors, or both. The results are discussed with respect to the requirements for growth and differentiation of the 3T3-L1 and 1246 preadipocyte cell lines previously described.

Journal ArticleDOI
TL;DR: The results show that insulin is neither required for the commitment of stem cells to preadipocytes nor for the onset of the differentiation program and the post-confluent mitoses of preadendipocytes to adipocyte-like cells.

Journal ArticleDOI
TL;DR: The relationship between the establishment of the Na+-dependent valine uptake and the ionic events triggered by fertilization is discussed and has characteristics in common, such as their insensitivity to metabolic energy supply, their energy of activation and their ability to concentrate valine.

Journal ArticleDOI
TL;DR: Na+ channels, which are known to be located mainly at the nodes of Ranvier in normal myelinated axons, are increased in number in +med/+med mice even before the disease becomes clinically established.

Journal ArticleDOI
TL;DR: The isolated, saline-perfused head of the freshwater rainbow trout was used to investigate adrenergic control of branchial chloride transport and it is possible to postulate a scheme for piscine acid-base regulation involving altered rates of Cl−/HCO3− and Na+/H+ (NH4+) exchanges, both a result of adrenergic stimulation.
Abstract: 1. The isolated, saline-perfused head of the freshwater rainbow trout (Salmo gairdneri) was used to investigate adrenergic control of branchial chloride transport. 2. Perfusing only with physiological saline (no catecholamines present) resulted in extremely low values of chloride influx (J iCl−) which approached zero with time. 3. By perfusing with a range of sympathetomimetics and adrenergic antagonists, it was demonstrated that branchial chloride influx was enhanced by alpha receptor stimulation and inhibited by beta receptor stimulation. 4. It is proposed that the effects of catecholamines onJ iCl− are specific in nature and not due to accompanying haemodynamic alterations. 5. From the results of these experiments, together with previous knowledge of adrenergic effects on branchial Na+/H+ (NH 4 + ) exchange, it is possible to postulate a scheme for piscine acid-base regulation involving altered rates of Cl−/HCO 3 − and Na+/H+ (NH 4 + ) exchanges, both a result of adrenergic stimulation.

Book ChapterDOI
TL;DR: The selective increase in the permeability of small lipophilic molecules under adrenaline action in freshwater-adapted fish indicates an effect of the catecholamine on the lipid mobility of the plasmalemma.
Abstract: Publisher Summary This chapter examines the water and nonelectrolyte permeation in the fish gill The study of nonelectrolyte gill exchanges is important because it permits the elucidation of various phenomena The fish gill can be considered as the sum of two epithelia: the respiratory and nonrespiratory The comparison of branchial morphology of fishes adapted to fresh water or seawater pointed out structural modifications of two pathways: the membranes of chloride cells, which represent the exchange surface of the nonrespiratory epithelium (4% of the total area) and, (c) the intercellular junctions The number of chloride cells increases in seawater by a factor of about three and loose junctions, permeable to lanthanum ions, appear among chloride cells on the apical side The selective increase in the permeability of small lipophilic molecules under adrenaline action in freshwater-adapted fish indicates an effect of the catecholamine on the lipid mobility of the plasmalemma An intermediate compartment, probably consisting of intracellular water, exists for water exchange Two barriers exist that water molecules must successfully pass to cross the epithelium: external and internal membranes The basal barrier is about eight times less permeable, and thus is the limiting factor for water diffusion, as well as ionic exchanges in the gills


Journal ArticleDOI
TL;DR: The authors' analysis of nucleotide sequences at the junction between simian virus 40 (SV40) and cellular DNA in the Fisher rat transformed line tsA30-N2 demonstrates that in both cases, recombination preferentially takes place near short direct repeats in the virus genome.

Journal ArticleDOI
TL;DR: The importance of zooplankton communities is emphasized, and the necessity of elucidating the temporal and spatial migrations and exchanges between reef and planktonic organisms in order to gain more insight into their trophic relationship with the reef system is emphasized.
Abstract: Diurnal and nocturnal zooplankton was sampled simultaneously at the surface and at 35 m depth on the outer slope of the fringing reef off the Jordanian coast in the Guff of Aqaba, Red Sea, over a period of 8 d during July 1982. Complementary surface sampling was carried out above the reef and in the open sea in the morning and afternoon for a period of 5 d. Five groups of organisms were classified according to changes in their vertical distribution in the water column which is analyzed and discussed. Zooplankters of the first group appear to be positively phototactic (Calanus robustior, Mecynocera clausi, Oithona helgolandica, Corycella rostrata). Those of the second group also seem to be positively phototactic, but only as regards average and low light (moonlight) intensities (Nannocalanus minor, Acartia negligens, Sagitta enflata, S. hexaptera, Thalia democratica, Oikopleura fusiformis, O. longicauda). The zooplankton of the third group displays a negative phototaxis (Oithona nana, calyptopis and furcilia euphausiid stages, pelecypods and other mollusc veligers). Species exhibiting uncertain behaviour or caught in low numbers and exhibiting no particular distribution are relegated to the fourth and the fifth groups. The horizontal microdistribution of the zooplankton community is not easily discernible: certain neritic or oceanic affinities can be identified, however, by comparing the WP2 standard net surface samples collected above the reef with those from the open sea. The importance of zooplankton communities is emphasized, and the necessity of elucidating the temporal and spatial migrations and exchanges between reef and planktonic organisms in order to gain more insight into their trophic relationship with the reef system.

Journal ArticleDOI
TL;DR: In this paper, a SEABEAM survey of the East Pacific Rise (EPR) led to the selection of several sites having structural characteristics favorable for hydrothermal activity.

Journal ArticleDOI
TL;DR: In this paper, the reaction of F-alkyl oxirans to nucleophilic and electrophilic reagents was investigated and it was shown that they are quite inert in acid medium.


Journal ArticleDOI
TL;DR: In this article, drop calorimetry measurements for four Na20-Si02 liquids indicate that, to within ± 0.5%, the heat capacities are temperature-independent between 900 and 1800 K and additive functions of composition for liquids containing from 50 to 100 mol% Si02.
Abstract: Drop calorimetry measurements for four Na20-Si02 liquids indicate that, to within ±0.5%, the heat capacities are temperature-independent between 900 and 1800 K and additive functions of composition for liquids containing from 50 to 100 mol% Si02. In this composition interval, the partial molar heat capacities of Si02 and Na20 are 81.37 and 100.6 J /mole-K, respectively.

Journal ArticleDOI
TL;DR: The results strongly suggest that the plasma membrane of unfertilized eggs contains a preexisting Na+‐K+ transporting system which is obligatorily stimulated at fertilization.
Abstract: Biochemical and kinetic characteristics of the Na+-K+ exchange were studied in Paracentrotus lividus eggs. Measurement of the 86Rb uptake shows that ouabain-sensitive 86Rb uptake is dramatically stimulated within the first minute following fertilization. The Na+-K+ pump-mediated K+ entry presents a maximal rate at 8 min postfertilization and then decreases to reach a plateau within 30 min. We assess that the steep rise in cell K+ occurring at fertilization (J.P. Girard, P. Payan, C. Sardet, Exp. Cell. Res. 142:215-221, 1982) does not originate from a net entry of external K+. Measured 30 min postfertilization, the half-maximal activation by K+ of the ouabain-sensitive Na+-K+ exchange is 5-6 mM and the ouabain IC50 is 5.10(-5) M. Egg cortices from unfertilized and fertilized eggs show comparable Na+-K+ ATPase activity with a 50% ouabain-sensitive fraction. Vm and Km for Na+ and K+ of the enzyme are of the same order of magnitude in cortices of unfertilized and fertilized eggs. Cortical Na+-K+ ATPase from unfertilized eggs shows a ten fold increase of activity between pH 6.7 and pH 7.7. The results strongly suggest that the plasma membrane of unfertilized eggs contains a preexisting Na+-K+ transporting system which is obligatorily stimulated at fertilization.

Journal ArticleDOI
01 Nov 1984-Placenta
TL;DR: The identification of the distribution of antigens in common with ectodermal tissues and extra-embryonic membranes suggests that human amnion and chorion may have a close embryological relationship with embryonic ectoderm and its subsequent products of organogenesis.