Integrative systems biology of wheat susceptibility to Fusarium graminearum uncovers a conserved gene regulatory network and identifies master regulators targeted by fungal core effectors

BACKGROUND

Plant diseases are driven by an intricate set of defense mechanisms counterbalanced by the expression of host susceptibility factors promoted through the action of pathogen effectors. In spite of their central role in the establishment of the pathology, the primary components of plant susceptibility are still poorly understood and challenging to trace especially in plant-fungal interactions such as in Fusarium head blight (FHB) of bread wheat. Designing a system-level transcriptomics approach, we leveraged the analysis of wheat responses from a susceptible cultivar facing Fusarium graminearum strains of different aggressiveness and examined their constancy in four other wheat cultivars also developing FHB.

RESULTS

In this study, we describe unexpected differential expression of a conserved set of transcription factors and an original subset of master regulators were evidenced using a regulation network approach. The dual-integration with the expression data of pathogen effector genes combined with database mining, demonstrated robust connections with the plant molecular regulators and identified relevant candidate genes involved in plant susceptibility, mostly able to suppress plant defense mechanisms. Furthermore, taking advantage of wheat cultivars of contrasting susceptibility levels, a refined list of 142 conserved susceptibility gene candidates was proposed to be necessary host's determinants for the establishment of a compatible interaction.

CONCLUSIONS

Our findings emphasized major FHB determinants potentially controlling a set of conserved responses associated with susceptibility in bread wheat. They provide new clues for improving FHB control in wheat and also could conceivably leverage further original researches dealing with a broader spectrum of plant pathogens.

Assessment of Tunisian Trichoderma Isolates on Wheat Seed Germination, Seedling Growth and Fusarium Seedling Blight Suppression

Beneficial microorganisms, including members of the Trichoderma genus, are known for their ability to promote plant growth and disease resistance, as well as being alternatives to synthetic inputs in agriculture. In this study, 111 Trichoderma strains were isolated from the rhizospheric soil of Florence Aurore, an ancient wheat variety that was cultivated in an organic farming system in Tunisia. A preliminary ITS analysis allowed us to cluster these 111 isolates into three main groups, T. harzianum (74 isolates), T. lixii (16 isolates) and T. sp. (21 isolates), represented by six different species. Their multi-locus analysis (tef1, translation elongation factor 1; rpb2, RNA polymerase B) identified three T. afroharzianum, one T. lixii, one T. atrobrunneum and one T. lentinulae species. These six new strains were selected to determine their suitability as plant growth promoters (PGP) and biocontrol agents (BCA) against Fusarium seedling blight disease (FSB) in wheat caused by Fusarium culmorum. All of the strains exhibited PGP abilities correlated to ammonia and indole-like compound production. In terms of biocontrol activity, all of the strains inhibited the development of F. culmorum in vitro, which is linked to the production of lytic enzymes, as well as diffusible and volatile organic compounds. An in planta assay was carried out on the seeds of a Tunisian modern wheat variety (Khiar) by coating them with Trichoderma. A significant increase in biomass was observed, which is associated with increased chlorophyll and nitrogen. An FSB bioprotective effect was confirmed for all strains (with Th01 being the most effective) by suppressing morbid symptoms in germinated seeds and seedlings, as well as by limiting F. culmorum aggressiveness on overall plant growth. Plant transcriptome analysis revealed that the isolates triggered several SA- and JA-dependent defense-encoding genes involved in F. culmorum resistance in the roots and leaves of three-week-old seedlings. This finding makes these strains very promising in promoting growth and controlling FSB disease in modern wheat varieties.

Fusarium graminearum Infection Strategy in Wheat Involves a Highly Conserved Genetic Program That Controls the Expression of a Core Effectome

Fusarium graminearum, the main causal agent of Fusarium Head Blight (FHB), is one of the most damaging pathogens in wheat. Because of the complex organization of wheat resistance to FHB, this pathosystem represents a relevant model to elucidate the molecular mechanisms underlying plant susceptibility and to identify their main drivers, the pathogen’s effectors. Although the F. graminearum catalog of effectors has been well characterized at the genome scale, in planta studies are needed to confirm their effective accumulation in host tissues and to identify their role during the infection process. Taking advantage of the genetic variability from both species, a RNAseq-based profiling of gene expression was performed during an infection time course using an aggressive F. graminearum strain facing five wheat cultivars of contrasting susceptibility as well as using three strains of contrasting aggressiveness infecting a single susceptible host. Genes coding for secreted proteins and exhibiting significant expression changes along infection progress were selected to identify the effector gene candidates. During its interaction with the five wheat cultivars, 476 effector genes were expressed by the aggressive strain, among which 91% were found in all the infected hosts. Considering three different strains infecting a single susceptible host, 761 effector genes were identified, among which 90% were systematically expressed in the three strains. We revealed a robust F. graminearum core effectome of 357 genes expressed in all the hosts and by all the strains that exhibited conserved expression patterns over time. Several wheat compartments were predicted to be targeted by these putative effectors including apoplast, nucleus, chloroplast and mitochondria. Taken together, our results shed light on a highly conserved parasite strategy. They led to the identification of reliable key fungal genes putatively involved in wheat susceptibility to F. graminearum, and provided valuable information about their putative targets.

Proteomics-Based Data Integration of Wheat Cultivars Facing Fusarium graminearum Strains Revealed a Core-Responsive Pattern Controlling Fusarium Head Blight

Fusarium head blight (FHB), mainly occurring upon Fusarium graminearum infection in a wide variety of small-grain cereals, is supposed to be controlled by a range of processes diverted by the fungal pathogen, the so-called susceptibility factors. As a mean to provide relevant information about the molecular events involved in FHB susceptibility in bread wheat, we studied an extensive proteome of more than 7,900 identified wheat proteins in three cultivars of contrasting susceptibilities during their interaction with three F. graminearum strains of different aggressiveness. No cultivar-specific proteins discriminated the three wheat genotypes, demonstrating the establishment of a core proteome regardless of unequivocal FHB susceptibility differences. Quantitative protein analysis revealed that most of the FHB-induced molecular adjustments were shared by wheat cultivars and occurred independently of the F. graminearum strain aggressiveness. Although subtle abundance changes evidenced genotype-dependent responses to FHB, cultivar distinction was found to be mainly due to basal abundance differences, especially regarding the chloroplast functions. Integrating these data with previous proteome mapping of the three F. graminearum strains facing the three same wheat cultivars, we demonstrated strong correlations between the wheat protein abundance changes and the adjustments of fungal proteins supposed to interfere with host molecular functions. Together, these results provide a resourceful dataset that expands our understanding of the specific molecular events taking place during the wheat-F. graminearum interaction.

Searching for FHB Resistances in Bread Wheat: Susceptibility at the Crossroad

Fusarium head blight (FHB), primarily caused by Fusarium graminearum, is one of the most devastating fungal wheat diseases. During the past decades, many efforts have been deployed to dissect FHB resistance, investigating both the wheat responses to infection and, more recently, the fungal determinants of pathogenicity. Although no total resistance has been identified so far, they demonstrated that some plant functions and the expression of specific genes are needed to promote FHB. Associated with the increasing list of F. graminearum effectors able to divert plant molecular processes, this fact strongly argues for a functional link between susceptibility-related factors and the fate of this disease in wheat. In this review, we gather more recent data concerning the involvement of plant and fungal genes and the functions and mechanisms in the development of FHB susceptibility, and we discuss the possibility to use them to diversify the current sources of FHB resistance.

Unbalanced Roles of Fungal Aggressiveness and Host Cultivars in the Establishment of the Fusarium Head Blight in Bread Wheat

Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is the foremost destructive disease of cereals worldwide. Effector-like molecules produced by F. graminearum play key roles in the infection process and are assumed to be one of the essential components of the pathogen’s aggressiveness. However, their nature and role in the disease are still largely misunderstood. As a mean to provide relevant information about the molecular determinism of F. graminearum aggressiveness, we surveyed three F. graminearum strains on three wheat cultivars contrasted by their susceptibility to FHB. F. graminearum strains revealed large differences in aggressiveness which were mostly unchanged when facing hosts of contrasted susceptibility, suggesting that their behavior rely on intrinsic determinants. Surveying the fungal mass progress and the mycotoxin production rate in the spikes did not evidence any simple relationship with aggressiveness differences, while clues were found through a qualitative and quantitative characterization of the three strain proteomes established in planta especially with regards to early synthesized putative effectors. Independently of the wheat cultivar, the three F. graminearum strains produced systematically the same protein set during the infection but substantial differences in their abundance enabled the categorization of fungal aggressiveness. Overall, our findings show that the contrasts in F. graminearum aggressiveness were not based on the existence of strain-specific molecules but rather on the ability of the strain to ensure their sufficient accumulation. Protein abundance variance was mostly driven by the strain genetics and part was also influenced by the host cultivar but strain by cultivar interactions were marginally detected, depicting that strain-specific protein accumulations did not depend on the host cultivar. All these data provide new knowledge on fungal aggressiveness determinants and provide a resourceful repertoire of candidate effector proteins to guide further research.

Time-resolved dissection of the molecular crosstalk driving Fusarium head blight in wheat provides new insights into host susceptibility determinism

Fungal plant diseases are controlled by a complex molecular dialogue that involves pathogen effectors able to manipulate plant susceptibility factors at the earliest stages of the interaction. By probing the wheat-Fusarium graminearum pathosystem, we profiled the coregulations of the fungal and plant proteins shaping the molecular responses of a 96-hr-long infection's dynamics. Although no symptoms were yet detectable, fungal biomass swiftly increased along with an extremely diverse set of secreted proteins and candidate effectors supposed to target key plant organelles. Some showed to be early accumulated during the interaction or already present in spores, otherwise stored in germinating spores and detectable in an in vitro F. graminearum exudate. Wheat responses were swiftly set up and were evidenced before any visible symptom. Significant wheat protein abundance changes co-occurred along with the accumulation of putative secreted fungal proteins and predicted effectors. Regulated wheat proteins were closely connected to basal cellular processes occurring during spikelet ontogeny, and particular coregulation patterns were evidenced between chloroplast proteins and fungal proteins harbouring a predicted chloroplast transit peptide. The described plant and fungal coordinated responses provide a resourceful set of data and expand our understanding of the wheat-F. graminearum interaction.

Quantitative Phosphoproteomic Analysis Reveals Shared and Specific Targets of Arabidopsis Mitogen-Activated Protein Kinases (MAPKs) MPK3, MPK4, and MPK6

In Arabidopsis, mitogen-activated protein kinases MPK3, MPK4, and MPK6 constitute essential relays for a variety of functions including cell division, development and innate immunity. Although some substrates of MPK3, MPK4 and MPK6 have been identified, the picture is still far from complete. To identify substrates of these MAPKs likely involved in cell division, growth and development we compared the phosphoproteomes of wild-type and mpk3, mpk4, and mpk6. To study the function of these MAPKs in innate immunity, we analyzed their phosphoproteomes following microbe-associated molecular pattern (MAMP) treatment. Partially overlapping substrates were retrieved for all three MAPKs, showing target specificity to one, two or all three MAPKs in different biological processes. More precisely, our results illustrate the fact that the entity to be defined as a specific or a shared substrate for MAPKs is not a phosphoprotein but a particular (S/T)P phosphorylation site in a given protein. One hundred fifty-two peptides were identified to be differentially phosphorylated in response to MAMP treatment and/or when compared between genotypes and 70 of them could be classified as putative MAPK targets. Biochemical analysis of a number of putative MAPK substrates by phosphorylation and interaction assays confirmed the global phosphoproteome approach. Our study also expands the set of MAPK substrates to involve other protein kinases, including calcium-dependent (CDPK) and sugar nonfermenting (SnRK) protein kinases.

Phosphoproteomic Analysis of Isolated Mitochondria in Yeast

Mitochondria play a central role in cellular energy metabolism and cell death. Deregulation of mitochondrial functions is associated with several human pathologies (neurodegenerative diseases, neuromuscular diseases, type II diabetes, obesity, cancer). The steadily increasing number of identified mitochondrial phosphoproteins, kinases, and phosphatases in recent years suggests that reversible protein phosphorylation plays an important part in the control of mitochondrial processes. In addition, many mitochondrial phosphoproteins probably still remain to be identified, considering that 30% of proteins are expected to be phosphorylated in eukaryotes. In this chapter, we describe two procedures for the analysis of the mitochondrial phosphoproteome. The first one is a qualitative method that combines blue native and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D-BN/SDS-PAGE) and specific phosphoprotein staining. The second one is a quantitative approach that associates mitochondrial peptide labeling, phosphopeptide enrichment, and mass spectrometry.

Transcriptome dynamics of a susceptible wheat upon Fusarium head blight reveals that molecular responses to Fusarium graminearum infection fit over the grain development processes

In many plant/pathogen interactions, host susceptibility factors are key determinants of disease development promoting pathogen growth and spreading in plant tissues. In the Fusarium head blight (FHB) disease, the molecular basis of wheat susceptibility is still poorly understood while it could provide new insights into the understanding of the wheat/Fusarium graminearum (Fg) interaction and guide future breeding programs to produce cultivars with sustainable resistance. To identify the wheat grain candidate genes, a genome-wide gene expression profiling was performed in the French susceptible wheat cultivar, Recital. Gene-specific two-way ANOVA of about 40 K transcripts at five grain developmental stages identified 1309 differentially expressed genes. Out of these, 536 were impacted by the Fg effect alone. Most of these Fg-responsive genes belonged to biological and molecular functions related to biotic and abiotic stresses indicating the activation of common stress pathways during susceptibility response of wheat grain to FHB. This analysis revealed also 773 other genes displaying either specific Fg-responsive profiles along with grain development stages or synergistic adjustments with the grain development effect. These genes were involved in various molecular pathways including primary metabolism, cell death, and gene expression reprogramming. An increasingly complex host response was revealed, as was the impact of both Fg infection and grain ontogeny on the transcription of wheat genes. This analysis provides a wealth of candidate genes and pathways involved in susceptibility responses to FHB and depicts new clues to the understanding of the susceptibility determinism in plant/pathogen interactions.

Transcriptome dynamics of a susceptible wheat upon Fusarium head blight reveals that molecular responses to Fusarium graminearum infection fit over the grain development processes

In many plant/pathogen interactions, host susceptibility factors are key determinants of disease development promoting pathogen growth and spreading in plant tissues. In the Fusarium head blight (FHB) disease, the molecular basis of wheat susceptibility is still poorly understood while it could provide new insights into the understanding of the wheat/Fusarium graminearum (Fg) interaction and guide future breeding programs to produce cultivars with sustainable resistance. To identify the wheat grain candidate genes, a genome-wide gene expression profiling was performed in the French susceptible wheat cultivar, Recital. Gene-specific two-way ANOVA of about 40 K transcripts at five grain developmental stages identified 1309 differentially expressed genes. Out of these, 536 were impacted by the Fg effect alone. Most of these Fg-responsive genes belonged to biological and molecular functions related to biotic and abiotic stresses indicating the activation of common stress pathways during susceptibility response of wheat grain to FHB. This analysis revealed also 773 other genes displaying either specific Fg-responsive profiles along with grain development stages or synergistic adjustments with the grain development effect. These genes were involved in various molecular pathways including primary metabolism, cell death, and gene expression reprogramming. An increasingly complex host response was revealed, as was the impact of both Fg infection and grain ontogeny on the transcription of wheat genes. This analysis provides a wealth of candidate genes and pathways involved in susceptibility responses to FHB and depicts new clues to the understanding of the susceptibility determinism in plant/pathogen interactions.

A proteomics survey on wheat susceptibility to Fusarium head blight during grain development

The mycotoxigenic fungal species Fusarium graminearum is able to attack several important cereal crops, such as wheat and barley. By causing Fusarium Head Blight (FHB) disease, F. graminearum induces yield and quality losses and poses a public health concern due to in planta mycotoxin production. The molecular and physiological plant responses to FHB, and the cellular biochemical pathways used by F. graminearum to complete its infectious process remain still unknown. In this study, a proteomics approach, combining 2D-gel approach and mass spectrometry, has been used to determine the specific protein patterns associated with the development of the fungal infection during grain growth on susceptible wheat. Our results reveal that F. graminearum infection does not deeply alter the grain proteome and does not significantly disturb the first steps of grain ontogeny but impacts molecular changes during the grain filling stage (impact on starch synthesis and storage proteins). The differentially regulated proteins identified were mainly involved in stress and defence mechanisms, primary metabolism, and main cellular processes such as signalling and transport. Our survey suggests that F. graminearum could take advantage of putative susceptibility factors closely related to grain development processes and thus provide new insights into key molecular events controlling the susceptible response to FHB in wheat grains.

A proteomics survey on wheat susceptibility to Fusarium head blight during grain development

The mycotoxigenic fungal species Fusarium graminearum is able to attack several important cereal crops, such as wheat and barley. By causing Fusarium Head Blight (FHB) disease, F. graminearum induces yield and quality losses and poses a public health concern due to in planta mycotoxin production. The molecular and physiological plant responses to FHB, and the cellular biochemical pathways used by F. graminearum to complete its infectious process remain still unknown. In this study, a proteomics approach, combining 2D-gel approach and mass spectrometry, has been used to determine the specific protein patterns associated with the development of the fungal infection during grain growth on susceptible wheat. Our results reveal that F. graminearum infection does not deeply alter the grain proteome and does not significantly disturb the first steps of grain ontogeny but impacts molecular changes during the grain filling stage (impact on starch synthesis and storage proteins). The differentially regulated proteins identified were mainly involved in stress and defence mechanisms, primary metabolism, and main cellular processes such as signalling and transport. Our survey suggests that F. graminearum could take advantage of putative susceptibility factors closely related to grain development processes and thus provide new insights into key molecular events controlling the susceptible response to FHB in wheat grains.

Proteomic and phosphoproteomic analyses of chromatin-associated proteins from Arabidopsis thaliana

The nucleus is the organelle where basically all DNA-related processes take place in eukaryotes, such as replication, transcription, and splicing as well as epigenetic regulation. The identification and description of the nuclear proteins is one of the requisites toward a comprehensive understanding of the biological functions accomplished in the nucleus. Many of the regulatory mechanisms of protein functions rely on their PTMs among which phosphorylation is probably one of the most important properties affecting enzymatic activity, interaction with other molecules, localization, or stability. So far, the nuclear and subnuclear proteome and phosphoproteome of the model plant Arabidopsis thaliana have been the subject of very few studies. In this work, we developed a purification protocol of Arabidopsis chromatin-associated proteins and performed proteomic and phosphoproteomic analyses identifying a total of 879 proteins of which 198 were phosphoproteins that were mainly involved in chromatin remodeling, transcriptional regulation, and RNA processing. From 230 precisely localized phosphorylation sites (phosphosites), 52 correspond to hitherto unidentified sites. This protocol and data thereby obtained should be a valuable resource for many domains of plant research.

Identification of novel PAMP-triggered phosphorylation and dephosphorylation events in Arabidopsis thaliana by quantitative phosphoproteomic analysis

Signaling cascades rely strongly on protein kinase-mediated substrate phosphorylation. Currently a major challenge in signal transduction research is to obtain high confidence substrate phosphorylation sites and assign them to specific kinases. In response to bacterial flagellin, a pathogen-associated molecular pattern (PAMP), we searched for rapidly phosphorylated proteins in Arabidopsis thaliana by combining multistage activation (MSA) and electron transfer dissociation (ETD) fragmentation modes, which generate complementary spectra and identify phosphopeptide sites with increased reliability. Of a total of 825 phosphopeptides, we identified 58 to be differentially phosphorylated. These peptides harbor kinase motifs of mitogen-activated protein kinases (MAPKs) and calcium-dependent protein kinases (CDPKs), as well as yet unknown protein kinases. Importantly, 12 of the phosphopeptides show reduced phosphorylation upon flagellin treatment. Since protein abundance levels did not change, these results indicate that flagellin induces not only various protein kinases but also protein phosphatases, even though a scenario of inhibited kinase activity may also be possible.

Phosphoproteome dynamics upon changes in plant water status reveal early events associated with rapid growth adjustment in maize leaves

Plant growth adjustment during water deficit is a crucial adaptive response. The rapid fine-tuned control achieved at the post-translational level is believed to be of considerable importance for regulating early changes in plant growth reprogramming. Aiming at a better understanding of early responses to contrasting plant water statuses, we carried out a survey of the protein phosphorylation events in the growing zone of maize leaves upon a range of water regimes. In this study, the impact of mild and severe water deficits were evaluated in comparison with constant optimal watering and with recovery periods lasting 5, 10, 20, 30, 45, and 60 min. Using four biological replicates per treatment and a robust quantitative phosphoproteomic methodology based on stable-isotope labeling, we identified 3664 unique phosphorylation sites on 2496 proteins. The abundance of nearly 1250 phosphorylated peptides was reproducibly quantified and profiled with high confidence among treatments. A total of 138 phosphopeptides displayed highly significant changes according to water regimes and enabled to identify specific patterns of response to changing plant water statuses. Further quantification of protein amounts emphasized that most phosphorylation changes did not reflect protein abundance variation. During water deficit and recovery, extensive changes in phosphorylation status occurred in critical regulators directly or indirectly involved in plant growth and development. These included proteins influencing epigenetic control, gene expression, cell cycle-dependent processes and phytohormone-mediated responses. Some of the changes depended on stress intensity whereas others depended on rehydration duration, including rapid recoveries that occurred as early as 5 or 10 mins after rewatering. By combining a physiological approach and a quantitative phosphoproteomic analysis, this work provides new insights into the in vivo early phosphorylation events triggered by rapid changes in plant water status, and their possible involvement in plant growth-related processes.

Increased gelling agent concentration promotes somatic embryo maturation in hybrid larch (Larix × eurolepsis): a 2-DE proteomic analysis

An integrated physiological and proteomic approach was used to investigate the effects of high gellan gum concentration in the medium during maturation of somatic embryos (SE) of hybrid larch, by comparing embryos incubated in media with a high gellan gum concentration (8 g l(-1) ) and the standard concentration (4 g l(-1) ) after 1, 3, 6 and 8 weeks of maturation. Because of the reduced availability of water in the 8 g l(-1) medium, the cultured embryos had a lower osmotic water potential (Ψπ) and water contents, but higher dry weights (DWs), at 8 weeks compared with embryos cultured on the standard medium. The high gellan gum concentration induced a desiccation that is characteristic in zygotic embryo maturation. Total soluble proteins were extracted from SE with trichloroacetic acid (TCA)-acetone after 1 and 8 weeks of maturation on media with 4 and 8 g l(-1) of gellan gum, and separated by two-dimensional gel electrophoresis (2-DE) at pH 4-7. More than 1100 proteins were reproducibly detected on each gel. At 1 and 8 weeks respectively, the abundances of 62 and 49 spots detected in analyses of embryos matured at the two gellan gum concentrations, significantly differed. Among 62 significantly differing spots at 1 week of maturation, the corresponding proteins of 56 were reliably identified by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), and were found to be mainly involved in 'carbohydrate metabolism', 'genetic information processing' or 'environmental information processing' according to kegg taxonomy. Both physiological parameters and the proteins identified suggested that the embryos were stressed when they were cultured on 4 g l(-1) of gellan gum.

Genetic variation and drought response in two Populus x euramericana genotypes through 2-DE proteomic analysis of leaves from field and glasshouse cultivated plants

Genotype and water deficit effects on leaf 2-DE protein profiles of two Populus deltoides x Populus nigra, cv. 'Agathe_F' and 'Cima', were analysed over a short-term period of 18 days in glasshouse using 4-month-old rooted cuttings and over a long-lasting period of 86 days in open field using 4-year-old rooted cuttings. Leaf proteomes were analyzed using two-dimensional gel electrophoresis, and proteins were identified after database searching from MS peptide spectra. A reliable genotype effect was observed in the leaf proteome over experiment locations, water regimes and sampling dates. Quantitative differences between genotypes were found. Most of them corresponded to proteins matching isoforms or post-translational modification variants. However, 'Cima' displayed the highest abundance of antioxidant enzymes. In response to water deficit, about 10% of the reproducible spots significantly varied regardless of the experiment location, among which about 25% also displayed genotype-dependent variations. As a whole, while 'Cima' differed from 'Agathe_F' by increased abundance of enzymes involved in photorespiration and in oxidative stress, 'Agathe_F' was mainly differentiated by increased abundance of enzymes involved in photosynthesis.

Intratumor treatment of C3H mouse mammary carcinoma with 5-fluorouracil adsorbed on activated charcoal particles

A dosage form comprising 5-fluorouracil (5-FU, 25 mg/ml) adsorbed on a suspension of micronized charcoal (100 mg/ml) 2-5 microns in diameter, adsorbing 5-FU in aqueous solution was studied for intratumor treatment of mammary carcinoma in animal experiments. An in vitro desorption method is described to determine the amount of 5-FU adsorbed on activated charcoal particles which would be released once the drug concentration decreased around the charcoal. In vivo results indicate that an intratumor injection of 5-FU adsorbed on activated charcoal particles is a highly effective method for achieving tumor regression without increasing toxicity.

[Comparison of tacrine hepatotoxicity in patients with Alzheimer disease or AIDS]

Previously used in Alzheimer disease Tacrine (THA): tetrahydroaminoacridine has shown a rise of hepatic transaminase enzyme activity (TEA) in 18% of patients for Summers and 19% for Ames. Although studies using THA from USA or Canada have noticed a rise of TEA in 30% of the patients, after a treatment course with French THA we also have noted a rise of TEA in 12% of the Alzheimer patients. However, these secondary effects yielded to the end of treatment. These studies have been done with THA from different origins and different associations. Summers, the Canadian group and the French one have used THA in association with lecithin, when american group study has been made with no additional product. Therefore we have initiated a trial with oral THA in AIDS patients. 52 patients with HIV infection (26 in the IVC1 group and 26 in IVC2 group) have been treated with the same THA as the one used for Alzheimer french group. The common dosage was 150 to 200 mg (3 to 4 of 50 mg dosing capsules per day). The THA has been synthetized such as having an over 99% pureness product. After a period of 260 months/patient no elevation of TEA has been noted in any patients of our group. These results observed in HIV advanced patients with this THA are discordant with the one observed in Alzheimer's study. The dosage used in AIDS is twice higher than the one used for Alzheimer which gives us credit to the lack of hepatic toxicity in HIV advanced patient after 7 months of treatment.

Stability of epinephrine in alkalinized solutions

STUDY OBJECTIVE

Increasing the pH of an epinephrine solution favors its oxidation and may result in a decrease in its biological activity. It is therefore generally assumed that epinephrine and sodium bicarbonate should not be infused in the same IV line during CPR. The aim of this study was to determine the validity of this widely accepted proposition.

DESIGN AND SETTING

Two different commercial solutions of epinephrine differing only in the concentration of sodium metabisulfite (0.46% and 0.02%) were studied. Two dosages of each solution type (1 mg/1 mL and 10 mg/10 mL) were diluted in 250 mL of 8.4% sodium bicarbonate.

MEASUREMENTS AND MAIN RESULTS

The concentration of epinephrine was measured at different times for two weeks. It was found that the concentration of epinephrine decreased slowly to zero after two weeks, and was approximately at 70% and 100% of control values at 30 minutes after alkalinization.

CONCLUSION

It was concluded that epinephrine in an alkaline solution is effectively oxidized but has a slow reaction that may not be clinically relevant over short periods of time.

Factors influencing precipitation of pH-adjusted bupivacaine solutions

Solutions of bupivacaine precipitate when bicarbonate is added. This limits the clinical use of pH-adjustment in optimizing bupivacaine activity. In this study four different bupivacaine solutions were studied with the addition of sodium bicarbonate at 4 degrees C or 20 degrees C. Bupivacaine concentrations remained unchanged after pH-adjustment. Least crystallization was observed with bupivacaine solutions containing a small amount of sodium bicarbonate and stored at 4 degrees C.

Alkalinization of 0.5% lidocaine for intravenous regional anesthesia

Although remaining a controversial issue, alkalinization of lidocaine or bupivacaine may shorten the time to onset and increase the duration of the sensory block. The aim of this study was to evaluate the effect of pH adjustment on the sensory and motor blocks during intravenous regional anesthesia (IVRA) with lidocaine. Thirty-one patients scheduled for minor hand surgery performed under IVRA were randomized into two groups: Group 1 (n = 14): 1% lidocaine, 3 mg/kg, diluted with the same volume of physiological saline solution (pH = 6.63 +/- 0.05), and Group 2 (n = 17): 1% lidocaine, 3 mg/kg, diluted with the same volume of 1.4% sodium bicarbonate (pH = 7.34 +/- 0.05). final concentration of lidocaine was thus 0.5% in both groups. Sensory block was assessed by pinprick every 2 minutes in areas corresponding to six terminal nerves: ulnar, median, radial, musculocutaneous, medial cutaneous nerve of arm and intercostobrachial, and medial cutaneous nerve of forearm. The time between release of tourniquet (at the end of surgery) and appearance of pain was recorded. Motor blockade was evaluated by asking the patient to squeeze strongly a blood pressure cuff previously inflated to 40 mmHg. This maneuver was performed before and every 2 minutes after injection. No statistical differences were found between the two groups whatever the parameter studied. In conclusion, there is no advantage (over plain solutions) to using pH-adjusted lidocaine during IVRA for hand surgery.

Alkalinization of epidural 0.5% bupivacaine for cesarean section

Controversial results have been published in the literature concerning the efficacy of alkalinization of solutions of local anesthetics to shorten the time to onset of sensory block. Fifty-two parturients scheduled for cesarean section at term under epidural anesthesia were randomly allocated to one of four groups: group 1, 0.5% plain bupivacaine (pH = 5.38 +/- 0.05); group 2, 0.5% bupivacaine pH-adjusted with 1.4% sodium bicarbonate (pH = 6.87 +/- 0.01); group 3, 0.5% bupivacaine with 1:200,000 epinephrine (pH = 4.80 +/- 0.04); and group 4, 0.5% bupivacaine pH-adjusted with 1:200,000 epinephrine (pH = 6.68 +/- 0.01). The time to onset of the sensory block was evaluated using a nerve stimulator technique. Motor blockade was assessed using Bromage's scale. No differences in the characteristics of the onset of the sensory block were observed with epinephrine-containing solutions nor with pH-adjusted local anesthetics. The maximal degree of motor blockade was not significantly different in the four groups. We conclude that alkalinization of a 0.5% bupivacaine solution is not an effective way to shorten the latency of epidural block for cesarean section.

Chemical stability of bupivacaine in pH-adjusted solutions

Recent clinical studies have suggested that alkalinization of bupivacaine may shorten the time to onset and lengthen its duration of action. However, addition of sodium bicarbonate to commercially manufactured bupivacaine can rapidly produce precipitation. This study was performed to study the stability and precipitation of bupivacaine solutions 0.25% and 0.50% with and without epinephrine 1:200,000 after alkalinization. The results indicate that alkalinization does not increase precipitation above recommended limits and that the concentration of bupivacaine in solutions is maintained at least 6 h after alkalinization.

Chemical stability of lignocaine (lidocaine) and adrenalin (epinephrine) in pH-adjusted parenteral solutions

Recent clinical studies have shown that alkalinizing lignocaine (lidocaine) solutions is an effective way of shortening the time of onset and increasing the duration of anaesthesia. However, alkalinizing lignocaine solutions raises the problem of the stability of these preparations. Moreover, the adrenalin usually associated with it is unstable in alkalinized solutions designed for peridural injection. This study was performed to define the range of pH over which lignocaine and adrenalin in commercial solution is stable. The results indicate that it is possible to alkalinize lignocaine solutions and that the solutions prepared are stable for at least 6 h.

Direct measurement of the capsular bag

Direct measurement of the capsular bag was performed after extracapsular cataract extraction on 49 cadaver eyes. These lenses had a collapsed bag size of 10.32 +/- 0.42 mm.