Crossover from spin accumulation into interface states to spin injection in the germanium conduction band.

Electrical spin injection into semiconductors paves the way for exploring new phenomena in the area of spin physics and new generations of spintronic devices. However the exact role of interface states in the spin injection mechanism from a magnetic tunnel junction into a semiconductor is still under debate. In this Letter, we demonstrate a clear transition from spin accumulation into interface states to spin injection in the conduction band of n-Ge. We observe spin signal amplification at low temperature due to spin accumulation into interface states followed by a clear transition towards spin injection in the conduction band from 200 K up to room temperature. In this regime, the spin signal is reduced to a value compatible with the spin diffusion model. More interestingly, the observation in this regime of inverse spin Hall effect in germanium generated by spin pumping and the modulation of the spin signal by a gate voltage clearly demonstrate spin accumulation in the germanium conduction band.

Transfomration of arachidonic acid into 12-hydroxy-5,8,10,14-eicosatetraenoic acid by mouse peritoneal macrophages.

Mouse peritoneal macrophages were incubated at 37 degrees C for 30 min with arachidonic acid (all-cis-5,8,11,14-eicosatetraenoic acid). Oxygenation of arachidonic acid in mouse peritoneal macrophages occurs by two major pathways: fatty acid cyclooxygenase and lipoxygenase. The major metabolite of the latter is 12-hydroxy-5,8,10,14-eicosatetraenoic acid which was identified by gas liquid chromatography on high resolution glass capillary column and mass spectrometry.

[Study of the enzymatic hydrolysis of a phosphonic ester using microcalorimetry]. / Etude de l'hydrolyse enzymatique d'un ester phosphonique par microcalorimétrie.

A "Batch" microcalorimeter is used at 30 degrees C for the study of the hydrolysis of 4-nitro-phenylphenylphosphonate with a calf-intestinal phosphonate esterase, in a tris buffer, pH 8. The yield of enzymatic hydrolysis is estimated by spectrophotometric determination of the p--nitrophenol evolved; we have then calculated the apparent molar enthalph of the reaction. (delta Happ = -72,2 kj. mol-1). Phenylphosphonic acid, the second reaction product, is not transphosphonylated on tris. The second acidity of phenylphosphonic acid was studied at 30 degrees C by sodium hydroxide electrotitration (pKa2 = 7,13) and by "Flow" microcalorimetry (delta Hionization = 19,8 kj.mol-1). In the same manner at 30 degrees C, we measured the heat of ionization of p-nitrophenol (delta Hionization = 26,75 kj.mol-1). These findings allow a calculation for the actual heat of hydrolysis of 4-nitro-phenyl-phenylphosphonate (delta Hrho = -29,7 kj.mol-1).

Human African trypanosomiasis: presence of antibodies to galactocerebrosides.

Improvements were made in the immunodetection of anti-galactocerebroside (anti-GalC) antibody in sera of patients with human African trypanosomiasis by thin-layer chromatography, enzyme-linked immunosorbent assay, and immunoadsorption. Rabbit anti-GalC antibodies were used to standardize these techniques and demonstrate their specificity. Anti-GalC antibodies were found in the sera of 42.8% of 63 patients with human African trypanosomiasis. Thirty-four control subjects living in the same endemic area were also tested. Anti-GalC levels were higher in human African trypanosomiasis patients with neurologic disturbances compared with patients without such disturbances. These antibodies were distributed mainly between the IgG and IgM classes, but 28% of the patients with human African trypanosomiasis had increased IgA levels without anti-GalC antibody activity.

Galactocerebrosides are antigens for immunoglobulins in sera of an experimental model of trypanosomiasis in sheep.

In an experimental model of human African trypanosomiasis in sheep inoculated with Trypanosoma brucei brucei, we report an immunoglobulin reactivity towards central nervous system (CNS) glycolipids. Immunocharacterization of the glycolipid antigens was performed on thin-layer chromatography using peroxidase-labelled second antibody. An immunoreactivity against galactocerebroside antigens was observed in inoculated animals up to a dilution of 1:600 and was suppressed after immunoadsorption of sera on pure galactocerebrosides. As galactocerebroside antigen is responsible for demyelination in several experimental models, the relation between the important glycolipid immunoreactivity in inoculated sheep sera and the pathogenesis of CNS demyelination in African trypanosomiasis is suggested.

Transformation of arachidonic acid into monohydroxy-eicosatetraenoic acids by mouse peritoneal macrophages.

Mouse peritoneal macrophages synthesize 6 monohydroxylated eicosatetraenoic acids when incubated with exogenous arachidonic acid. These compounds were identified by chromatographic techniques (high pressure liquid chromatography and high efficiency glass capillary column gas chromatography and mass spectrometry. The chromatographic and spectrometric data are presented. These results show that peritoneal macrophages constitute one of the best systems to study in evaluating the metabolism of oxygenated products of arachidonic acid.

[Contribution of biochemical tests in the diagnosis of the nervous phase of human African trypanosomiasis]. / Apport des examens biochimiques dans le diagnostic de la phase nerveuse de la trypanosomose humaine africaine.

The stage of human African trypanosomiasis (HAT) is important to define precisely as far as it is directly related to the type of treatment used. The beginning of the neurological involvement is difficult to find out because there is no known specific clinical or biological sign. This study is trying to look for a precise marker and has been realized in Congo. 70 subjects with parasitologically confirmed HAT and 70 controls are included. The stage of HAT is determined according to the classical definition on the field using the cerebrospinal fluid (CSF) cell count: less than 5 cells/microliters for the first stage (P1), more than 5 cells/microliters for the second stage (P2). The blood analysis has included: glucose, urea, creatinine, sodium, potassium, calcium, chloride, phosphorus, uric acid, total bilirubin, unconjugated bilirubin, total cholesterol, triglycerides, total proteins, aspartate aminotransferase, alanine aminotransferase, creatinine phosphokinase, alkaline phosphatase, gamma-glutamyltransferase, immunoglobulins M and G, C3c fraction of complement, transferrin, seromucoid alpha 1, haptoglobin and albumin. In CSF we have analyzed IgM, IgG, protein levels and the bloodbrain barrier (BBB) impairment. The comparison between the subjects and their controls, the subjects in P1 and in P2, the CSF cell count and the other CSF alterations show the interest of the IgM level in CSF and the BBB impairment to identify subjects in P2. However there is a low gradation in the biological disturbances and not a precise threshold point. Nevertheless it seems reasonable to raise the CSF cell count level to 20 cells/microliters to define the beginning of the nervous involvement.

[The detection of anti-galactocerebroside autoantibodies in human African trypanosomiasis]. / Détection d'autoanticorps anti-galactocérébrosides au cours de la trypanosomose humaine africaine.

The pathogenesis of the central nervous system (CNS) damage in human african trypanosomiasis (HAT) is unknown. In view of an immunological mechanism, as in another trypanosomiasis, Chagas' disease, the causative agent of which is Trypanosoma cruzi, we have searched autoantibodies directed against glycosphingolipids of CNS. Detection and characterization of autoantibodies were performed by ELISA and detection after thin-layer chromatography of glycolipids with sera of an experimental model of HAT in sheep and sera of patients suffering of HAT from Côte d'Ivoire and Congo. The predominant reactivity of these sera, was characterized with galactocerebrosides, the major glycolipids of the myelin. Autoantibodies were detected in 42.8% and 25% of patients' sera, respectively from Côte d'Ivoire and Congo. The proportion of these antibodies increased dramatically to 72% in sera of patients with neurological symptoms. Anti-galactocerebroside antibodies were also found in CSF of 24.4% of Congolense patients. The pathogenic significance of these anti-galactocerebroside antibodies remains to be determined. They may constitute a predicative marker for the neurological improvement in HAT.

[Circadian analysis of sleep, rectal temperature and immunological and endocrinological variables in sleeping sickness: preliminary study]. / Analyse circadienne du sommeil, de la température rectale et de variables immunologiques et endocrinologiques dans la maladie du sommeil: etude préliminaire.

A multidisciplinary study was conducted in 8 patients with neurological Human African Trypanosomiasis. The sleep-wake cycle followed an ultradian pattern which was more pronounced in patients with more severe symptoms. The EEG trace was consistently interrupted by numerous cyclic activation patterns with K complexes, rapid low amplitude elements and slow high voltage elements. Circadian rhythmicity was also disturbed in other physiological (rectal temperature), immunological (interleukins) or hormonal (cortisol, prolactin) variables, the disturbance being greater in severely hit patients.

In vitro inhibition of human lymphocyte transformation by natural or synthetic prostaglandins.

We have examined the role of 45 natural or synthetic prostaglandins (PGs) in the in vitro responsiveness of human lymphocytes toward two different varieties of mitogenic stimuli: the mixed lymphocyte culture (MLC) and the tuberculinic test (LTT). Addition of PGs to culture of lymphocytes decreases the uptake of 3H thymidin.

[DFMO: an alternative therapeutic agent for human African trypanosomiasis]. / Le DFMO: alternative thérapeutique de la trypanosomiase humaine africaine.

alpha-Difluoromethyl ornithine (DFMO) irreversibly inhibits ornithine decarboxylase (ODC), an essential enzyme for the synthesis of polyamines, and results in decreased biosynthesis of putrescine and spermidine, factors necessary for cellular multiplication. Use of this chemical agent in Trypanosoma brucei brucei infected mice eradicated the parasite from circulating blood. This treatment is now being developed for use in human pathology.

[Treatment of human African trypanosomiasis]. / Réflexions sur le traitment de la trypanosomiase humaine africanine.

The melarsoprol is still the only active drug during the nervous stage of African human trypanosomiasis, its prescription still relies on empiric rules and because of its toxicity, it appears necessary to study in gaseous phase chromatography and mass spectrometry, its pharmacokinetic in the serum and the cerebrospinal fluid (CSF) of the patients at the evolutive stage of the illness. Because of the early penetration of the Trypanosoma into the central nervous system, new therapeutic investigations should only search molecules capable to pass through the blood brain barrier: this in unfortunately not always the case, the rifamycins diffusing easily into CSF, they seem to offer a reliable way of research. For these therapeutic investigations, sheep is an easy to handle experimental model and of a reasonable cost.

Purification of lipoxygenase and hydroperoxide dehydrase in flaxseeds: interaction between these enzymatic activities.

We have purified two enzymic activities from flaxseed acetone powder: a lipoxygenase and a hydroperoxide dehydrase. The lipoxygenase activity belongs to an iron-containing protein having a molecular weight of 130 kDa which, upon incubation with alpha-linolenic acid, forms 13-hydroperoxy-9(Z), 11(E), 15(Z)- octadecatrienoic acid. The hydroperoxide dehydrase (a 55 kDa protein) metabolizes this hydroperoxide to an allene oxide which in turn is spontaneously hydrolyzed to alpha- and gamma-ketols. Relationships between these two enzymes were studied and results suggest an inhibition of the lipoxygenase by hydroperoxide dehydrase.

Quantitative profiling of the metabolic cascade of arachidonic acid by capillary gas chromatography mass spectrometry.

The analytical approach described allows for the rapid screening and concurrent quantitative determination of all of the major metabolites of the cyclooxygenase pathway of arachidonic acid, including the primary prostaglandins PGE2, PGD2 and PGF2 alpha in addition to the stable end-products of short-lived prostacyclin and thromboxane A2 (6-keto-PGF1 alpha and TXB2, respectively), generated by incubating arachidonic acid with mouse peritoneal macrophage cells. After derivatization into the corresponding methyl ester-methoxime-TMS derivative, the extracted endogenous compounds were analysed by combined high efficiency glass capillary column chromatography and selected ion monitoring. Comparatively lower detection limits can be achieved with the methyl ester-butylboronate-TMS derivatives (e.g. 10 pg for 6-keto-PGF1 alpha). A brief account is also presented on a new type of mixed methyl ester-pentafluorobenzyloxime-butylboronate-TMS derivative of TXB2 and 5-keto-PGF1 alpha.