A2Sign: Agnostic Algorithms for Signatures-a universal method for identifying molecular signatures from transcriptomic datasets prior to cell-type deconvolution

MOTIVATION

Molecular signatures are critical for inferring the proportions of cell types from bulk transcriptomics data. However, the identification of these signatures is based on a methodology that relies on prior biological knowledge of the cell types being studied. When working with less known biological material, a data-driven approach is required to uncover the underlying classes and generate ad hoc signatures from healthy or pathogenic tissue.

RESULTS

We present a new approach, A2Sign: Agnostic Algorithms for Signatures, based on a non-negative tensor factorization (NTF) strategy that allows us to identify cell-type-specific molecular signatures, greatly reduce collinearities and also account for inter-individual variability. We propose a global framework that can be applied to uncover molecular signatures for cell-type deconvolution in arbitrary tissues using bulk transcriptome data. We also present two new molecular signatures for deconvolution of up to 16 immune cell types using microarray or RNA-seq data.

AVAILABILITY AND IMPLEMENTATION

All steps of our analysis were implemented in annotated Python notebooks (https://github.com/paulfogel/A2SIGN). To perform NTF, we used the NMTF package, which can be downloaded using Python pip install.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

A 3D Human Liver Model of Nonalcoholic Steatohepatitis

Background and Aims: To better understand nonalcoholic steatohepatitis (NASH) disease progression and to evaluate drug targets and compound activity, we undertook the development of an in vitro 3D model to mimic liver architecture and the NASH environment. Methods: We have developed an in vitro preclinical 3D NASH model by coculturing primary human hepatocytes, human stellate cells, liver endothelial cells and Kupffer cells embedded in a hydrogel of rat collagen on a 96-well plate. A NASH-like environment was induced by addition of medium containing free fatty acids and tumor necrosis factor-α. This model was then characterized by biochemical, imaging and transcriptomics analyses. Results: We succeeded in defining suitable culture conditions to maintain the 3D coculture for up to 10 days in vitro, with the lowest level of steatosis and reproducible low level of inflammation and fibrosis. NASH disease was induced with a custom medium mimicking NASH features. The cell model exhibited the key NASH disease phenotypes of hepatocyte injury, steatosis, inflammation, and fibrosis. Hepatocyte injury was highlighted by a decrease of CYP3A4 expression and activity, without loss of viability up to day 10. Moreover, the model was able to stimulate a stable inflammatory and early fibrotic environment, with expression and secretion of several cytokines. A global gene expression analysis confirmed the NASH induction. Conclusions: This is a new in vitro model of NASH disease consisting of four human primary cell-types that exhibits most features of the disease. The 10-day cell viability and cost effectiveness of the model make it suitable for medium throughput drug screening and provide attractive avenues to better understand disease physiology and to identify and characterize new drug targets.

The Novel Phosphate and Bile Acid Sequestrant Polymer SAR442357 Delays Disease Progression in a Rat Model of Diabetic Nephropathy

As a gut-restricted, nonabsorbed therapy, polymeric bile acid sequestrants (BAS) play an important role in managing hyperlipidemia and hyperglycemia. Similarly, nonabsorbable sequestrants of dietary phosphate have been used for the management of hyperphosphatemia in end-stage renal disease. To evaluate the potential utility of such polymer sequestrants to treat type 2 diabetes (T2D) and its associated renal and cardiovascular complications, we synthesized a novel polymeric sequestrant, SAR442357, possessing optimized bile acid (BA) and phosphate sequestration characteristics. Long-term treatment of T2D obese ^cZucker fatty/Spontaneously hypertensive heart failure F1 hybrid (ZSF1) with SAR442357 resulted in enhanced sequestration of BAs and phosphate in the gut, improved glycemic control, lowering of serum cholesterol, and attenuation of diabetic kidney disease (DKD) progression. In comparison, colesevelam, a BAS with poor phosphate binding properties, did not prevent DKD progression, whereas losartan, an angiotensin II receptor blocker that is widely used to treat DKD, showed no effect on hyperglycemia. Analysis of hepatic gene expression levels of the animals treated with SAR442357 revealed upregulation of genes responsible for the biosynthesis of cholesterol and BAs, providing clear evidence of target engagement and mode of action of the new sequestrant. Additional hepatic gene expression pathway changes were indicative of an interruption of the enterohepatic BA cycle. Histopathological analysis of ZSF1 rat kidneys treated with SAR442357 further supported its nephroprotective properties. Collectively, these findings reveal the pharmacological benefit of simultaneous sequestration of BAs and phosphate in treating T2D and its associated comorbidities and cardiovascular complications. SIGNIFICANCE STATEMENT: A new nonabsorbed polymeric sequestrant with optimum phosphate and bile salt sequestration properties was developed as a treatment option for DKD. The new polymeric sequestrant offered combined pharmacological benefits including glucose regulation, lipid lowering, and attenuation of DKD progression in a single therapeutic agent.

Incretin combination therapy for the treatment of non-alcoholic steatohepatitis

AIMS

To test specific mono-agonists to the glucagon-like peptide-1 receptor (GLP-1R), glucagon receptor (GCGR) and glucose-dependent insulinotropic peptide receptor (GIPR), individually and in combination, in a mouse model of diet-induced non-alcoholic steatohepatitis (NASH) and fibrosis in order to decipher the contribution of their activities and potential additive effects to improving systemic and hepatic metabolism.

MATERIALS AND METHODS

We induced NASH by pre-feeding C57BL/6J mice a diet rich in fat, fructose and cholesterol for 36 weeks. This was followed by 8 weeks of treatment with the receptor-specific agonists 1-GCG (20 μg/kg twice daily), 2-GLP1 (3 μg/kg twice daily) or 3-GIP (30 μg/kg twice daily), or the dual (1 + 2) or triple (1 + 2 + 3) combinations thereof. A dual GLP-1R/GCGR agonistic peptide, 4-dual-GLP1/GCGR (30 μg/kg twice daily), and liraglutide (100 μg/kg twice daily) were included as references.

RESULTS

Whereas low-dose 1-GCG or 3-GIP alone did not influence body weight, liver lipids and histology, their combination with 2-GLP1 provided additional weight loss, reduction in liver triglycerides and improvement in histological disease activity score. Notably, 4-dual-GLP-1R/GCGR and the triple combination of selective mono-agonists led to a significantly stronger reduction in the histological non-alcoholic fatty liver disease activity score compared to high-dose liraglutide, at the same extent of body weight loss.

CONCLUSIONS

GCGR and GIPR agonism provide additional, body weight-independent improvements on top of GLP-1R agonism in a murine model of manifest NASH with fibrosis.

A simple-architecture fibered transmission system for dissemination of high stability 100 MHz signals

We report on the development of a simple-architecture fiber-based frequency distribution system used to transfer high frequency stability 100 MHz signals. This work is focused on the emitter and the receiver performances that allow the transmission of the radio-frequency signal over an optical fiber. The system exhibits a residual fractional frequency stability of 1 × 10^-14 at 1 s integration time and in the low 10^-16 range after 100 s. These performances are suitable to transfer the signal of frequency references such as those of a state-of-the-art hydrogen maser without any phase noise compensation scheme. As an application, we demonstrate the dissemination of such a signal through a 100 m long optical fiber without any degradation. The proposed setup could be easily extended for operating frequencies in the 10 MHz-1 GHz range.

Association study in three different populations between the GPR88 gene and major psychoses

GPR88, coding for a G protein-coupled orphan receptor that is highly represented in the striatum, is a strong functional candidate gene for neuropsychiatric disorders and is located at 1p22-p21, a chromosomal region that we have previously linked to bipolar disorder (BD) in the Sardinian population. In order to ascertain the relevance of GPR88 as a risk factor for psychiatric diseases, we performed a genetic association analysis between GPR88 and BD in a sample of triads (patient and both parents) recruited in the Sardinian and the Palestinian population as well as between GPR88 and schizophrenia (SZ) in triads from the Xhosa population in South Africa. We found a positive association between GPR88 and BD in the Sardinian and Palestinian triads. Moreover, we found a positive association between GPR88 and SZ in triads from the Xhosa population in South Africa. When these results were corrected for multiple testing, the association between GPR88 and BD was maintained in the Palestinian population. Thus, these results suggest that GPR88 deserves consideration as a candidate gene for psychiatric diseases and requires to be further investigated in other populations.

Mitochondrial energetic and AKT status mediate metabolic effects and apoptosis of metformin in human leukemic cells

Previous reports demonstrate that metformin, an anti-diabetic drug, can decrease the risk of cancer and inhibit cancer cell growth. However, its mechanism in cancer cells is still unknown. Metformin significantly blocks cell cycle and inhibits cell proliferation and colony formation of leukemic cells. However, the apoptotic response to metformin varies. Furthermore, daily treatment with metformin induces apoptosis and reduces tumor growth in vivo. While metformin induces early and transient activation of AMPK, inhibition of AMPKα1/2 does not abrogate anti-proliferative or pro-apoptotic effects of metformin. Metformin decreases electron transport chain complex I activity, oxygen consumption and mitochondrial ATP synthesis, while stimulating glycolysis for ATP and lactate production, pentose phosphate pathway for purine biosynthesis, fatty acid metabolism, as well as anaplerotic and mitochondrial gene expression. Importantly, leukemic cells with high basal AKT phosphorylation, glucose consumption or glycolysis exhibit a markedly reduced induction of the Pasteur effect in response to metformin and are resistant to metformin-induced apoptosis. Accordingly, glucose starvation or treatment with deoxyglucose or an AKT inhibitor induces sensitivity to metformin. Overall, metformin elicits reprogramming of intermediary metabolism leading to inhibition of cell proliferation in all leukemic cells and apoptosis only in leukemic cells responding to metformin with AKT phosphorylation and a strong Pasteur effect.

Generation of a drug-inducible reporter system to study cell reprogramming in human cells

BACKGROUND

Strategies on the basis of doxycycline-inducible lentiviruses in mouse cells allowed the examination of mechanisms governing somatic cell reprogramming.

RESULTS

Using a doxycycline-inducible human reprogramming system, we identified unreported miRs enhancing reprogramming efficiency.

CONCLUSION

We generated a drug-inducible human reprogramming reporter system as an invaluable tool for genetic or chemical screenings.

SIGNIFICANCE

These cellular systems provide a tool to enable the advancement of reprogramming technologies in human cells. Reprogramming of somatic cells into induced pluripotent stem cells is achieved by the expression of defined transcription factors. In the last few years, reprogramming strategies on the basis of doxycycline-inducible lentiviruses in mouse cells became highly powerful for screening purposes when the expression of a GFP gene, driven by the reactivation of endogenous stem cell specific promoters, was used as a reprogramming reporter signal. However, similar reporter systems in human cells have not been generated. Here, we describe the derivation of drug-inducible human fibroblast-like cell lines that express different subsets of reprogramming factors containing a GFP gene under the expression of the endogenous OCT4 promoter. These cell lines can be used to screen functional substitutes for reprogramming factors or modifiers of reprogramming efficiency. As a proof of principle of this system, we performed a screening of a library of pluripotent-enriched microRNAs and identified hsa-miR-519a as a novel inducer of reprogramming efficiency.

No replication of genetic association between candidate polymorphisms and Alzheimer's disease

Alzheimer's disease is a genetically complex disorder, for which new putative susceptibility genes are constantly proposed in the literature. We selected 16 candidate genes involved in biological pathways closely related to the pathology, and for which a genetic association with Alzheimer's disease was previously detected: ACE, BACE1, BDNF, ECE1, HSPG2, IDE, IL1a, IL6, IL10, MAPT, PLAU, PrnP, PSEN1, SORL1, TFCP2 and TGFb1. The variants originally associated with the disease were genotyped in a French Caucasian sample including 428 cases and 475 controls and tested for association in order to replicate the initial results. Despite a careful replication study design, we failed to validate the initial findings for any of these variants, with the possible exception of MAPT, SORL1 and TFCP2 for which some nominal but inconsistent evidence of association was observed.

Physiological diversity of mitochondrial oxidative phosphorylation

To investigate the physiological diversity in the regulation and control of mitochondrial oxidative phosphorylation, we determined the composition and functional features of the respiratory chain in muscle, heart, liver, kidney, and brain. First, we observed important variations in mitochondrial content and infrastructure via electron micrographs of the different tissue sections. Analyses of respiratory chain enzyme content by Western blot also showed large differences between tissues, in good correlation with the expression level of mitochondrial transcription factor A and the activity of citrate synthase. On the isolated mitochondria, we observed a conserved molar ratio between the respiratory chain complexes and a variable stoichiometry for coenzyme Q and cytochrome c, with typical values of [1-1.5]:[30-135]:[3]:[9-35]:[6.5-7.5] for complex II:coenzyme Q:complex III:cytochrome c:complex IV in the different tissues. The functional analysis revealed important differences in maximal velocities of respiratory chain complexes, with higher values in heart. However, calculation of the catalytic constants showed that brain contained the more active enzyme complexes. Hence, our study demonstrates that, in tissues, oxidative phosphorylation capacity is highly variable and diverse, as determined by different combinations of 1) the mitochondrial content, 2) the amount of respiratory chain complexes, and 3) their intrinsic activity. In all tissues, there was a large excess of enzyme capacity and intermediate substrate concentration, compared with what is required for state 3 respiration. To conclude, we submitted our data to a principal component analysis that revealed three groups of tissues: muscle and heart, brain, and liver and kidney.

Working memory deficits in adult rats after prenatal disruption of neurogenesis

We investigated the cognitive consequences of a prenatal injection of the mitotic inhibitor methylazoxymethanol (MAM) into pregnant rats at embryonic day 15 (E15) or 17 (E17). The male offspring were tested when adult on a version of the radial-arm maze task that assesses spatial working memory with an extended delay, where performance is dependent, in part, on the hippocampal-prefrontal circuit. A major impairment of spatial learning was observed in E15 MAM rats. However, the E17 MAM rats did learn the rule but were impaired selectively in the 30-min delay-interposed task. Morphologically, the E15 MAM rats exhibited dramatic gross brain abnormalities, whereas the E17 MAM animals displayed aberrant cell migration in the hippocampus and a disrupted laminar pattern in the neocortex. These results suggest that late gestational MAM injection (E17) causes a cognitive impairment in a prefrontal cortex-hippocampus-dependent working memory task. This approach could provide a new developmental model of disorders associated with working memory deficits, such as schizophrenia.

The Mtr2-Mex67 NTF2-like Domain Complex

The formation of the Mtr2-Mex67 heterodimer is essential for yeast mRNA export as it constitutes a key nuclear component for shuttling mRNA between the nuclear and cytoplasm compartments through the nuclear pore complex. We report the crystal structures of apo-Mtr2 from the human pathogen Candida albicans and of its complex with the Mex67 NTF2-like domain. Compared with other members of the NTF2 fold family, Mtr2 displays novel structural features involved in the nuclear export of the large ribosomal subunit and consistent with a dual functional role of Mtr2 during yeast nuclear export events. The structure of the Mtr2-Mex67 NTF2-like domain complex, which overall is similar to those of the human and Saccharomyces cerevisiae homologs, unveils three putative Phe-Gly repeat binding sites, of which one contributes to the heterodimer interface. These structures exemplify an unrecognized adaptability of the NTF2 building block in evolution, identify novel structural determinants associated with key biological functions at the molecular surface of the yeast Mtr2-Mex67 complex, and suggest that the yeast and human mRNA export machineries may differ.

Sarcolemma phospholipid structure investigated by immunogold electron microscopy and (31)P NMR spectroscopy with lanthanide ions

The biological functions of plasma membranes depend greatly on the biophysical properties resulting from protein and phospholipid structure. We investigated the phospholipid structure of the normal sarcolemma membrane, which is known to be highly dysfunctional in myopathies. Combining electron microscopy and (31)P nuclear magnetic resonance (NMR) spectroscopy on isolated sarcolemma vesicles, we find that (i) the sarcolemma vesicles maintain the in-vivo cellular sidedness, (ii) the phospholipid mobility is close to that observed in model membranes (similar lateral diffusion coefficients and spin-lattice T(1) relaxation times). Using broad-band and magic angle spinning (31)P NMR spectroscopy with lanthanide ions (Pr(3+)), it is possible to quantify the distribution of phospholipids between internal and external membrane layers, showing that the trans-bilayer distribution is highly asymmetrical.

Initiation of DNA replication by DNA polymerases from primers forming a triple helix

Despite extensive studies on oligonucleotide-forming triple helices, which were discovered in 1957, their possible relevance in the initiation of DNA replication remains unknown. Using sequences forming triple helices, we have developed a DNA polymerisation assay by using hairpin DNA templates with a 3' dideoxynucleotide end and an unpaired 5'-end extension to be replicated. The T7 DNA polymerase successfully elongated nucleotides to the expected size of the template from the primers forming triple helices composed of 9-14 deoxyguanosine-rich residues. The triple helix-forming primer required for this reaction has to be oriented parallel to the homologous sequence of the hairpin DNA template. Substitution of the deoxyguanosine residues by N7 deazadeoxyguanosines in the hairpin of the template prevented primer elongation, suggesting that the formation of a triple helix is a prerequisite for primer elongation. Furthermore, DNA sequencing could be achieved with the hairpin template through partial elongation of the third DNA strand forming primer. The T4 DNA polymerase and the Klenow fragment of DNA polymerase I provided similar DNA elongation to the T7 polymerase-thioredoxin complex. On the basis of published crystallographic data, we show that the third DNA strand primer fits within the catalytic centre of the T7 DNA polymerase, thus underlying this new property of several DNA polymerases which may be relevant to genome rearrangements and to the evolution of the genetic apparatus, namely the DNA structure and replication processes.

Effects of repeated systemic administration of d-Fenfluramine on serotonin and glutamate release in rat ventral hippocampus: comparison with methamphetamine using in vivo microdialysis

We compared the effects of three systemic injections of various doses of d-Fenfluramine, an indirect serotonergic agonist (1.3, 5 or 10 mg/kg), to those of a known neurotoxin, methamphetamine (METH, at a 7.5 mg/kg dose), given i.p. at 2-h intervals, simultaneously on extracellular levels of glutamate [Gluext] and 5-HT [5-HText] in the ventral hippocampus (VHPC) using in vivo microdialysis in conscious rats. METH markedly increased both [Gluext] (+77% over the control value in saline-treated rats) and [5-HText] (around +250% over controls) in the VHPC. d-Fenfluramine, at all the doses studied, induced gradual increases of [5-HText] in the VHPC (between +125% and +417% over control values), but did not modify [Gluext]. These data highlight marked in vivo differences between METH and d-Fenfluramine in their effects on extracellular levels of 5-HT and Glu in the rat ventral hippocampus following their repeated systemic administration.

What do mitochondrial diseases teach us about normal mitochondrial functions...that we already knew: threshold expression of mitochondrial defects

This paper shows how metabolic control analysis (MCA) can help to explain two important features of mitochondrial diseases: (i) the existence of a threshold in the expression of the complex deficiencies on the respiratory flux or on ATP synthesis, i.e. the fact that it is necessary to have a large complex deficiency in order to observe a substantial decrease in these fluxes; (ii) the tissue specificity, i.e. the fact that all tissues are not affected, even if the complex deficiency is present in all of them. We also show the limits of MCA, particularly when considering the in vivo situation. However, MCA offers a new way to consider mitochondrial diseases. The fact that fluxes only slightly change, when a complex is affected, is done at the expense of great changes in intermediate metabolite concentrations; intermediate metabolites situated upstream from the deficient complex are more reduced, leading to a greater generation of free radicals. This could bring an explanation for the diseases observed in conditions where the mitochondrial rate of ATP synthesis is only slightly affected.

Tissue variation in the control of oxidative phosphorylation: implication for mitochondrial diseases

Metabolic control analysis has often been used for quantitative studies of the regulation of mitochondrial oxidative phosphorylations (OXPHOS). The main contribution of this work has been to show that the control of mitochondrial metabolic fluxes can be shared among several steps of the oxidative phosphorylation process, and that this distribution can vary according to the steady state and the tissue. However, these studies do not show whether this observed variation in the OXPHOS control is due to the experimental conditions or to the nature of the mitochondria. To find out if there actually exists a tissue variation in the distribution of OXPHOS control coefficients, we determined the control coefficients of seven OXPHOS complexes on the oxygen-consumption flux in rat mitochondria isolated from five different tissues under identical experimental conditions. Thus in this work, only the nature of the mitochondria can be responsible for any variation detected in the control coefficient values between different tissues. The analysis of control coefficient distribution shows two tissue groups: (i) the muscle and the heart, controlled essentially at the level of the respiratory chain; and (ii) the liver, the kidney and the brain, controlled mainly at the phosphorylation level by ATP synthase and the phosphate carrier. We propose that this variation in control coefficient according to the tissue origin of the mitochondria can explain part of the tissue specificity observed in mitochondrial cytopathies.

Effect of a pulsed magnetic field and of first cold-pressure sunflower oil on mice

In previous studies it has been shown that exposure of mice to a 12-Hz 6 mT unipolar square pulsed magnetic field (PMF) suppressed the excess of weight due to application of 1st cold-pressure sunflower oil. This time we considered the effect of oil and/or PMF on the growing curves lifespans of mice. The exposure took place for 30 min 5 days a week, from the 7th week of life to death. The results are 1) a broken slope in the growing curves from the 125th day of aging: the exposed mice were lighter than the controls, keeping the differences between the growing curves needed a repeated exposure all life long; 2) a significant increase in the lifespan of the controls which received oil versus the controls which received water; 3) an increase in the lifespan of the exposed mice versus the non-exposed control batches. On one hand it has been reported that essential polyunsaturated fatty acids found in first cold-pressure sunflower oil played a prominent role in membrane structures and in immune equilibrium. On the other hand, it was shown that oscillating electric fields could activate Na+K+-ATPase.

Simultaneous effects of local dexfenfluramine application on extracellular glutamate and serotonin levels in rat frontal cortex: a reverse microdialysis study

We examined the effects of local perfusion by reverse dialysis of various doses of dexfenfluramine (D-fen; in mM: 2.4, 12, and 24) simultaneously on serotonin (5-HT; [5-HT]ext) and glutamate (Glu; [Glu]ext) extracellular levels in the frontal cortex of awake rats. D-fen induced a dose-dependent increase in both [5-HT]ext and [Glu]ext, the latter being Ca2+ -dependent and TTX-sensitive, while the former is not. Pretreatment with either the neurotoxin p-chloroamphetamine or the 5-HT uptake blocker fluoxetine, markedly reduced the effects of D-fen on [5-HT]ext and [Glu]ext compared to controls. This indicates that intact 5-HT nerve terminals may be required for D-fen to enter into neurones to release 5-HT by reversal of the 5-HT transporter, which then increases frontocortical [Glu]ext. Pretreatment with the Glu uptake blocker, L-trans-pyrrolidine-2,4-dicarboxylic acid (1 mM), significantly reduced by 40% the effect of D-fen's on [Glu]ext suggesting that Glu uptake sites are partially involved in this effect. These results strongly suggest that intracortical application, by reverse dialysis, of a high dose of D-fen increases frontocortical [Glu]ext by a dual mechanism of action: (1) by stimulating 5-HT release (a major indirect effect) that, in turn, facilitates the release of neuronal Glu; (2) by reversal of the glutamate transporter (a minor direct effect being Ca2+ -independent and TTX-insensitive).

Mitochondrial creatine kinase functional development in post-natal rat skeletal muscle. A combined polarographic/31P NMR study

Mitochondrial creatine kinase (Mi-CK) function in viable mitochondria from developing rat skeletal muscle was assessed both by polarographic measurements of creatine-induced respiration and 31P NMR spectroscopy measurements of phosphocreatine (PCr) synthesis. Creatine-induced respiration was observed in very young rats and increased by 50% to 35 days of age. PCr synthesis was present in 7 day old animals and increased by 300% reaching levels measured in 35 day and adult muscle. Unlike reports showing Mi-CK enzymatic activities but no mitochondrial function in several situations, a concomitant progression of enzymatic activity and mitochondrial function was evidenced during the developmental stages of skeletal muscle Mi-CK in altricious animals. These results correlated with the progressive pattern of muscle differentiation during development of motricity in such animals. The observation that Mi-CK is functional in skeletal muscle mitochondria very early after birth, strongly favors the notion that adaptations in skeletal muscle of Mi-CK knock-out mice occur early.

Effect of pulsed magnetic fields on triglyceride and cholesterol levels in plasma of rats

BACKGROUND

Liver is a crucial organ in metabolism. For instance liver is the main source of circulating lipoproteins.

METHODS

In this paper cholesterol and triglyceride plasma levels were measured in male rats previously exposed to pulsed magnetic fields (PMF) used in therapy. Rats underwent a one-hour exposure to a 6 mT 12 Hz PMF.

RESULTS

Twenty-four hours after the end of the exposure to the PMF the rats' livers were heavier, cholesterol and triglyceride plasma levels decreased. All these variations were significantly different according to a variance ratio test as was a rebound in triglyceride level 48 hours after the end of the exposure. Normal values were observed 48 and 96 hours after the end of exposure respectively for cholesterol and triglycerides.

CONCLUSIONS

These alterations may be due to a reversible accumulation of either triglycerides or of their precursors in liver following acute exposure to a 12 Hz PMF.

Identification of five new genes, closely related to the interleukin-1beta converting enzyme gene, that do not encode functional proteases

Interleukin-1beta converting enzyme (ICE) was the first identified member of a growing family of cysteine proteases that now includes ten mammalian homologs. Within this large family, two functional proteins, denoted TX and TY share 60% amino-acid identity with ICE in the mature protein and, together with ICE, constitute the ICE subfamily. The present study describes the identification of five new gene sequences, denoted S1-S5, closely related to ICE and TX and belonging to this subfamily. Sequences were identified using genomic Southern-blot analysis of human DNA with probes corresponding to ICE and TX exon 6. Using PCR amplification and cloning, the complete exon-6 sequence of these new genes was identified; three exhibit around 90% identity with Ice within exon 6, whereas the two others share about 70% identity with Ice. Examination of open reading frames and of amino acids essential for ICE activity indicate that none of these genes encodes for a functional protease. In conclusion, extensive analysis of the genes closely related to Ice shows that the Ice subfamily is constituted of eight members. Three of them encode for functional proteases (ICE, TX and TY) whereas the remaining members probably correspond to pseudogenes.

Microdialysis monitoring of variations in extracellular levels of serotonin, GABA and excitatory amino acids in the frontal cortex of awake rats in response to a single peripheral or central administration of dexfenfluramine

The effects of a single dexfenfluramine (D-fen) administration on the release of endogenous serotonin (5-hydroxytryptamine, 5-HT), excitatory (glutamate, Glu, aspartate, Asp) and inhibitory (gamma-aminobutyric acid, GABA) amino acids from the frontal cortex were studied by using in vivo microdialysis in freely-moving rats. Extracellular levels of these neurotransmitters were measured with HPLC coupled to electrochemical detection or with capillary electrophoresis coupled to laser-induced fluoresence detection (CE-LIFD). In a first study, single intraperitoneal administration of D-fen (0.5, 1.3, 5 and 10 mg/kg) increased extracellular 5-HT levels in a dose-dependent manner (maximal increase by 982% over baseline for the highest dose) while changes in Glu, Asp or GABA never reached statistical significance. In a second study, 73 nM of D-fen applied locally through the frontocortical dialysis probe, at a flow rate of 1.5 microliters/min in 30 microliters of perfusion fluid for 20 min, increased extracellular 5-HT and Asp levels [the maximal increases were to 1804% and 280% of the respective basal values (100%)] without altering extracellular levels of Glu and GABA. Thus, the order of magnitude of the changes induced by systemic administration or local infusion of D-fen on frontocortical extracellular levels of several neurotransmitters (5-HT > > Asp > GABA = Glu) demonstrate that D-fen, an indirect serotoninergic agonist, mainly increases 5-HT release while producing slight (Asp) or no (Glu, GABA) short-term in vivo variations in amino acid extracellular levels in the rat frontal cortex.

The effect of a pulsed magnetic field and that of methyl-silane triol on galactosamine induced hepatitis among rats

Liver cell necrosis was induced in rats by a galactosamine injection. Cell death was due to an increase of Ca++ intracellular levels and was also under the control of genes. Rats were then either exposed or not to a 6 mT 100 HZ pulsed magnetic field (PMF) and they either received or not methylsilane-triol injections. Animals were sacrificed twenty-seven hours after a galactosamine injection. On the one hand it appeared from transaminase levels that the PMF increased the number of animals which were sensitized to galactosamine but decreased transaminase levels. On the other hand PMF decreased the protective effect of MST against galactosamine. We may suggest that PMF should be considered as an additional cellular signal received through genes which would determine the evolution towards or against apoptosis according to the age of the cell itself but also the Ca++ intracellular level.

Effect of Pulsed Magnetic Fields on Cholesterol and Tryglyceride Levels in Rats Study of Field Intensity and Length of Exposure

In a previous work a decrease in cholesterol and triglyceride plasma levels was observed in rats 24 hours after their exposure to a 12 Hz 6 mT pulsed magnetic field (PMF). This time, a study of intensity effects of a 12 Hz PMF for a sixty-minute exposure and of length of exposure for a 12 Hz 6 mT PMF took place. Non-linear effect-dose relationships were ob­ served for the PMF intensity as well as for the length of exposure used. The highest decreases in cholesterol and triglyceride levels were obtained after to a sixty-minute exposure with 1.5 mT and 12 mT.

Effect of pulsed magnetic fields on cholesterol and tryglyceride levels in rats study of field intensity and length of exposure

In a previous work a decrease in cholesterol and triglyceride plasma levels was observed in rats 24 hours after their exposure to a 12 Hz 6 mT pulsed magnetic field (PMF). This time, a study of intensity effects of a 12 Hz PMF for a sixty-minute exposure and of length of exposure for a 12 Hz 6 mT PMF took place. Non-linear effect-dose relationships were observed for the PMF intensity as well as for the length of exposure used. The highest decreases in cholesterol and triglyceride levels were obtained after to a sixty-minute exposure with 1.5 mT and 12 mT.

Exposure of mice to pulsed magnetic fields: long-term observations

This work was undertaken to check the effects of 460 Hz pulsed magnetic fields (PMF) on the growth curves of mice, and to observe any possible long term effect. Effects on the growth curves have already been shown in young female AKR mice. Eight-week-old Swiss female mice underwent, until death, a twice weekly a one-hour-exposure to a 460 Hz 6 mT PMF. They initially showed slower than that of the controls, but it later became faster, 460 Hz 9 mT PMF always kept the growth curves of the exposed mice under those of the controls. However, no difference with controls was noticed when the mice were exposed after the thirtieth week. Moreover, there was no difference in the survival or in pathological aspects between the exposed mice and controls.

Fine specificity of monoclonal antibodies directed at human T cell receptor variable regions: comparison with oligonucleotide-driven amplification for evaluation of V beta expression

Seven distinct anti-human T cell receptor (TcR) V region monoclonal antibodies (mAb) were generated by immunizing mice with either human T cell lines or transfected murine cells expressing human TcR V beta genes. The specificity of these reagents was determined as follows: T cells recognized by each mAb were purified from the peripheral blood of healthy donors and TcR transcripts expressed in these cells were analyzed using oligonucleotide-driven amplification and cDNA sequencing. Four mAb were found to delineate the V beta 3, V beta 8, V beta 17 and V beta 19 subfamilies, respectively. The remaining reagents recognize subsets within the V beta 2, V beta 5 and V beta 13 subfamilies. Reactivity of the mAb with circulating T cells from 18 unrelated healthy individuals was determined. Limited variability was found from an individual to another. In four donors, mAb staining was compared to oligonucleotide-driven amplification for evaluation of V beta 3, V beta 8, V beta 17 and V beta 19 subfamily expression in the peripheral blood. Although the V gene subfamily-specific oligonucleotides used in this study belong to a carefully controlled series, our results show that this method does not give an accurate estimate of the percentage of peripheral T cells expressing a given TcR beta chain. The present data confirm the necessity to establish a complete set of well-characterized monoclonal reagents to study human T cell responses.

Purification and properties of a recombinant sulfur analog of murine selenium-glutathione peroxidase

We previously constructed plasmids for synthesis of glutathione-peroxidase (GPx) mutants in an Escherichia coli expression system. In these recombinant proteins either cysteine ([Cys]GPx mutant) or serine ([Ser]GPx mutant) were present in place of the active-site selenocysteine (SeCys) of the natural enzyme. We have now investigated GPx activity of [Cys]GPx and [Ser]GPx mutants. Enzyme assays performed on preparations of these partially purified proteins demonstrated that the [Cys]GPx mutant exhibited a significant GPx activity, unlike the [Ser]GPx mutant. Purification of [Cys]GPx was performed in two steps of ion-exchange chromatography giving a 98% homogenous protein in 50% yield. The purified [Cys]GPx protein was shown to be a symmetrical tetramer by the means of gel-filtration HPLC and SDS/PAGE. Two isoelectric points were found (6.8 and 7.2) which may reflect two different oxidation states of the mutant protein. The GPx activity of the [Cys]GPx mutant was optimal at pH 8.5. The [Cys]GPx mutant had a specific activity approximately 1000-fold smaller than that of the natural enzyme, and was very easily inactivated by hydroperoxides. Inhibition of the activity with iodoacetate determined a pKa of 8.3, presumably that of the active-site cysteine. Unlike that of SeGPx, the GPx activity of [Cys]GPx was only slightly inhibited by mercaptosuccinate. We discuss hypothetical mechanistic constraints of either catalytic cycle, which may explain such results.

Cloning of murine SeGpx cDNA and synthesis of mutated GPx proteins in Escherichia coli

Glutathione peroxidase (GPx) of mammalian cells and Escherichia coli formate dehydrogenase both contain a selenocysteine (SeCys) in their amino acid (aa) sequence. In these two enzymes, this aa is encoded by a UGA codon, which is usually a stop codon for protein synthesis. We constructed plasmids to test the synthesis of GPx in E. coli. These constructions permitted high-level production of GPx mutants, where the SeCys codon was replaced by cysteine (UGC, UGU) or serine (UCA) codons, but synthesis of selenoprotein could not be detected: our data suggest that signals used for the recognition of the UGA codon as a SeCys codon are not conserved between E. coli and mammalian cells.

[Repeated Keratoplasties and graft rejection]

It is always difficult to estimate the risk of recurrence of maladie due greffon in repeat grafts, and the intricate factors in these cases are open to complex analysis. A number of grafts have been divided into those which were repeated on the same eye and those on the two eyes of the same subject. In the majority of cases the grafts were penetrating (105 out of 118 cases), and the overall analysis of the results is dependent on the following factors: -- Grafts performed as primary procedures in one eye or both eyes: if they develop maladie due greffon, it is usually the 'endothelial' form which appears between the first and third month; the prognosis is good (53-66 p. 100 cure with steroid therapy). It was noticed that when grafts were performed on both eyes, there was a risk of developing maladie due greffon on the eye with the first graft simultaneously if it developed in the second eye. -- Repeated grafts on the same eye caused maladie due greffon of varying types (endothelial, stromal and mixed) with a much earlier occurrence. The prognosis is worse (6 p. 100 cure, 33 p. 100 semi-failure and 60 p. 100 failure). -- Finally repeated grafts on severe leucomas (burns, leucoma adherens, inflammatory keratopathies with active neovascularisation, etc.): these practically all end in failure due either to immunological reactions or inflammatory or cicatrical changes. A table of visual acuities obtained after treatment in cases of cure, incomplete cure and failure is given at the end of this paper.