Etude de l'influence d'une microsporidiose sur les électrophorégrammes (protéinogramme et zymogramme) des protéines de l'hémolymphe deCarcinus mediterraneus (Crustacé, Brachyoure)

Summary The use of the method of concentration gradient of polyacrylamide gel, electrophoresis has permitted to reveal a difference in zymograms when studying the hemolymph of healthy crabs and that of crabs parasitized by the muscular microsporidaThelohania, maenadis., The zymograms of the parasitized crabs present an increase in chymotrypsin activity and variations in the zones of esterase activity.

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Contribution n^o 1 du Centre de Parasitologie et de Pathologie comparées de l'Université des Sciences et Techniques du Languedoc, F-34060 Montpellier Cédex.     

High molecular transport proteins for JH-III in insect hemolymph

Summary Using two independent techniques, ultracentrifugation in a KBr-gradient, and native pore polyacrylamide gel electrophoresis in combination with [³H]-epoxyfarnesyldiazoacetate photoaffinity labeling, we showed that in the hemolymph ofPeriplaneta americana, and probably also inLeptinotarsa decemlineata JH-III binds to the lipophorin, whereas inLocusta migratoria JH-III binds to a different protein.     

Zinc increases the longevity of unfertilized sea urchin eggs

Summary We have found that Zn²⁺ prevented lysis of unfertilized sea urchin eggs, and the eggs retained the ability to form fertilization membranes and to divide. SDS polyacrylamide gel electrophoresis showed that proteolysis of several proteins accompanied egg lysis, but Zn²⁺ inhibited this proteolysis. Therefore, Zn²⁺ blocks protease activity directly or indirectly and thereby prolongs the longevity of unfertilized sea urchin eggs.     

Partial purification and characterization of acid phosphatase from sporulated oocysts ofEimeria tenella

Summary Acid phosphatase ofEimeria tenella oocysts (Peak II) was purified 77-fold with a recovery of 26% using protamine sulfate precipitation, DEAE-cellulose chromatography and Sephadex G-200 gel filtration. This enzyme occurs in multiple forms as indicated by two peaks which can be separated by DEAE-cellulose chromatography and polyacrylamide gel electrophoresis. The partially purified enzyme has optimal activity at pH 4.5. With p-nitrophenyl phosphate the Km and V_max values for (Peak II) were 25 mM and 1.57 mol/min/mg protein, respectively. The enzyme (Peak II) ist strongly inhibited by Hg⁺⁺, Cu⁺⁺, iodoacetamide, fluoride and molybdate. Tartrate and other divalent metal ions have no effect on enzyme activity. The partially purified Peak II phosphatase is not a glycoprotein as it is not absorbed on concanavalin-A Sepharose and its treatment with bacterial neuraminidase does not alter its elution profile through DEAE cellulose.     

Incorporation d'acides aminés radioactifs dans les membranes des globules lipidiques du lait humain

Summary Human milk fat globule membranes (MFGM) can incorporate radioactive¹⁴C amino acids in a hot trichloracetic acid-insoluble material. Aspecific adsorption and bacterial contamination are unlikely. The products of protein synthesis were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate or by action of proteolytic enzymes. Various inhibitors of protein synthesis were assayed. Fragments of rough endoplasmic reticulum or mitochondria could be involved in this incorporation.     

Purification of the cytosol oestradiol-receptor complex from foetal guinea-pig uterus using electrofocusing on polyacrylamide plates

Summary The³H-oestradiol receptor complex obtained from the cytosol fraction of foetal guinea-pig uterus was purified by the following steps: column chromatography in Sephadex G-15 and Ultrogel, and by electrofocusing on polyacrylamide plates. In the final step a concentration of 15–17% of the foetal uterine oestradiol receptor protein was obtained. The isoelectric point (pl) of this receptor was determined to be 6.1–6.2.The expenses of the investigation were partially defrayed by a grant from the Centre National de la Recherche Scientifique (CNRS), France (Equipe de Recherche CNRS No. 187).     

Problems in the determination of isoelectric points of beta lactamases]

Analytical isoelectric focusing in polyacrylamide gels and preparative electrofocusing in density gradients may give very different pI determination for the same beta lactamase. This difference seems due to a lack of enzyme migration in some parts of the cross-linked polyacrylamide gel. This migration appears easier in density gradient isoelectricfocusing, and thus this technique yields more significant absolute pI values. Analytical isoelectric focusing should only be used for comparison studies.     

Polyacrylamide gel disc electrophoresis of rat bile after intravenous administration of52MnCl2,64CuCl2,203HgCl2, and210Pb(NO3)2

Résumé Après avoir administré i. v. à des rats les solutions des sels Pb⁺⁺, Hg⁺⁺, Mn⁺⁺ et Cu⁺⁺, on a divisé leur bile par des l'élécrophorèse de disque sur gel de polyacrylamide. Les cations Hg⁺⁺ se sont montrés surtout dans la fraction contenant des hauts polymères d'albumine spécifique pour la bile; les cations Mn⁺⁺ et Cu⁺⁺ furent observés surtout dans la zone pigmentée. Le maximum des cations Pb⁺⁺ attachés s'est trouvé dans la zone de postalbumine.     

Regulatory aspects of low intensity photon emission

Summary Photon emission from unicellular and multicellular organisms has been a subject of study for many decennia. In contrast to the well-known phenomenon of bioluminescence originating in luciferin-luciferase reactions, low intensity emission in the visible region of the electromagnetic spectrum has been found in almost every species studied so far. At present, the nomenclature of this phenomenon has not crystallized and it is referred to by a variety of names, such as mitogenetic radiation²⁹, dark luminescence⁷, low-level chemiluminescence^{20, 36}, and biophotons⁵⁷. Particular attention has been focussed on the relationship between photon emission and the regulation of various aspects of cellular metabolism, although in many cases quantitative data are still lacking. Throughout the history of this field of research the question of a functional biological role of the low intensity emission has been repeatedly raised; this is reflected, for instance, in the heterogeneity of the terms used to describe it. The discussion concerns the possible participation of photons of low intensity in intra- and intercellular communication. This paper reviews literature on the metabolic regulation of low intensity emission, as well as the regulation of photon emission initiated by external light. Furthermore, recent data are discussed with respect to a possible biocommunicative function of low intensity photon emission.     

The ontogeny ofa-foetoprotein in the chicken

Summary The ontogeny ofa-foetoprotein (AFP) has been studied in the chicken using polyacrylamide gel gradient electrophoresis and electroimmunoassay from 7 days of incubation until after hatching. The results are discussed in the light of previous on the ontogeny of AFP in mammals.     

Sectioning of polyacrylamide slab gels with a modified small animal stereotaxic instrument.

A simple and inexpensive modification of the Kopf model 900 small animal stereotaxic instrument allows it to be used temporarily as a precision polyacrylamide slab gel slicer.     

Role of p75 neurotrophin receptor in stem cell biology: more than just a marker

p75^NTR, the common receptor for both neurotrophins and proneurotrophins, has been widely studied because of its role in many tissues, including the nervous system. More recently, a close relationship between p75^NTR expression and pluripotency has been described. p75^NTR was shown to be expressed in various types of stem cells and has been used to prospectively isolate stem cells with different degrees of potency. Here, we give an overview of the current knowledge on p75^NTR in stem cells, ranging from embryonic to adult stem cells, and cancer stem cells. In an attempt to address its potential role in the control of stem cell biology, the molecular mechanisms underlying p75^NTR signaling in different models are also highlighted. p75^NTR-mediated functions include survival, apoptosis, migration, and differentiation, and depend on cell type, (pro)neurotrophin binding, interacting transmembrane co-receptors expression, intracellular adaptor molecule availability, and post-translational modifications, such as regulated proteolytic processing. It is therefore conceivable that p75^NTR can modulate cell-fate decisions through its highly ramified signaling pathways. Thus, elucidating the potential implications of p75^NTR activity as well as the underlying molecular mechanisms of p75^NTR will shed new light on the biology of both normal and cancer stem cells.     

Effect of splenectomy on the in-vitro migration inhibition response to sheep erythrocytes in the lizard,Calotes versicolor

Summary Splenectomy completely erased the PFC response to SRBC in lizards. In contrast, it has very little effect on the degree of MI to all doses ranging from 10⁴ to 10⁹, excepting the lowest dose, 10³ SRBC.Supported by PL-480 (NIH) research grant, No. 01-077.Grateful to Madurai University for the award of Studentship during the tenure of the work and to Dr P. W. Askenase for the gift of capillaries used in this study.     

Binding property of rat andLimulus C-reactive proteins (CRP) to mercury

Summary The C-reactive proteins (CRP) from both rat andLimulus were found to bind mercury (Hg) in both in vivo and in vitro conditions. CRP has high-affinity binding sites for Hg as evidenced by the loss of free sulfhydryl groups, arrested mobility in polyacrylamide gel electrophoresis, and the consumption of CRP in the serum after Hg administration. The binding was tight as it could not be inhibited either by the addition of cysteine or EDTA. By using a direct titration method it was shown that binding of Hg to CRP was saturable at a molar ratio of Hg/CRP=13.11. The possibility that CRP may act as a scavenger for Hg is discussed.     

Sectioning of polyacrylamide slab gels with a modified small animal stereotaxic instrument

Summary A simple and inexpensive modification of the Kopf model 900 small animal stereotaxic instrument allows it to be used temporarily as a precision polyacrylamide slab gel slicer.Supported by the Alfred P. Sloan Foundation.     

Prey localization by surface wave ray-tracing: Fish track bugs like oceanographers track storms

Summary Surface-feeding fish accurately determine direction and distance to the center of a concentric wave stimulus, even if only a single, short lasting wave train is presented^1,2. It has been suggested that one cue used by these fish to localize the wave center is the distance dependent frequency modulation of the initial part of a wave stimulus^3,4. Here we show how the distance information contained in the fractional frequency change of a capillary wave group can be decoded. We suggest that wave source localization in surface-feeding fish in part is based on a principal similar to that used by oceanographers to track storms by the frequency change of forerunners of swell.     

Molecular mechanisms of thrombin function

The discovery of thrombin as a Na⁺-dependent allosteric enzyme has revealed a novel strategy for regulating protease activity and specificity. The allosteric nature of this enzyme influences all its physiologically important interactions and rationalizes a large body of structural and functional information. For the first time, a coherent mechanistic framework is available for understanding how thrombin interacts with fibrinogen, thrombomodulin and protein C, and how Na⁺ binding influences the specificity sites of the enzyme. This information can be used for engineering thrombin mutants with selective specificity towards protein C and for the rational design of potent active site inhibitors. Thrombin also serves as a paradigm for allosteric proteases. Elucidation of the molecular basis of the Na⁺-dependent allosteric regulation of catalytic activity, based on the residue present at position 225, provides unprecedented insights into the function and evolution of serine proteases. This mechanism represents one of the simplest and most important structure-function correlations ever reported for enzymes in general. All vitamin K-dependent proteases and some complement factors are subject to the Na⁺-dependent regulation discovered for thrombin. Na⁺ is therefore a key factor in the activation of zymogens in the coagulation and complement systems.     

A rapid method for the purification of octopine dehydrogenase for the determination of cell metabolites

Summary Unlike other NAD⁺-dependent dehydrogenases, octopine dehydrogenase was not bound by blue Sepharose. A rapid 2-step purification procedure (gel filtration on Sephadex G-100 followed by affinity chromatography on blue Sepharose) resulted in a final preparation of octopine dehydrogenase which had a sp. act. of 65 units/mg protein and was free of contaminating NAD⁺-oxidoreductases. This preparation has been used successfully for the estimation of phospho-L-arginine, L-arginine and octopine in perchloric acid extracts.Supported by a grant from the Deutsche Forschungsgemeinschaft (Ga 241/1).     

Nicotinamide is an inhibitor of SIRT1 in vitro,but can be a stimulator in cells

Nicotinamide (NAM), a form of vitamin B₃, plays essential roles in cell physiology through facilitating NAD⁺ redox homeostasis and providing NAD⁺ as a substrate to a class of enzymes that catalyze non-redox reactions. These non-redox enzymes include the sirtuin family proteins which deacetylate target proteins while cleaving NAD⁺ to yield NAM. Since the finding that NAM exerts feedback inhibition to the sirtuin reactions, NAM has been widely used as an inhibitor in the studies where SIRT1, a key member of sirtuins, may have a role in certain cell physiology. However, once administered to cells, NAM is rapidly converted to NAD⁺ and, therefore, the cellular concentration of NAM decreases rapidly while that of NAD⁺ increases. The result would be an inhibition of SIRT1 for a limited duration, followed by an increase in the activity. This possibility raises a concern on the validity of the interpretation of the results in the studies that use NAM as a SIRT1 inhibitor. To understand better the effects of cellular administration of NAM, we reviewed published literature in which treatment with NAM was used to inhibit SIRT1 and found that the expected inhibitory effect of NAM was either unreliable or muted in many cases. In addition, studies demonstrated NAM administration stimulates SIRT1 activity and improves the functions of cells and organs. To determine if NAM administration can generate conditions in cells and tissues that are stimulatory to SIRT1, the changes in the cellular levels of NAM and NAD⁺ reported in the literature were examined and the factors that are involved in the availability of NAD⁺ to SIRT1 were evaluated. We conclude that NAM treatment can hypothetically be stimulatory to SIRT1.     

Photodynamic sensitizers assay: rapid and sensitive iodometric measurement

A rapid, sensitive and simple spectrophotometric method for the detection of¹O₂ produced by photodynamic photosensitizers in slightly acid and air-saturated aqueous solutions has been developed. The method is based on the reaction of¹O₂ (produced by photodynamic processes) with I^– in the presence of ammonium molybdate as a catalyst. The reaction product I₃ ^–, proportional to¹O₂, is followed spectrophotometrically at 355 nm. Several ways of avoiding interference with other oxidizing compounds, either present before or produced during the irradiation, are described.The method could be used to measure the efficiency of water-soluble photodynamic photosensitizers.