New Insights into the Production of Assyrtiko Wines from the Volcanic Terroir of Santorini Island Using Lachancea thermotolerans

Assyrtiko is a rare ancient grape variety of Greece, which is known to produce Protected Designation of Origin (PDO) Santorini white wines. Besides the famous character of the volcanic terroir, Assyrtiko of Santorini is also marked by a low pH value and sharp acidity. The aim of the present study was to apply a new inoculation procedure that modulates the fermentation process by maintaining the unique sensorial characteristics of Assyrtiko wines based on acidity. For this purpose, the Lachancea thermotolerans species, known for the formation of lactic acid, was tested in sequential fermentation with three different Saccharomyces cerevisiae strains. At the end of the fermentation process, implantation control for S. cerevisiae strains (interdelta sequence profile analysis) was performed, oenological parameters were determined according to the OIV protocols, and the volatile compounds produced were measured by gas chromatography-mass spectrometry (GC/MS). Finally, all produced wines were evaluated by quantitative descriptive analysis by two groups of experts; the Greek team of oenologists from Santorini Island specialized in Assyrtiko wines, and the French team of oenologists specialized in wine from Bordeaux. As expected, the inoculated strain was the one that dominated the fermentation process, but nine S. cerevisiae indigenous strains were also identified in the produced wines. Lachancea thermotolerans produced 1 g/L of lactic and also modulated the volatile profile of the wines independently of the S. cerevisiae strain used. The origin of the panelists played an important role in bringing up sensorial traits, such as acidity. Our results led to a new interesting application of L. thermotolerans for white wine production adapted to climate change claims.

Influence of pH on Oenococcus oeni metabolism: Can the slowdown of citrate consumption improve its acid tolerance?

Oenococcus oeni is the lactic acid bacteria most suited to carry out malolactic fermentation in wine, converting L-malic acid into L-lactic acid and carbon dioxide, thereby deacidifying wines. Indeed, wine is a harsh environment for microbial growth, partly because of its low pH. By metabolizing citrate, O. oeni maintains its homeostasis under acid conditions. Indeed, citrate consumption activates the proton motive force, helps to maintain intracellular pH, and enhances bacterial growth when it is co-metabolized with sugars. In addition, citrate metabolism is responsible for diacetyl production, an aromatic compound which bestows a buttery character to wine. However, an inhibitory effect of citrate on O. oeni growth at low pH has been highlighted in recent years. In order to understand how citrate metabolism can be linked to the acid tolerance of this bacterium, consumption of citrate was investigated in eleven O. oeni strains. In addition, malate and sugar consumptions were also monitored, as they can be impacted by citrate metabolism. This experiment highlighted the huge diversity of metabolisms between strains depending on their origin. It also showed the capacity of O. oeni to de novo metabolize certain end-products such as L-lactate and mannitol, a phenomenon never before demonstrated. It also enabled drawing hypotheses concerning the two positive effects that the slowing down of citrate metabolism could have on biomass production and malolactic fermentation occurring under low pH conditions.

Citrate metabolism in lactic acid bacteria: is there a beneficial effect for Oenococcus oeni in wine?

Lactic acid bacteria (LAB) are Gram positive bacteria frequently used in the food industry for fermentation, mainly transformation of carbohydrates into lactic acid. In addition, these bacteria also have the capacity to metabolize citrate, an organic acid commonly found in food products. Its fermentation leads to the production of 4-carbon compounds such as diacetyl, resulting in a buttery flavor desired in dairy products. Citrate metabolism is known to have several beneficial effects on LAB physiology. Nevertheless, a controversial effect of citrate has been described on the acid tolerance of the wine bacterium Oenococcus oeni. This observation raises questions about the effect of citrate on the capacity of O. oeni to conduct malolactic fermentation in highly acidic wines. This review aims to summarize the current understanding of citrate metabolism in LAB, with a focus on the wine bacterium O. oeni. Metabolism with the related enzymes is detailed, as are the involved genes organized in cit loci. The known systems of cit locus expression regulation are also described. Finally, the beneficial effects of citrate catabolism on LAB physiology are reported and the negative impact observed in O. oeni is discussed.

Bioprotection by non-Saccharomyces yeasts in oenology: Evaluation of O2 consumption and impact on acetic acid bacteria

Bioprotection by yeast addition is increasingly used in oenology as an alternative to sulfur dioxide (SO2). Recent studies have also shown that it is likely to consume dissolved O2. This ability could limit O2 for other microorganisms and the early oxidation of the grape must. However, the ability of yeasts to consume O2 in a context of bioprotection was poorly studied so far considering the high genetic diversity of non-Saccharomyces. The first aim of the present study was to perform an O2 consumption rate (OCR) screening of strains from a large multi species collection found in oenology. The results demonstrate significant inter and intra species diversity with regard to O2 consumption. In the must M. pulcherrima consumes O2 faster than Saccharomyces cerevisiae and then other studied non-Saccharomyces species. The O2 consumption was also evaluate in the context of a yeast mix used as industrial bioprotection (Metschnikowia pulcherrima and Torulaspora delbrueckii) in red must. These non-Saccharomyces yeasts were then showed to limit the growth of acetic acid bacteria, with a bioprotective effect comparable to that of the addition of sulfur dioxide. Laboratory experiment confirmed the negative impact of the non-Saccharomyces yeasts on Gluconobacter oxydans that may be related to O2 consumption. This study sheds new lights on the use of bioprotection as an alternative to SO2 and suggest the possibility to use O2 consumption measurements as a new criteria for non-Saccharomyces strain selection in a context of bioprotection application for the wine industry.

Experimental evolution forcing Oenococcus oeni acid tolerance highlights critical role of the citrate locus

Oenococcus oeni is the main lactic acid bacterium associated with malolactic fermentation (MLF) of wines. MLF plays an important role in determining the final quality of wines. Nevertheless, due to the stressful conditions inherent to wine and especially acidity, MLF may be delayed. This study aimed to explore by adaptive evolution improvements in the acid tolerance of starters but also to gain a better understanding of the mechanisms involved in adaptation toward acidity. Four independent populations of the O. oeni ATCC BAA-1163 strain were propagated (approximately 560 generations) in a temporally varying environment, consisting in a gradual pH decrease from pH 5.3 to pH 2.9. Whole genome sequence comparison of these populations revealed that more than 45 % of the substituted mutations occurred in only five loci for the evolved populations. One of these five fixed mutations affects mae, the first gene of the citrate operon. When grown in an acidic medium supplemented with citrate, a significantly higher bacterial biomass was produced with the evolved populations compared to the parental strain. Furthermore, the evolved populations slowed down their citrate consumption at low pH without impacting malolactic performance.

Impact of Lachancea thermotolerans on chemical composition and sensory profiles of Merlot wines

Wines from warm(ing) climates often contain excessive ethanol but lack acidity. The yeast Lachancea thermotolerans can ameliorate such wines due to partial conversion of sugars to lactic acid during alcoholic fermentation. This study compared the performance of five L. thermotolerans strains in two inoculation modalities (sequential and co-inoculation) to Saccharomyces cerevisiae and un-inoculated treatments in high sugar/low acidity Merlot fermentations. The pH and ethanol levels in mixed-culture dry wines were either comparable, or significantly lower than in controls (decrease of up to 0.5 units and 0.90% v/v, respectively). The analysis of volatile compounds revealed marked differences in major flavour-active yeast metabolites, including up to a thirty-fold increase in ethyl lactate in certain L. thermotolerans modalities. The wines significantly differed in acidity perception, alongside 18 other sensory attributes. Together, these results highlight the potential of some L. thermotolerans strains to produce 'fresher' wines with lower ethanol content and improved flavour/balance.

+Brettanomyces bruxellensis Displays Variable Susceptibility to Chitosan Treatment in Wine

Brettanomyces bruxellensis is the main spoilage microbial agent in red wines. The use of fungal chitosan has been authorized since 2009 as a curative treatment to eliminate this yeast in conventional wines and in 2018 in organic wines. As this species is known to exhibit great genetic and phenotypic diversity, we examined whether all the strains responded the same way to chitosan treatment. A collection of 53 strains of B. bruxellensis was used. In the conditions of the reference test, all were at least temporarily affected by the addition of chitosan to wine, with significant decrease of cultivable population. Some (41%) were very sensitive and no cultivable yeast was detected in wine or lees after 3 days of treatment, while others (13%) were tolerant and, after a slight drop in cultivability, resumed growth between 3 and 10 days and remained able to produce spoilage compounds. There were also many strains with intermediate behavior. The strain behavior was only partially linked to the strain genetic group. This behavior was little modulated by the physiological state of the strain or the dose of chitosan used (within the limits of the authorized doses). On the other hand, for a given strain, the sensitivity to chitosan treatment was modulated by the chitosan used and by the properties of the wine in which the treatment was carried out.

Influence of must yeast-assimilable nitrogen content on fruity aroma variation during malolactic fermentation in red wine

This study assessed the impact of must yeast-assimilable nitrogen (YAN) content and lactic acid bacteria (LAB) strains used for malolactic fermentation (MLF) on the formation of substituted esters, as well as the corresponding precursors (substituted acids), to investigate the modulation of fruity expression in red wines. In microvinification experiments, a Merlot must was fermented with an initial YAN content of 111 mg/L, or supplemented up to 165 and 220 mg/L. Two Oenococcus oeni LAB strains were used for MLF. Analytical methods were used to quantify substituted esters, as well as the corresponding acids, including, any enantiomeric forms. YAN supplementation of the must significantly increased concentrations of substituted esters of short- and branched-chain alkyl fatty acids produced during alcoholic fermentation (AF) (up to 67% in samples with the highest nitrogen content) and substituted esters of hydroxycarboxylic acids generated during MLF (up to 58% in samples with the highest nitrogen content). YAN supplementation in the must did not affect substituted acid formation during AF. After MLF, short- and branched-chain alkyl fatty acid levels increased in wines made from musts with the highest nitrogen content (up to 56% in samples with the highest nitrogen content), whereas concentrations of hydroxycarboxylic acids increased (up to 55%) independently of the initial YAN content, highlighting the important role of MLF. (2S)-2-hydroxy-4-methylpentanoic acid was only found in wines after malolactic fermentation, suggesting different pathways for each enantiomer and opening up new prospects for the study of bacterial metabolisms. Moreover, sensory profiles revealed a significant increase in black-berry- and jammy-fruit aromas during MLF and a strong positive correlation between these aromas and the production of substituted esters following must nitrogen supplementation and MLF. Aromatic reconstitutions revealed that variations in the concentrations of substituted esters after MLF impacted the fruity aroma of red wines.

Oenococcus oeni Exopolysaccharide Biosynthesis, a Tool to Improve Malolactic Starter Performance

Oenococcus oeni is the lactic acid bacterium that most commonly drives malolactic fermentation (MLF) in wine. Though the importance of MLF in terms of wine microbial stability and sensory improvement is well established, it remains a winemaking step not so easy to control. O. oeni displays many adaptation tools to resist the harsh wine conditions which explain its natural dominance at this stage of winemaking. Previous findings showed that capsular polysaccharides and endogenous produced dextran increased the survival rate and the conservation time of malolactic starters. In this paper, we showed that exopolysaccharides specific production rates were increased in the presence of single stressors relevant to wine (pH, ethanol). The transcription of the associated genes was investigated in distinct O. oeni strains. The conditions in which eps genes and EPS synthesis were most stimulated were then evaluated for the production of freeze dried malolactic starters, for acclimation procedures and for MLF efficiency. Sensory analysis tests on the resulting wines were finally performed.

New oenological practice to promote non-Saccharomyces species of interest: saturating grape juice with carbon dioxide

Non-Saccharomyces yeast species, naturally found in grape must, may impact wine quality positively or negatively. In this study, a mixture of five non-Saccharomyces species (Torulaspora delbrueckii, Metschnikowia spp., Starmerella bacillaris (formerly called Candida zemplinina), Hanseniaspora uvarum, Pichia kluyveri), mimicking the composition of the natural non-Saccharomyces community found in grape must, was used for alcoholic fermentation. The impact of CO₂ saturation of the grape juice was studied first on this mixture alone, and then in the presence of Saccharomyces cerevisiae. Two isogenic strains of this species were used: the first with a short and the second a long fermentation lag phase. This study demonstrated that saturating grape juice with CO₂ had interesting potential as an oenological technique, inhibiting undesirable species (S. bacillaris and H. uvarum) and stimulating non-Saccharomyces of interest (T. delbrueckii and P. kluyveri). This stimulating effect was particularly marked when CO₂ saturation was associated with the presence of S. cerevisiae with long fermentation lag phase. The direct consequence of this association was an enhancement of 3-SH levels in the resulting wine.

Combined effect of the Saccharomyces cerevisiae lag phase and the non-Saccharomyces consortium to enhance wine fruitiness and complexity

Non-Saccharomyces (NS) species that are either naturally present in grape must or added in mixed fermentation with S. cerevisiae may impact the wine's chemical composition and sensory properties. NS yeasts are prevailing during prefermentation and early stages of alcoholic fermentation. However, obtaining the correct balance between S. cerevisiae and NS species is still a critical issue: if S. cerevisiae outcompetes the non-Saccharomyces, it may minimize their impact, while conversely if NS take over S. cerevisiae, it may result in stuck or sluggish fermentations. Here, we propose an original strategy to promote the non-Saccharomyces consortium during the prefermentation stage while securing fermentation completion: the use of a long lag phase S. cerevisiae. Various fermentations in a Sauvignon Blanc with near isogenic S. cerevisiae displaying short or long lag phase were compared. Fermentations were performed with or without a consortium of five non-Saccharomyces yeasts (Hanseniaspora uvarum, Candida zemplinina, Metschnikowia spp., Torulaspora delbrueckii, and Pichia kluyveri), mimicking the composition of natural NS community in grape must. The sensorial analysis highlighted the positive impact of the long lag phase on the wine fruitiness and complexity. Surprisingly, the presence of NS modified only marginally the wine composition but significantly impacted the lag phase of S. cerevisiae. The underlying mechanisms are still unclear, but it is the first time that a study suggests that the wine composition can be affected by the lag phase duration per se. Further experiments should address the suitability of the use of long lag phase S. cerevisiae in winemaking.

Enhanced 3-Sulfanylhexan-1-ol Production in Sequential Mixed Fermentation with Torulaspora delbrueckii/Saccharomyces cerevisiae Reveals a Situation of Synergistic Interaction between Two Industrial Strains

The aim of this work was to study the volatile thiol productions of two industrial strains of Torulaspora delbrueckii and Saccharomyces cerevisiae during alcoholic fermentation (AF) of Sauvignon Blanc must. In order to evaluate the influence of the inoculation procedure, sequential and simultaneous mixed cultures were carried out and compared to pure cultures of T. delbrueckii and S. cerevisiae. The results confirmed the inability of T. delbrueckii to release 4-methyl-4-sulfanylpentan-2-one (4MSP) and its low capacity to produce 3-sulfanylhexyl acetate (3SHA), as already reported in previous studies. A synergistic interaction was observed between the two species, resulting in higher levels of 3SH (3-sulfanylhexan-1-ol) and its acetate when S. cerevisiae was inoculated 24 h after T. delbrueckii, compared to the pure cultures. To elucidate the nature of the interactions between these two species, the yeast population kinetics were examined and monitored, as well as the production of 3SH, its acetate and their related non-odorous precursors: Glut-3SH (glutathionylated conjugate precursor) and Cys-3SH (cysteinylated conjugate precursor). For the first time, it was suggested that, unlike S. cerevisiae, which is able to metabolize the two precursor forms, T. delbrueckii was only able to metabolize the glutathionylated precursor. Consequently, the presence of T. delbrueckii during mixed fermentation led to an increase in Glut-3SH degradation and Cys-3SH production. This overproduction was dependent on the T. delbrueckii biomass. In sequential culture, thus favoring T. delbrueckii development, the higher availability of Cys-3SH throughout AF resulted in more abundant 3SH and 3SHA production by S. cerevisiae.

Hanseniaspora uvarum from Winemaking Environments Show Spatial and Temporal Genetic Clustering

Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation (AF) which is usually performed by Saccharomyces species. The aim of this study was to characterize the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analyzed using 11 microsatellite markers and a subset of 47 strains were analyzed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localization as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of H. uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase) were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia, and copper addition) on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites) and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed.

Increase of fruity aroma during mixed T. delbrueckii/S. cerevisiae wine fermentation is linked to specific esters enhancement

The aim of this work was to study ester formation and the aromatic impact of Torulaspora delbrueckii when used in association with Saccharomyces cerevisiae during the alcoholic fermentation of must. In order to evaluate the influence of the inoculation procedure, sequential and simultaneous mixed cultures were carried out and compared to pure cultures of T. delbrueckii and S. cerevisiae. Our results showed that mixed inoculations allowed the increase, in comparison to S. cerevisiae pure culture, of some esters specifically produced by T. delbrueckii and significantly correlated to the maximal T. delbrueckii population reached in mixed cultures. Thus, ethyl propanoate, ethyl isobutanoate and ethyl dihydrocinnamate were considered as activity markers of T. delbrueckii. On the other hand, isobutyl acetate and isoamyl acetate concentrations were systematically increased during mixed inoculations although not correlated with the development of either species but were rather due to positive interactions between these species. Favoring T. delbrueckii development when performing sequential inoculation enhanced the concentration of esters linked to T. delbrueckii activity. On the contrary, simultaneous inoculation restricted the growth of T. delbrueckii, limiting the production of its activity markers, but involved a very important production of numerous esters due to more important positive interactions between species. These results suggest that the ester concentrations enhancement via interactions during mixed modalities was due to S. cerevisiae production in response to the presence of T. delbrueckii. Finally, sensory analyses showed that mixed inoculations between T. delbrueckii and S. cerevisiae allowed to enhance the complexity and fruity notes of wine in comparison to S. cerevisiae pure culture. Furthermore, the higher levels of ethyl propanoate, ethyl isobutanoate, ethyl dihydrocinnamate and isobutyl acetate in mixed wines were found responsible for the increase of fruitiness and complexity.

Exopolysaccharide (EPS) synthesis by Oenococcus oeni: from genes to phenotypes

Oenococcus oeni is the bacterial species which drives malolactic fermentation in wine. The analysis of 50 genomic sequences of O. oeni (14 already available and 36 newly sequenced ones) provided an inventory of the genes potentially involved in exopolysaccharide (EPS) biosynthesis. The loci identified are: two gene clusters named eps1 and eps2, three isolated glycoside-hydrolase genes named dsrO, dsrV and levO, and three isolated glycosyltransferase genes named gtf, it3, it4. The isolated genes were present or absent depending on the strain and the eps gene clusters composition diverged from one strain to another. The soluble and capsular EPS production capacity of several strains was examined after growth in different culture media and the EPS structure was determined. Genotype to phenotype correlations showed that several EPS biosynthetic pathways were active and complementary in O. oeni. Can be distinguished: (i) a Wzy -dependent synthetic pathway, allowing the production of heteropolysaccharides made of glucose, galactose and rhamnose, mainly in a capsular form, (ii) a glucan synthase pathway (Gtf), involved in β-glucan synthesis in a free and a cell-associated form, giving a ropy phenotype to growth media and (iii) homopolysaccharide synthesis from sucrose (α-glucan or β-fructan) by glycoside-hydrolases of the GH70 and GH68 families. The eps gene distribution on the phylogenetic tree was examined. Fifty out of 50 studied genomes possessed several genes dedicated to EPS metabolism. This suggests that these polymers are important for the adaptation of O. oeni to its specific ecological niche, wine and possibly contribute to the technological performance of malolactic starters.

Characterization of the yeast ecosystem in grape must and wine using real-time PCR

The complex microbial ecosystem of grape must and wine harbours a wide diversity of yeast species. Specific oligonucleotide primers for real-time quantitative PCR(QPCR) were designed to analyse several important non-Saccharomyces yeasts (Issatchenkia orientalis, Metschnikowia pulcherrima, Torulaspora delbrueckii, Candida zemplinina and Hanseniaspora spp.) and Saccharomyces spp. in fresh wine must, during fermentation and in the finished wine. The specificity of all primer couples for their target yeast species were validated and the QPCR methods developed were compared with a classic approach of colony identification by RFLP-ITS-PCR on cultured samples. Once the methods had been developed and validated, they were used to study these non-Saccharomyces yeasts in wine samples and to monitor their dynamics throughout the fermentation process. This study confirms the usefulness and the relevance of QPCR for studying non-Saccharomyces yeasts in the complex yeast ecosystem of grape must and wine.

Brettanomyces bruxellensis evolution and volatile phenols production in red wines during storage in bottles

AIMS

The presence of Brettanomyces bruxellensis is an important issue during winemaking because of its volatile phenols production capacities. The aim of this study is to provide information on the ability of residual B. bruxellensis populations to multiply and spoil finished wines during storage in bottles.

METHODS AND RESULTS

Several finished wines were studied. Brettanomyces bruxellensis populations were monitored during two and a half months, and volatile phenols as well as chemical parameters regularly determined. Variable growth and volatile phenols synthesis capacities were evidenced, in particularly when cells are in a noncultivable state. In addition, the volatile phenol production was clearly shown to be a two-step procedure that could strongly be correlated to the physiological state of the yeast population.

CONCLUSIONS

This study underlines the importance of minimizing B. bruxellensis populations at the end of wine ageing to reduce volatile phenols production risk once the wine in bottle. Moreover, the physiological state of the yeast seems to have an important impact on ethyl-phenols production, hence demonstrating the importance of taking into account this parameter when analysing wine spoilage risks.

SIGNIFICANCE AND IMPACT OF THE STUDY

Little data exist about the survival of B. bruxellensis once the wine in bottle. This study provides information on the alteration risks encountered during wine storage in bottle and reveals the importance of carrying on further studies to increase the knowledge on B. bruxellensis physiology.

Influence of carbon source and surface hydrophobicity on the aggregation of the yeastKluyveromyces bulgaricus

Aggregation of the yeast Kluyveromyces bulgaricus is mediated by the galactose-specific lectin KbCWL1. This lectin contains hydrophobic amino acids and its activity is calcium dependent. A specific fluorescent probe, 1-anilinonaphthalene-8-sulfonic acid in the free acid form (ANS; Sigma Chemical Co., St. Louis, Missouri), was used to study the hydrophobic areas on the cellular surface of K. bulgaricus. Changes in surface hydrophobicity during the growth and aggregation of yeast cells were studied. Surface hydrophobicity increased during growth and depended on the amount of yeast cells in the culture medium. During growth, the size of the hydrophobic areas on the cell surface was measured using ANS and was found to increase with the percentage of flocculating yeasts. Our results strongly suggest that the hydrophobic areas of the cell walls of yeast cells are involved in the aggregation of K. bulgaricus.Key words: aggregation, carbon source, fluorescence probe, hydrophobicity, yeast.

Augmentation de la concentration plasmatique de la protéine C-réactive dans le diabète de l’enfant et de l’adulte jeune

OBJECTIVE

To investigate whether high sensitivity C-reactive protein (hs CRP) levels are elevated in young type 1 diabetic patients and to determine the relationships with age, degree of metabolic control determined by glycated hemoglobin (HbA1c), blood lipids, and subclinical complications.

METHODS

High sensitivity CRP was determined in young type 1 diabetic patients and in healthy controls. Blood lipids and HbA1c were also determined. The patients were divided into 2 groups. In group A, patients were free from subclinical complications (retinopathy, nephropathy and neuropathy) and in group B, patients had at least one subclinical complication.

RESULTS

The hs CRP concentrations were significantly higher in the 126 diabetic patients (55 girls and 71 boys) than in the 52 controls (2.6+/-4mg/L vs 0.7+/-0.7mg/L; p<0.001). This difference persisted when comparing the normal subjects with the 81 patients of group A (2.0+/-3.1mg/L; p<0.01) and the 45 patients of group B (3.6+/-5.1mg/L; p<0.001). The hs CRP concentrations were significantly correlated with total cholesterol, total cholesterol/HDL-cholesterol ratio, and LDL cholesterol for the 2 groups of patients. In the patients of group A, significant correlations were observed between hs CRP and age or duration of diabetes. No correlation was observed between hs CRP levels and glycaemia, HbA1c and HDL-cholesterol in the two groups of patients.

CONCLUSION

Levels of hs CRP were 3-fold greater in diabetic patients without complications than in controls and 5-fold greater in diabetic patients with subclinical complications. High sensitive CRP therefore appears to be an interesting indicator of the risk for developing complications.

Study on agglutinating factors from flocculent Saccharomyces cerevisiae strains

The lectin-like theory suggest that yeast flocculation is mediated by an aggregating lectinic factor. In this study we isolated an agglutinating factor, which corresponds to lectin, from whole cells by treating the flocculent wild-type Saccharomyces cerevisiae NCYC 625 strain and its weakly flocculent mutant [rho degrees ] with EDTA and two non-ionic surfactants (Hecameg and HTAC). The dialysed crude extracts obtained in this way agglutinated erythrocytes and this hemagglutination was specifically inhibited by mannose and mannose derivatives. However, SDS-PAGE profiles showed that the three reagents had different effects on the yeast cells. The non-ionic surfactants appeared to be the most efficient, as their extracts possessed the highest specific agglutinating activity. The products released by the wild-type strain presented a higher specific agglutinating activity than those released by the [rho degrees ] mutant. Purification of the agglutinating factor from extracts of both strains by affinity chromatography revealed two active bands of relative mass of 26 and 47 kDa on SDS-PAGE. Mass spectrometry analysis by MALDI-TOF, identified a 26 kDa band as the triose phosphate isomerase (TPI) whereas a 47 kDa band was identical to enolase. Edman degradation showed that the N-terminal sequences of these proteins were similar to TPI and enolase, respectively. The difference in the flocculation behaviour of the two strains is due to changes in the protein composition of the cell wall and in the protein structure involved in cell-cell recognition.

Variation in survival rates for the alpine marmot (Marmota marmota): effects of sex, age, year, and climatic factors

We examined variation in annual survival rates in a population of alpine marmots (Marmota marmota) according to intrinsic (sex and age) and extrinsic (year and climate) factors. We tested predictions concerning (i) a sex effect in a monogamous non-dimorphic species, (ii) age structure of survival rates in a mesomammal, and (iii) the annual variability effect and the contribution of stochastic climatic factors, especially snow cover, frost, and rainfall. We used a 8-year dataset of 367 marmots that were livetrapped and marked in La Sassière Nature Reserve in the French Alps between 1990 and 1997. Survival and recapture rates were modelled using recent developments in capture–recapture models. Sex had no effect on survival rates, which agrees with the predictions of sexual selection. Survival rates for young of the year (YOY, from weaning to first birthday) were, on average, lower than in the older age class. In the older age class, annual variation occurred that was strongly related to the intensity of autumn frost. By determining the soil temperature at the beginning of hibernation, this factor, though short-lived, could have determined the energetic cost of hibernation. Neither annual variation nor an environmental effect was detected in YOY despite a large sample size. Social thermoregulation could contribute to the stability of YOY survival rates. As infanticide was common after the immigration of a new dominant male, survival of YOY seemed to depend more on social events than on stochastic climatic ones.

Sterol and fatty acid composition of Candida lusitaniae clinical isolates

The sterol and fatty acid compositions of four amphotericin B-resistant and of two amphotericin B-susceptible Candida lusitaniae clinical isolates were determined. A flow cytofluorometric susceptibility test (FCST) with a membrane potential-sensitive cationic dye was used as a complement to the conventional method for selecting the isolates. Compared to susceptible isolates, resistant ones showed a greatly reduced ergosterol content and changes in sterol composition, consistent with a defect in Delta8-->7 isomerase. Within each group, no correlation between the sterol or fatty acid pattern or composition and both the degree of in vitro susceptibility and FCST MIC was found.

Isolation and biochemical characterization of cell wall tight protein complex involved in self-flocculation of Kluyveromyces bulgaricus

Flocculation of yeasts is a cell-cell aggregation phenomenon which is driven by interactions between cell wall lectins and cell wall heteropolysaccharides. In Sabouraud medium, Kluyveromyces bulgaricus was highly flocculent. Incubation of flocculent K. bulgaricus cells with EDTA or Hecameg led to extracts showing hemagglutinating and flocculating properties. Purification of the extracts by native PAGE gave two bands which allowed flocculation of deflocculated K. bulgaricus. Both bands with specific reflocculating activity were composed of five subunits, of which only three possessed weak reflocculating activity upon deflocculated yeast. The mixture of these three proteins allow the recovery of initial specific reflocculating activity of the complex. These three proteins, denoted p28, p36 and p48, presented, in their first 15 amino acids, homologies with glycolysis enzymes, i.e., 3-phosphoglycerate mutase, glyceraldehyde-3-phosphate dehydrogenase and enolase, respectively. However, no such enzymatic activity could be detected in the crude extract issued from treatment with EDTA and Hecameg of flocculent yeast cells. When yeasts had grown in glucose poor medium, flocculation was drastically affected. The EDTA and Hecameg crude extracts showed weak reflocculating activity. After PAGE, the protein complexes did not appear in the EDTA extract, but they did appear in the Hecameg crude extract. These results suggest that: (i) self-flocculation of K. bulgaricus depends on the expression of different floc-forming protein complex, (ii) these proteins are galactose specific lectins showing homologies in their primary structure with glycolysis enzymes.

The role of glucose in the Kluyveromyces bulgaricus flocculation phenomenon: transduction by cAMP-dependent protein kinase pathway?

Yeast flocculation appears to be dependent on several culture conditions such as nitrogen or carbon sources. In 0.2% glucose medium Kluyveromyces bulgaricus flocculation intensity is weak (10% at maximum) by comparison with flocculation in 2% glucose medium (85% maximum). Addition of glucose to K. bulgaricus in exponential growth phase in 0.2% glucose medium produced a rapid increase of the flocculation percentage during the 30 min following the addition of glucose. cAMP and 2,4-dinitrophenol showed similar effects while cAMP-dependent protein kinase (PKA) inhibitors exhibited an antagonist effect. Moreover, the induction of flocculation did not seem to imply translation of new proteins: cycloheximide had no effect, although growth was inhibited. The induction of flocculation mainly implies ATP hydrolysis for activation or secretion of galactose-specific receptors as demonstrated by treatment with NaN(3). We propose a hypothesis that involves a PKA transduction signal leading to flocculation.

Solid-phase microextraction of volatile components from natural grassland plants

The volatile components from nine plants growing on natural grasslands in Auvergne, central France, selected for the broad qualitative and quantitative diversity of their terpenoid fractions, were analyzed by high-resolution gas-phase chromatography and mass spectrometry (HRGC-MS) after static headspace solid-phase microextraction (SHS-SPME). SHS-SPME allowed all the plant material to be analyzed under the same conditions despite its wide-ranging composition. This is not always possible with other extraction methods. Using an apolar poly(dimethylsiloxane) (PDMS) phase, numerous terpenoid hydrocarbons, together with alcohols, cyclic ethers, and esters, were extracted. Its ease of use and the high resolution of the chromatographic profiles obtained make SHS-SPME well suited to the rapid characterization of the main components of the volatile fraction of plants. Of the nine plants studied, four (Meum athamanticum, Pimpinella saxifraga, Achillea millefolium, and Thymus pulegioides) exhaled more than 60 different volatile components. Certain terpenes present in large amounts in these plants might help link dairy products to grazing pasture, thus improving food traceability.

Amphotericin B resistance and membrane fluidity in Kluyveromyces lactis strains

The membrane fluidity of reduced-amphotericin B (AmB)-sensitivity Kluyveromyces lactis mutant strain is higher than that of the wild-type K. lactis strain. After culture of the K. lactis and K. lactis mutant cells in the presence of subinhibitory doses of AmB (10 and 125 mg/liter, respectively), the plasma membranes of both yeast strains also showed a higher fluidity than did those of control cells. High membrane fluidity was associated with changes in the structural properties of the membranes. Culture of the K. lactis and K. lactis mutant cells in the presence of AmB induced changes in membrane lipid contents. In particular, phospholipid contents were increased in both strains treated with AmB, compared with their corresponding counterparts. As a result, the sterol/phospholipid ratio decreased. The relative proportion of monounsaturated fatty acids also increased after AmB treatment. The saturated fatty acid/monounsaturated fatty acid ratio decreased in K. lactis and K. lactis mutant cells treated with AmB but also in K. lactis mutant control cells compared to that in the K. lactis wild strain. These changes in lipid composition explain the higher fluidity, which could represent a process of metabolic resistance of the yeasts to AmB.

Permeability of yeast cell envelope to fluorescent galactosylated telomers derived from THAM

The work reported herein deals with the study of cellular recognition and permeability phenomena in yeasts. Various galactosylated organic telomers derived from trishydroxymethyl-aminomethane (THAM) and bearing fluorescent moieties were synthesized in order to measure their ability to cross the yeast cell envelope. Grafting fluorescent probes on the organic telomer backbone allowed us to study their specific behaviors toward the yeasts by fluorescence microscopy. Yeasts belonging to the genera Kluyveromyces and Saccharomyces were used for this study. With Saccharomyces yeast cells bearing mannose-specific lectins or lectin-like proteins, on their outer surface, all the galactosylated or nongalactosylated organic telomers passed through the cell envelope and invaded the cytoplasm. With Kluyveromyces yeast cells bearing galactose-specific lectins, the galactosylated organic telomers were blocked at the outer surface while the nongalactosylated derivatives crossed the cell envelope. Moreover, preincubation of Kluyveromyces yeasts with galactose or methylgalactose inhibited the cell surface anchorage of the organic telomers and allowed their penetration into the cytoplasm. When assays were performed on spheroplasts of both Kluyveromyces and Saccharomyces yeasts, no fixation on the surface could be observed, and all the derivatives went through the membrane and invaded the cytoplasm.

Evidence for a lectin in Kluyveromyces sp. that is involved in co-flocculation with Schizosaccharomyces pombe

Co-flocculation is the aggregation of yeasts belonging to different genera or species. Kluyveromyces bulgaricus and Kluyveromyces lactis 5c are self-flocculent, but they can also co-flocculate with the non-flocculent yeast Schizosaccharomyces pombe 972 h(-). This co-flocculation is inhibited by D-galactose and galactose derivatives and involves the binding of a galactose-specific proteinic receptor (or lectin) of Kluyveromyces sp. to the cell wall galactomannans of S. pombe. The proteinic receptor is strongly anchored in the cell wall, it was partially purified by affinity chromatography using immobilized S. pombe galactomannans. This galactose-specific proteinic receptor does not appear to interfere in K. bulgaricus or K. lactis self-flocculation, which is mediated by another galactose-specific lectin weakly linked at the cell wall.

Mitochondrial function in cell wall glycoprotein synthesis in Saccharomyces cerevisiae NCYC 625 (Wild type) and [rho(0)] mutants

We studied phosphopeptidomannans (PPMs) of two Saccharomyces cerevisiae NCYC 625 strains (S. diastaticus): a wild type strain grown aerobically, anaerobically, and in the presence of antimycin and a [rho(0)] mutant grown aerobically and anaerobically. The aerobic wild-type cultures were highly flocculent, but all others were weakly flocculent. Ligands implicated in flocculation of mutants or antimycin-treated cells were not aggregated as much by concanavalin A as were those of the wild type. The [rho(0)] mutants and antimycin-treated cells differ from the wild type in PPM composition and invertase, acid phosphatase, and glucoamylase activities. PPMs extracted from different cells differ in the protein but not in the glycosidic moiety. The PPMs were less stable in mitochondrion-deficient cells than in wild-type cells grown aerobically, and this difference may be attributable to defective mitochondrial function during cell wall synthesis. The reduced flocculation of cells grown in the presence of antimycin, under anaerobiosis, or carrying a [rho(0)] mutation may be the consequence of alterations of PPM structures which are the ligands of lectins, both involved in this cell-cell recognition phenomenon. These respiratory chain alterations also affect peripheral, biologically active glycoproteins such as extracellular enzymes and peripheral PPMs.

Molecular identification of Lactobacillus hilgardii and genetic relatedness with Lactobacillus brevis

Conventional phenotypic methods lead to misidentification of the lactic acid bacteria Lactobacillus hilgardii and Lactobacillus brevis. Random amplified polymorphic DNA (RAPD) and repetitive element PCR (REP-PCR) techniques were developed for a molecular study of these two species. The taxonomic relationships were confirmed by analysis of the ribosomal operon. Amplified DNA fragments were chosen to isolate L. hilgardii-specific probes. In addition to rapid molecular methods for identification of L. hilgardii, these results convincingly proved that some strains first identified as L. brevis must be reclassified as L. hilgardii. The data clearly showed that these molecular methods are more efficient than phenotypic or biochemical studies for bacterial identification at the species level.

Neurogenesis during caudal spinal cord regeneration in adult newts

After tail amputation in urodele amphibians, dramatic changes appear in the spinal cord rostral to the amputation level. Transection induces a proliferation response in cells lining the ependymal canal, giving rise to an ependymal tube in which neurogenesis occurs. Using the thymidine analog bromodeoxyuridine (BrdU) in short- and long-term labeling of cells undergoing DNA synthesis (S phase of the cell cycle), specific cell markers, and cell cultures, we show that neurons derive from the proliferative ependymal layer of the ependymal tube.

Cell targeting by glycosidic telomers. Specific recognition of the Kb CWL1 lectin by galactosylated telomers

This work deals with the synthesis and lectinic recognition ability of galactosylated telomers. To investigate if telomeric carriers could exhibit cellular recognition properties, we have synthesized mono- and polygalactosylated tris(hydroxymethyl)acrylamidomethane (THAM) telomers. The affinity of such macromolecular drug carriers toward a receptor, the yeast Kb CWL1 lectin, was defined, and the influence of mono- or polygalactosylation of THAM units on the recognition phenomenon was assessed. The lectinic affinity of the compounds was estimated by measuring the inhibition of yeast aggregation. The average degree of polymerization as well as the hydrophilic-lipophilic balance of such galactosylated telomers affects their recognition ability for the lectin.

Implication of cell wall constituents in the sensitivity of Kluyveromyces lactis strains to amphotericin B

In Kluyveromyces lactis, the cell wall compositions of Kl (ATCC 96897), a wild sensitive strain, and Klm (ATCC 96896), a strain resistant to amphotericin B (AmB), were shown to be very different, since the walls in the latter were significantly enriched in hexosamine, but had a reduced content in phosphate and amino acid. In both strains, the cell walls limited their sensitivity to this antifungal agent. The absence of cell wall increased the sensitivity of the cells to this polyene by 5 to 10-fold. When the cells were treated with enzymes such as pronase and chitinase in order to change the cell wall structure just before inoculation, the yeasts appeared more resistant to the antibiotic. However, treatments with chymopapain and phospholipase C did not significantly change the sensitivity of the two strains to this agent. Cells treated with acid phosphatase displayed a longer lag phase than the control cells. In addition, when cultured in the presence of AmB, the cells were less sensitive to this agent. The present results reveal that both a change in the ionic charges of the cell wall and an alteration in the cell wall structure modified the sensitivity of these yeast strains to AmB.

Comparative extraction procedures for a galactose-specific lectin involved in flocculation of Kluyveromyces lactis strains

The extraction of a lectinic factor involved in yeast flocculation, from two Kluyveromyces lactis strains (a flocculent K. lactis 5c and a non-flocculent K. lactis 5a strain) was performed using EDTA and two surfactants, Hecameg and HTAC. The properties of the different extracts were tested by haemagglutination and reflocculation of deflocculated K. lactis 5c cells. Hecameg gave the highest yields of active lectinic extract but the extraction with EDTA seemed more specific. HTAC extracts showed a very low activity. The possibilities of extraction of the agglutinating factor, either by an ion chelator or by surfactants, suggest that this factor may be anchored in the cell envelope, i.e. the cell wall and the membrane, by different mechanisms. All the assays revealed a galactose-specific lectinic activity was present that in the flocculent as well as in the non-flocculent strain. This indicates that the absence of flocculation with K. lactis 5a is mainly due to a defect in the ligands of the lectin rather than to a loss of the lectinic factor itself.

Neural crest-like cells originate from the spinal cord during tail regeneration in adult amphibian urodeles

Using in vitro cell-marking experiments and transplantation in tail regenerates, we have recently shown (Benraiss et al., 1996) that clonal cells derived from adult newt spinal cord (SC) cultures could find suitable cues in blastemal mesenchyme to enable them to differentiate into melanocytes or Schwann cells. This led to the question of whether neural crest-like cell derivatives might emerge from the ependymal tube as tail regeneration proceeded. To address this question we used the biolistic method for in situ transfection of caudal SC cells. These cells were transfected with an alkaline phosphatase marker gene. The potentialities of transfected cell derivatives in tail regenerates were analyzed using histochemistry or immunohistochemistry. As early as eight days after transfection, labeled cells were detected in the regenerating SC and around its "terminal vesicle" (TV). Two to four weeks following transfection, most of the labeled cell derivatives could be identified either by dark granules as melanocytes or by galactocerebroside staining as Schwann cells. Electron microscopic investigations revealed the incompletely organized cytoarchitecture of the TV, suggesting that an exit of cells was possible at this level, at least from its "open" dorsal part. Furthermore, the localization of ciliated cells in the blastemal mesenchyme, especially around the TV, supported this view by suggesting that they might be ependymal cells detached from it. Our findings therefore led us to believe that in the newt, during tail regeneration, neural crest-like cells emerging from the TV could participate in the formation of the peripheral nervous system, especially by providing Schwann cells and melanocytes.

The function of type IV collagen during Drosophila muscle development

Type IV collagen forms a network that provides the major structural support for basement membranes. Basement membranes are specialized forms of extracellular matrix with important functions in development. One collagen gene (Dcg1) was characterized in Drosophila melanogaster and shown to encode a collagen chain related to vertebrate basement membrane type IV collagen chains. Therefore, to access the functional importance of type IV collagen during Drosophila myogenesis, we adopted two different approaches to decrease the Dcg1 gene expression in Drosophila embryos. We describe, here, that the decrease in Dcg1 gene expression causes, in particular, defective muscle attachments. These mutant phenotypes suggest that type IV collagen acts to stabilize cell-matrix interactions.

[Immigration of a pregnant female in an alpine marmot family group: behavioural and genetic data]

The acceptance of a pregnant female by the dominant male of a family group of alpine marmots (Marmota marmota) (population of La Grande Sassière, Parc national de la Vanoise, French Alps) was revealed by the combined results from microsatellite polymorphism analysis and behavioural studies. These first results seem to indicate that the mating system of the alpine marmot is more complex than previously thought, that polygyny cannot be excluded, and that adult females can join neighbouring groups. This acceptance would have been interpreted as an extra-pair fertilization if complete field data had not been available.

Clonal cell cultures from adult spinal cord of the amphibian urodele Pleurodeles waltl to study the identity and potentialities of cells during tail regeneration

The urodele amphibians are nearly the only adult vertebrates able to regenerate their missing or amputated tail. The most striking feature of this model lies in the ability of the spinal cord (SC) to differentiate, within the regenerating tail, a new ependymal tube from which the SC and the peripheral nervous system originate. A fundamental question is whether, in response to tail excision, the ependymoglia of the old SC stump behaves as an embryonic neuroepithelium. To evaluate this possibility, cell lines from primary cell cultures of adult SC were established for the first time in newts, and two cell clones, immunochemically characterized as ependymoglial cell populations, could be obtained. To analyze the potentialities of these clonal cells, after transplantation in tail regenerates, cell-marking experiments, using either in vitro transfection with lacZ gene or the lineage tracer lysinated rhodamine dextran (LRD), were performed. One to 2 weeks postimplantation, most of labeled derivatives were identified as melanocytes. Interestingly, labeled cells were also seen integrated in the ependymoglia of the regenerating SC. Two to 6 weeks after implantation in young regenerates, we also observed LRD-labeled elongated cells close to nerves or myofibers which were unambiguously identified as Schwann cells by galactocerebroside staining. Taken together, these findings showed that clonal cells derived from adult newt SC cultures could largely find, in regenerate mesenchyme, suitable environmental conditions to differentiate into melanocytes or Schwann cells. Because these two cells types arise from neural crest cells during embryo-genesis, this supports the interesting view that multipotent cells are still present in the SC of adult urodeles.

Identification of 24-methylene-24,25-dihydrolanosterol as a precursor of ergosterol in the yeasts Schizosaccharomyces pombe and Schizosaccharomyces octosporus

Study of the plasma membrane sterol composition in the yeasts Schizosaccharomyces pombe and Schizosaccharomyces octosporus revealed the presence of ergosterol, lanosterol, dehydroergosterol, fecosterol, episterol and 24-methylene-24,25-dihydrolanosterol (eburicol), a C-31 derivative. The growth of both yeasts in the presence of ketoconazole led to a decrease by 85% of the ergosterol content while the levels of lanosterol and eburicol increased. This suggests that in the biosynthetic pathway of ergosterol in Schizosaccharomyces species, the transmethylation process on the C-24 may occur directly on lanosterol and not only on zymosterol. On the other hand, it cannot be excluded that in the genus Schizosaccharomyces two routes exist from lanosterol to ergosterol: the classical one via a direct C-14, C-4 demethylation of lanosterol and the second one via the formation of a C-31 derivative followed by demethylations.

Changes in cell wall composition of deformed ras1- cells of Schizosaccharomyces pombe

Disruption of the Schizosaccharomyces pombe ras1 gene results in a morphological transformation to large spheres, in contrast to wild-type cells which grow as rods. Chemical analysis of isolated cell walls showed no significant changes in saccharide content but an increase in protein and phosphate contents in ras1- walls relative to parent walls. Polymers tightly bound to the cell wall were solubilized by SDS treatment. Several compounds with molar mass ranging from 22 to 130 kDa and more were resolved by gel filtration and SDS-PAGE. Among low-molar-mass species, a component moving as a band at 31 kDa was conspicuous in ras1- cell walls. It was solubilized by heating in Tris-HCl buffer and shown to have a beta-1,3-glucanase activity against laminarin. The level of the enzyme was by 30% higher in the ras1- cell wall than in the wild-type cell wall. This enzyme may participate in the remodelling of the rigid glucan network and account (at least partially) for the aberrant cell shape. The ras1- cell wall contained a high level of charged polymers, especially phosphoproteins, raising the appealing possibility that ras1- is involved in a putative kinase cascade required to sense and respond to external stimuli destined for the cell wall. Although the present study shows that ras1 loss of function and altered cell wall composition are closely linked defects, it has still to be shown that the ras1 protein is directly involved in alterations found in the mutant cell walls.

Tenascin expression in developing, adult and regenerating caudal spinal cord in the urodele amphibians

Tenascin (Tn) protein and transcripts were analyzed in developing, adult and regenerating caudal spinal cord (SC) of Pleurodeles waltl. A polyclonal antibody (PAb) against Xenopus Tn and a newt Tn cDNA probe were used. In Western blots, anti-Tn PAb recognized Tn polypeptides of 200-220 kDa in tail regenerate extracts, but also the homolog of Tn/Cytotactin/J1 in brain and SC of adult newt. Immunofluorescence studies showed some reactivity around ependymoglial cells and strong labeling in the nervous tracts, in the developing as well as in the regenerating SC or adult SC. Immunogold electron microscopy revealed the presence of Tn throughout the ependymoglial cells, particularly near and along the plasma membrane of radial processes surrounding axons, especially growth cones. Tn could be more precisely found within rough endoplasmic reticulum and Golgi structures, or again in the surrounding extracellular space. This suggested that Tn was at least produced by radial glial profiles forming axonal compartments in which axons grew. Using the DNA probe for Tn, expression of Tn mRNA was also examined by Northern blot and RNAase protection analyses and by in situ hybridization, respectively. The levels of transcripts, barely detectable in adult tail, increased in regenerates from 3 days through 4-8 weeks post-amputation. In situ Tn mRNA were mainly localized in the mesenchyme, especially at the epithelial-mesenchymal interface, and in the developing cartilage, at the early regeneration stages, whereas high amounts of transcripts were seen not only at these stages, but also later, in the regenerating SC. Our main results supported the view that, in the caudal SC of newts, Tn, synthesized by radial ependymoglial cells, was similarly expressed during regeneration as well as larval development, and exhibited a sustained high accumulation level in the adult SC. On the basis of the multifunctional properties of Tn, the putative roles played by Tn as a substrate for neuronal pathfinding and boundary shaping were discussed.

Membrane phospholipid composition in Saccharomyces uvarum cells grown in the presence of subinhibitory doses of amphotericin B and desertomycin

In Saccharomyces uvarum cultures, subinhibitory doses of amphotericin B and desertomycin induced alterations in the plasma membrane phospholipid composition. Amphotericin B increased the lipid content in the plasma membrane. It showed a pronounced effect on fatty acyl constituents by raising the amounts of mono- and polyunsaturated derivatives in phospholipids. On the other hand, desertomycin had no apparent effect on fatty acid synthesis but altered the relative composition of phospholipids in the membrane. Phosphatidyl choline and phosphatidyl ethanolamine contents decreased, while their precursors, phosphatidyl serine and phosphatidic acid, increased. On the other hand, the rates of phosphatidyl inositol were not significantly affected by the action of either antifungal agent.

Formation of the extracellular matrix during the epimorphic anterior regeneration of Owenia fusiformis: autoradiographical and in situ hybridization studies

During post-traumatic regeneration of the polychaete annelid Owenia fusiformis, the extracellular matrix (ECM) formation was studied by light and electron microscopy and by histoautoradiography after incorporation of tritiated proline as marker for collagenic proteins. Three days after amputation, a new basement membrane was reformed in the blastema between the ectoderm and the mesoderm. At the same time, the cytoskeleton and the anchoring structures (hemidesmosomes) were differentiated in the basal part of the ectodermal cells. Four days after amputation, collagen fibers appeared in the extracellular matrix newly reformed between the ectodermal and mesodermal layers. The existence of a proximo-distal gradient in the organization of the new extracellular matrix and the accumulation of molecules labeled by 3H-proline was shown. This accumulation started at the level of the injured segment of the stump. Differences in labeling intensity were seen in the regenerate. Within specific organogenetic zones, i.e. the epidermal gland analagen, the branchial buds and the stomodeal invagination, the labeling between the ectodermal and mesodermal layers was less intense than in other parts of the regenerate. In the mesodermal connective septa (dissepiments), located between consecutive segments, the labeling and the accumulation of extracellular material occurred later than the formation of the ectodermal basement membrane. In situ hybridization of a DNA molecular probe corresponding partially to the coding region of the collagen-like gene Ocg8, showed a spatio-temporal expression of this gene. Northern blot analysis showed a single transcript of 6.6 kb. Four days after amputation the accumulation of this transcript was exclusively localized at the level of the ectodermal layer during differentiation of the regenerate. The ectoderm was thus shown to play a dynamic role during the first stages of traumatic regeneration, although it did not seem to be directly involved in the early events of the metameric process.