Sensing of DNA non-homology lowers the initiation of meiotic recombination in yeast

BACKGROUND

Meiotic recombination between homologous chromosomes in the yeast Saccharomyces cerevisiae is initiated by the formation of DNA double-strand breaks (DSBs). The mechanism of DSB formation and the factors that determine their frequency and location have yet to be elucidated. Current studies of meiotic recombination are also concerned with the question of the functional relationship between DSB formation and the other meiotic processes of homology searching, pairing and synapsis of homologues.

RESULTS

To test if DNA identity is required for high levels of DSBs and recombination, we have asked whether small DNA heterologies (140-547 bp) located within the well characterized ARG4 initiator of meiotic recombination, can affect DSB formation and gene conversion events in the ARG4 locus. The present physical and genetic analyses show that some heterologies reduced recombination frequencies without altering DSB formation, whereas others reduced both DSB and gene conversion frequencies.

CONCLUSIONS

These results suggest that DNA heterologies overlapping a recombination initiator impair meiotic gene conversion at two levels. First, some heterologies affect the level of DSB formation, revealing the existence of an anti-initiation process sensing the presence of sequence non-homology between the homologous chromosomes. Second, heterologies can impair the successful processing of the recombination intermediates once DSBs are made. We present a model for interhomologue cross-talks involving chromosomal and DNA/DNA interactions.

Endo.SK1: an inducible site-specific endonuclease from yeast mitochondria

Site-specific endonucleases have been found in various eukaryotic organelles such as mitochondria, chloroplasts and nuclei. These endonucleases initiate site-specific or homologous gene conversion in mitochondrial and nuclear DNA. Here, we report a new site-specific endonuclease activity, Endo.SK1, identified in mitochondria of strain SK1, a homothallic diploid strain of Saccharomyces cerevisiae. Nucleotide sequences around the Endo.SK1-cleavage sites are different from those of known yeast site-specific endonucleases. The Endo.SK1 activity is, at least partly, specified by a gene in the SK1-derived mitochondria. A novel feature of the Endo.SK1 activity is its inducibility: the endonuclease activity was induced by ca. 40-fold by transfer of cells from a glucose medium into an acetate medium, and was then repressed. This transient induction was independent of the ploidy level of the cells, and coincided with induction of fumarase, a mitochondrial enzyme involved in the TCA cycle. Co-induction and co-repression of the mitochondrial site-specific endonuclease activity and a respiration-related enzyme indicate that the endonuclease activity in regulated in response to physiological conditions, and suggest a possible role for the endonuclease in mitochondrial DNA metabolism.

Contribution of cutinase serine 42 side chain to the stabilization of the oxyanion transition state

Cutinase from the fungus Fusarium solani pisi is a lipolytic enzyme able to hydrolyze both aggregated and soluble substrates. It therefore provides a powerful tool for probing the mechanisms underlying lipid hydrolysis. Lipolytic enzymes have a catalytic machinery similar to those present in serine proteinases. It is characterized by the triad Ser, His, and Asp (Glu) residues, by an oxyanion binding site that stabilizes the transition state via hydrogen bonds with two main chain amide groups, and possibly by other determinants. It has been suggested on the basis of a covalently bond inhibitor that the cutinase oxyanion hole may consist not only of two main chain amide groups but also of the Ser42 O gamma side chain. Among the esterases and the serine and the cysteine proteases, only Streptomyces scabies esterase, subtilisin, and papain, respectively, have a side chain residue which is involved in the oxyanion hole formation. The position of the cutinase Ser42 side chain is structurally conserved in Rhizomucor miehei lipase with Ser82 O gamma, in Rhizopus delemar lipase with Thr83 O gamma 1, and in Candida antartica B lipase with Thr40 O gamma 1. To evaluate the increase in the tetrahedral intermediate stability provided by Ser42 O gamma, we mutated Ser42 into Ala. Furthermore, since the proper orientation of Ser42 O gamma is directed by Asn84, we mutated Asn84 into Ala, Leu, Asp, and Trp, respectively, to investigate the contribution of this indirect interaction to the stabilization of the oxyanion hole. The S42A mutation resulted in a drastic decrease in the activity (450-fold) without significantly perturbing the three-dimensional structure. The N84A and N84L mutations had milder kinetic effects and did not disrupt the structure of the active site, whereas the N84W and N84D mutations abolished the enzymatic activity due to drastic steric and electrostatic effects, respectively.

[Method selected for the determination of creatinine in plasma or serum. Choice of optimal conditions of measurement]

The method selected by the SFBC (Société française de biologie clinique) is derived from the colorimetric reaction of creatinine with alkaline picrate, measured kinetically, without any pretreatment step. The key parameters of the reaction determining the quality of the results are studied, with special regard to samples including known interferents. The aims of the study were to gain an optimal analytical sensitivity and to reduce main interferences (acetoacetate, bilirubine, glucose, protein) which plague the Jaffé reaction, through a comprehensive study of the reagents, of their concentrations and of the analytical procedures. The selected concentrations (in the test) are: 150 mmol/L sodium hydroxide, 10 mmol/L picric acid and 2 g/L sodium dodecyl sulfate. Ten millilitres of a BRIJ solution (30% volvol) are added to the reagent. The operating procedures are as follow: sample ratio 0.07 to 0.08; wavelength 505 to 510 nm; temperature 37 degrees C; incubation of the specimen with the alkaline reagent 5 mn (at least), before starting the reaction with picric acid. A seric calibrator is recommended. The first measurement is taken 20 to 40 s after starting the reaction. Total measurement time is 120 to 150 seconds.

[Validation and study of the transferability of the selected technique by SFBC for the determination of creatinine in plasma]

A selected method for the determination of creatinine in plasma, using the reaction with alkaline picrate without prior pretreatment has been proposed by the Commission 'Validation de techniques' in the SFBC (Société Française de biologie clinique). The transferability step was conducted in seven laboratories, equipped with different automatic analyzers, using analytical procedures derived from the recommended method. Its goal was to test whether the original analytical performances could be maintained and consistent results obtained. The validation step was designed to evaluate the linearity limits of the analytical range, the detection limit, to assess accuracy as compared to a high performance liquid chromatography and to investigate the effect of the main interferents. Linearity limits are 15 and 2000 mumol/L. The detection limit is 3 to 8 mumol/L according to the analytical systems. The selected method can fulfil the set imprecision goals: intralaboratory CV minus than 2% (within-run), minus than 4% (run-to-run), interlaboratory CV minus than 5% (for 100 mumol/L creatinine). Inaccuracy evaluated for the chosen control sera is 1 to 15% as compared to the chromatographic method, according to the sera and to the analytical systems. The results obtained with the selected method are more consistent with the HPLC than are those obtained with an alkaline picrate method without SDS or with an enzymatic method. No interference could be demonstrated for acetoacetate (up to 8 mmol/L), hemoglobin (up to 210 mumol/L), unconjugated bilirubin (up to 250 mumol/L), glucose (up to 30 mmol/L), IgG (up to 45 g/L), albumin (up to 60 g/L). The effect of cephalosporins depends on the molecule. The reagents are stable for at least 6 months when stored in closed vials at +20 degrees C. The alkaline reagent is stable 30 days at +4 degrees C. Reference limits (0.025 and 0.975 fractiles) have been established for healthy adults. They are respectively 73 to 126 mumol/L for men and 59 to 100 mumol/L for females.

Implementation of napping in industry and the problem of sleep inertia

It seems reasonable to believe that in specific situations napping at the work place would be possible and used if authorized and encouraged. Very short naps could have very positive long-term effects on biological functions. Training someone to sleep for short periods appears feasible if there is a high motivation to do so. Sleep inertia can be considered as one of the main limiting factors in napping strategy. Sleep inertia depends on different factors such as sleep stage preceding the awakening, temporal placement of the nap, duration of nap and wakefulness preceding it, etc. The effects of sleep inertia might be different depending on the type of task, and a reactivation technique applied immediately after awakening may remove it. Despite the fact that its implementation in industry raises some practical issues, napping can be considered as a possible strategy to increase the vigilance level of night workers.

Intracellular concentrations of fura-2 and fura-2/am in vascular smooth muscle cells following perfusion loading of fura-2/am in arterial segments

A new method for the determination of tissue concentrations of Fura-2 and Fura-2/AM was developed based upon acetonitrile extraction followed by RP-HPLC separation (using tetrahexylammonium as counter-ion), post-column alkaline hydrolysis of Fura-2/AM, and fluorimetric detection. The detection limit was 1.2 nM and 1 nM for Fura-2 and Fura-2/AM, respectively. When this technique was applied to perfusion-loaded segments of the rat tail artery, intracellular concentrations of Fura-2 determined by tissue disruption were 10 times those obtained by comparing the increase in fluorescence at the isoemissive point (following loading), with a calibration curve for Fura-2. Loading conditions of 90 min at [Fura-2/AM]e = 5 microM were optimal in terms of [Fura-2]i which attained a concentration not significantly different from [Fura-2/AM]e. Under such conditions, however, Fura-2/AM also accumulated in the arterial wall. Although incompletely de-esterified, Fura-2/AM metabolites produced by in vitro incubation of Fura-2/AM with pig liver esterases could be easily detected, fluorescent forms of Fura-2 with a different sensitivity for calcium were not detected in arterial extracts.

Blood and plasma glutathione measured in healthy subjects by HPLC: relation to sex, aging, biological variables, and life habits

We report an HPLC method for measuring the concentrations of reduced (GSH) and total (GSHt) free glutathione in human plasma and whole blood. The chromatographic step was coupled with a postcolumn derivatization reaction and fluorometric detection. The linear range was 0.81-13.02 mumol/L, and the detection limit was 0.13 mumol/L. In healthy adults (ages 18-73 years), mean concentrations were 941 +/- 155 mumol/L for GSHt and 849 +/- 63 mumol/L for GSH in blood (107 men, 94 women), and 3.39 +/- 1.04 mumol/L for GSH in plasma (66 men, 58 women). Blood GSHt but not GSH was significantly lower in children (32 boys, 32 girls: 872 +/- 157 mumol/L) than in adults. Blood GSHt and GSH appeared to be correlated positively with the number of cigarettes smoked per day and the regular practice of physical exercise, and negatively with alcohol abstinence. We observed positive correlations between blood GSHt and cholesterol and calcium concentrations, and between blood GSH and cholesterol concentration.

Blood and plasma glutathione measured in healthy subjects by HPLC: relation to sex, aging, biological variables, and life habits

We report an HPLC method for measuring the concentrations of reduced (GSH) and total (GSHt) free glutathione in human plasma and whole blood. The chromatographic step was coupled with a postcolumn derivatization reaction and fluorometric detection. The linear range was 0.81-13.02 mumol/L, and the detection limit was 0.13 mumol/L. In healthy adults (ages 18-73 years), mean concentrations were 941 +/- 155 mumol/L for GSHt and 849 +/- 63 mumol/L for GSH in blood (107 men, 94 women), and 3.39 +/- 1.04 mumol/L for GSH in plasma (66 men, 58 women). Blood GSHt but not GSH was significantly lower in children (32 boys, 32 girls: 872 +/- 157 mumol/L) than in adults. Blood GSHt and GSH appeared to be correlated positively with the number of cigarettes smoked per day and the regular practice of physical exercise, and negatively with alcohol abstinence. We observed positive correlations between blood GSHt and cholesterol and calcium concentrations, and between blood GSH and cholesterol concentration.

The nucleotide mapping of DNA double-strand breaks at the CYS3 initiation site of meiotic recombination in Saccharomyces cerevisiae

Initiation of meiotic recombination in the yeast Saccharomyces cerevisiae occurs by localized DNA double-strand breaks (DSBs) at several locations in the genome, corresponding to hot spots for meiotic gene conversion and crossing over. The meiotic DSBs occur in regions of chromatin that are hypersensitive to nucleases. To gain insight into the molecular mechanism involved in the formation of these DSBs, we have determined their positions at the nucleotide level at the CYS3 hot spot of gene conversion on chromosome I. We found four major new features of these DSBs: (i) sites of DSBs are multiple with varying intensities and spacing within the promoter region of the CYS3 gene; (ii) no consensus sequence can be found at these sites, indicating that the activity involved in DSB formation has little or no sequence specificity; (iii) the breaks are generated by blunt cleavages; and (iv) the 5' ends are modified in rad50S mutant strains, where the processing of these ends is known to be prevented. We present a model for the initiation of meiotic recombination taking into account the implications of these results.

Electrochemical oxidation of CBS-113 A, a new anti-inflammatory drug: applicability to liquid chromatography-electrochemical detection

The electrochemical properties of a new non-steroidal anti-inflammatory drug (2-hydroxy-4-methylphenyl-2-aminothiazole hydrochloride; CBS-113 A) have been studied using voltammetry in direct current and cyclic modes at glassy carbon disk electrodes. The results show an oxidative process with a diffusion-controlled and a reversible mechanism; these data agree with those obtained in a reversed-phase high-performance liquid chromatography (HPLC) system coupled either with amperometric (single glassy carbon electrode) or coulometric detection (two porous graphite electrodes in series) set at potentials of +0.65 V (vs. Ag/AgCl) and +0.4 V (vs. Pd/H2), respectively. Similar electrochemical properties were found for 2-hydroxyphenyl-2-amino-5'-methylthiazole hydrochloride (RD-1546) which is a potential internal standard. An HPLC system coupled with a UV detector (lambda = 272 nm) and an amperometric detector (+0.65 V) showed a gain in sensitivity of about 10 using electrochemical detection (ED) for the determination of CBS-113 A in human plasma. Linearity range, precision and accuracy were calculated and showed the potential application of HPLC-ED to pharmacokinetic studies of CBS-113 A in plasma.

Influence of sample preparation on cellular glutathione recovery from adherent cells in culture

During the last decade, the unbound glutathione content of cultured adherent cells has become a very important biological marker for many pharmacological and toxicological in vitro studies with regard to the protective role of the tripeptide in its reduced form (GSH). However, the literature does not provide extensive information on the influence of sample preparation on cellular GSH and thiol analyses. Using the fibroblast-like V79 cell line as model, we undertook a comparative study of the efficiency of different procedures reported in the literature with respect to GSH recovery. Depending on the preanalytical step, up to 10-fold discrepancies could be observed in the recovery of intracellular GSH. Different parameters that must be controlled in order to maximize GSH recovery are discussed. The optimal strategy consisted in rapid perchloric acid deproteinization performed directly in the dish, which was extremely valuable for preparing GSH samples from adherent cells, and especially from cells expressing elevated gamma-glutamyl transferase activity.

Ion-exchange liquid chromatography method with indirect UV detection for the assay of choline in pharmaceutical preparations

A high-performance liquid chromatography (HPLC) method coupled with indirect UV spectrophotometric detection was developed for the routine control of pharmaceutical preparations containing choline. Optimization of the HPLC system using silica-based cation exchange columns was focused on the combination in the mobile phase between a UV transparent co-ion and a UV active cationic probe. The selected mobile phase consisted of a mixture of ethanol-ammonium acetate buffer (100 mM, pH 5.0) (20:80, v/v) containing 0.3 mM of 3-hydroxytyramine as chromophoric probe; UV detection was operated at 280 nm. The HPLC system provided full selectivity with regard to the multi-ingredient pharmaceutical matrices tested. Quantitative analysis was validated by testing linearity of the method between 50 and 150% of the theoretical content (coefficient of correlation greater than 0.99) and repeatability (relative standard deviation less than 2.5%; n = 5).

Initiation of recombination in Saccharomyces cerevisiae haploid meiosis

In most eukaryotes during prophase I of meiosis, homologous chromosomes pair and recombine by coordinated molecular and cellular processes. To directly test whether or not the early steps of the initiation of recombination depend on the presence of a homologous chromosome, we have examined the formation and processing of DNA double-strand breaks (DSBs, the earliest physical landmark of recombination initiation) in various haploid Saccharomyces cerevisiae strains capable of entering meiosis. We find that DSBs occur in haploid meiosis, showing that the presence of a homolog is not required for DSB formation. DSBs occur at the same positions in haploid and diploid meioses. However, these two types of meiosis exhibit subtle differences with respect to the timing of formation and levels of DSBs. In haploid meiosis, a slower rate of DSB formation and a reduction in the frequency of DSB (at one of the three sites analyzed) were observed. These results might indicate that interactions between homologs play a role in the formation of meiotic DSBs. Furthermore, haploid strains exhibit a pronounced delay in the disappearance of meiotic DSBs compared to diploid strains, which suggests that sister chromatid interactions for DSB repair are inhibited in haploid meiosis.

Determination of josamycin residues in porcine tissues using high-performance liquid chromatography with pre-column derivatization and spectrofluorimetric detection

A simple, selective and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the measurement of josamycin residues in four porcine tissues (i.e., muscle, liver, kidney and fat). The sample preparation consisted of a homogenization step in an acetonitrile-10 mmol l-1 phosphate buffer mixture, pH 6.0 (35 + 65), centrifugation and a liquid-liquid extractive clean-up of the resulting supernatant with isooctane. Pre-column derivatization of josamycin was performed using cyclohexa-1,3-dione in ammonium acetate buffer, pH 5.0 (90 degrees C for 2 h). The derivative was chromatographed in an isocratic reversed-phase HPLC system. A LiChrospher RP 18 end-capped (5 microns) column was eluted with an acetonitrile-methanol-10 mmol l-1 phosphate buffer mixture, pH 6.0 (45 + 5 + 50). The capacity factor of the josamycin derivative was 17.5. Detection was achieved using spectrofluorimetry (lambda ex = 375 nm; lambda em = 450 nm). The structure of the derivative was assessed by using mass spectrometry. Full selectivity was obtained in the HPLC system versus other macrolide antibiotics (tylosin, spiramycin and erythromycin), aldehydes (formaldehyde, acetaldehyde and benzaldehyde) and endogenous compounds. Linearity and repeatability were tested. Correlation coefficients, for calibration curves in the range of 0.1-3.2 micrograms g-1, were greater than 0.999 for all tissues and the relative standard deviation (S(r)) was 4.9% (1.6 micrograms g-1; n = 6); recovery was higher than 88%.

Changes in chromatin structure at recombination initiation sites during yeast meiosis

Transient double-strand breaks (DSBs) occur during Saccharomyces cerevisiae meiosis at recombination hot spots and are thought to initiate most, if not all, homologous recombination between chromosomes. To uncover the regulatory mechanisms active in DSB formation, we have monitored the change in local chromatin structure at the ARG4 and CYS3 recombination hot spots over the course of meiosis. Micrococcal nuclease (MNase) digestion of isolated meiotic chromatin followed by indirect end-labeling revealed that the DSB sites in both loci are hypersensitive to MNase and that their sensitivity increases 2- to 4-fold prior to the appearance of meiotic DSBs and recombination products. Other sensitive sites are not significantly altered. The study of hyper- and hypo-recombinogenic constructs at the ARG4 locus, also revealed that the MNase sensitivity at the DSB site correlates with both the extent of DSBs and the rate of gene conversion. These results suggest that the local chromatin structure and its modification in early meiosis play an important role in the positioning and frequency of meiotic DSBs, leading to meiotic recombination.

Human core temperature minimum can be modified by ambient thermal transients

By using slow linear thermal transients (+/- 0.025 degree C/min) of reduced amplitude (+/- 3 degrees C around thermoneutrality), we were able to advance the minimum of human internal temperature (Ti) during nocturnal sleep. During experimental night the minimum of esophageal (Tes) and rectal (Tre) temperature were respectively advanced by 1.6 h (P < 0.01) and 2.6 h (P < 0.001) in comparison to reference night spent at thermoneutrality. It must be emphasized that the provoked advance of nocturnal Ti minimum was not accompanied by any change in sleep latency, efficiency, SWS and REM sleep percentages. The result shows that appropriate ambient temperature transient changes could be used to modify the course of human Ti one of the major biological rhythms usually considered as resistant to sleep-wake rhythm manipulation.

High-performance liquid chromatographic enantioselective assay for the measurement of ketoprofen glucuronidation by liver microsomes

A stereoselective high-performance liquid chromatographic (HPLC) method was developed to study the in vitro glucuronidation of ketoprofen enantiomers by liver microsomes. The HPLC system consisted of a Superspher 100 RP 18 end-capped column eluted with a mixture of acetonitrile and 10 mM tetrabutylammonium bromide in 1 mM potassium phosphate adjusted to pH 4.3 (30:70, v/v). Ultraviolet detection was performed at a wavelength of 254 nm. The capacity factors of S-ketoprofen glucuronide, R-ketoprofen glucuronide and R,S-ketoprofen were 12.8, 14.5 and 18.1, respectively. Sample pretreatment consisted of protein precipitation in microsomal incubation suspensions and further purification on a Sep Pak C18 cartridge before injection onto the HPLC system. Quantitation was performed with standard glucuronides biosynthetized with immobilized microsomes and purified by semi-preparative HPLC. The linearity of the method between 1.25 and 25.0 micrograms ml-1 (coefficient of correlation greater than 0.999), the repeatability (coefficient of variation = 1.2%; n = 5), and recovery (within 85%) were tested. The limit of detection was 10 ng for each glucuronide injected. The in vitro glucuronidation of R- and S-ketoprofen was measured in liver microsomes from man and from various animal species (dog, rat, rabbit). For both enantiomers, dog presented the highest specific activity. In contrast, the lowest activity was found in rabbit. On the other hand, the formation ratio of the S- and R-glucuronides of ketoprofen was close to 1 in man, rat and rabbit, but was 4.5 in dog, thus indicating that the reaction was stereoselective in this species.

Polarity of meiotic gene conversion in fungi: contrasting views

The frequency of meiotic gene conversion often varies linearly from one end of the gene to the other. This phenomenon has been called 'polarity'. In this review, we will primarily studies of polarity that have been done in the yeast Saccharomyces cerevisiae (ARG4 and HIS4 loci) and in Ascobolus (b2 locus) with an emphasis on possible mechanisms. The genetic and physical data obtained at these 'hotspots' of recombination strongly suggests that the formation of a polarity gradient reflects both the frequency of heteroduplex formation and the processing of this recombination intermediate by mismatch-repair-dependent processes.

Homologous, homeologous, and illegitimate repair of double-strand breaks during transformation of a wild-type strain and a rad52 mutant strain of Saccharomyces cerevisiae

Different modes of in vivo repair of double-strand breaks (DSBs) have been described for various organisms: the recombinational DSB repair (DSBR) mode, the single-strand annealing (SSA) mode, and end-to-end joining. To investigate these modes of DSB repair in Saccharomyces cerevisiae, we have examined the fate of in vitro linearized replicative plasmids during transformation with respect to several parameters. We found that (i) the efficiencies of both intramolecular and intermolecular linear plasmid DSB repair are homology dependent (according to the amount of DNA used during transformation [100 ng or less], recombination between similar but not identical [homeologous] P450s sequences sharing 73% identity is 2- to 18-fold lower than recombination between identical sequences); (ii) the RAD52 gene product is not essential for intramolecular recombination between homologous and homeologous direct repeats (as in the wild-type strain, recombination occurs with respect to the overall alignment of the parental sequences); (iii) in contrast, the RAD52 gene product is required for intermolecular interactions (the rare transformants which are obtained contain plasmids resulting from deletion-forming intramolecular events involving little or no sequence homology); (iv) similarly, sequencing data revealed examples of intramolecular joining within the few terminal nucleotides of the transforming DNA upon transformation with a linear plasmid with no repeat in the wild-type strain. The recombinant junctions of the rare illegitimate events obtained with S. cerevisiae are very similar to those observed in the repair of DSB in mammalian cells. Together, these and previous results suggest the existence of alternative modes for DSB repair during transformation which differ in their efficiencies and in the structure of their products. We discuss the implications of these results with respect to the existence of alternative pathways and the role of the RAD52 gene product.

Local sweating responses during recovery sleep after sleep deprivation in humans

Changes in the central control of sweating were investigated in five sleep-deprived subjects (kept awake for 40 h) during their recovery sleep under warm ambient conditions [operative temperature (T(o)) was either 35 or 38 degrees C]. Oesophageal (T(oes)) and mean skin (Tsk) temperatures, chest sweat rate (msw,ch), and concomitant electro-encephalographic data were recorded. Throughout the night at 35 or 38 degrees C T(o), msw,ch changes were measured at a constant local chest skin temperature (Tch) of 35.5 degrees C. The results showed that body temperatures (T(oes) and Tsk) of sleep-deprived subjects were influenced by thermal and hypnogogic conditions. The msw,ch levels correlated positively with T(oes) in the subjects studied during sleep stage 1-2 (light sleep: LS), sleep stage 3-4 (slow wave sleep: SWS) and rapid eye movement (REM) sleep. Contrary to what has been reported in normal sleep, firstly, the T(oes) threshold for sweating onset differed between REM sleep and both LS and SWS, and, secondly, the slopes of the msw,ch versus T(oes) relationships were unchanged between REM and non-REM (i.e. LS or SWS) sleep. The changes observed after sleep deprivation were hypothesized to be due to alterations in the functioning of the central nervous system controller.

Cutinase, a lipolytic enzyme with a preformed oxyanion hole

Cutinases, a group of cutin degrading enzymes with molecular masses of around 22-25 kDa (Kolattukudy, 1984), are also able to efficiently hydrolyse triglycerides (De Geus et al., 1989; Lauwereys et al., 1991), but without exhibiting the interfacial activation phenomenom (Sarda et al., 1958). They belong to a class of proteins with a common structural framework, called the alpha/beta hydrolase fold (Martinez et al., 1992; Ollis et al., 1992). We describe herein the structure of cutinase covalently inhibited by diethyl-p-nitrophenyl phosphate (E600) and refined at 1.9-A resolution. Contrary to what has previously been reported with lipases (Brzozowski et al., 1991; Derewenda et al., 1992; Van Tilbeurgh et al., 1993), no significant structural rearrangement was observed here in cutinase upon the inhibitor binding. Moreover, the structure of the active site machinery, consisting of a catalytic triad (S120, H188, D175) and an oxyanion hole (Q121 and S42), was found to be identical to that of the native enzyme, whereas the oxyanion hole of Rhizomucor lipase (Brzozowski et al., 1991; Derewenda et al., 1992), like that of pancreatic lipase (van Tilbeurgh et al., 1993), is formed only upon enzyme-ligand complex formation. The fact that cutinase does not display interfacial activation cannot therefore only be due to the absence of a lid but might also be attributable to the presence of a preformed oxyanion hole.

Interaction of the alerting effect of noise with partial sleep deprivation and circadian rhythmicity of vigilance

Only a few studies have been devoted to the interaction of noise with sleep deprivation and time of day. In a previous study we demonstrated that noise had an alerting effect on cognitive performance during the early night but not during the late night. However, it was not clear whether these different effects of noise were related to prior sleep debt or to time of day as both factors varied simultaneously. In the present experiment, we further studied this issue to identify which of these two factors was responsible for the noise effects. Analysis showed that, when performance was tested at different times with an equivalent prior sleep debt, noise improved speed of response at 0500 but not at 0800 at which variability of response time increased. Noise had no effect on errors. It is suggested that the effect of noise depends on the underlying arousal and raises arousal from its low level due either to time of day or to partial sleep deprivation.

Prevalence of headache in a representative sample of the population in a French department (Haute-Vienne-Limousin)

In 1986-1987, a neuroepidemiologic survey was undertaken to study the prevalence of the most frequently encountered neurologic disorders, and in particular headache, in a representative sample of the population in the Haute-Vienne Department (Limousin). A door-to-door survey was made using a protocol developed by the W.H.O. at the beginning of the 1980's. The calculated prevalences (according to Poisson's distribution) per 100,000 inhabitants were 5,059 for nonmigraine headache, and 4,270 for migraine headache. This disorder preferentially affected young adults and essentially involved females. It was the most frequently encountered disorder (50%) during the different surveys of similar methodology.

Identification of two divergently transcribed genes centromere-proximal to the ARG4 locus on chromosome VIII of Saccharomyces cerevisiae

We have sequenced a 3296 bp segment of the chromosome VIII adjacent to the 3' end of the ARG4 gene. This segment contains two divergently oriented open reading frames (YSC83 and YSC84). Northern blot analysis showed the presence of transcripts corresponding to these two open reading frames in vegetative cells. Levels of these transcripts increase five to ten-fold during sporulation. These two genes are not essential for vegetative growth or sporulation. Analysis of the putative protein products on the SwissProt database revealed that the C-terminal region of the Ysc84 protein contains a putative SH3 domain.

A structural analysis of the bent kinetoplast DNA from Crithidia fasciculata by high resolution chemical probing

The chemical probes potassium permanganate (KMnO4) and diethylpyrocarbonate (DEPC) have been used to study the conformation of bent kinetoplast DNA from Crithidia fasciculata at different temperatures. Chemical reactivity data shows that the numerous short A-tracts of this bent DNA adopt a similar structure at 43 degrees C. This conformation appears to be very similar to the conformation of A-tracts in DNA exhibiting normal gel mobility. The A-tract structure detected by chemical probing is characterized by a high degree of base stacking on the thymine strand, and by an abrupt conformational change at the 3' end of the adenine strand. In general, no major alteration of this A-tract specific structure was detected between 4-53 degrees C. However, probing with KMnO4 revealed two unusual features of the C. fasciculata sequence that may contribute to the highly aberrant gel mobility of this DNA: 1) the B DNA/A-tract junction 5' dC/A3-6 3'. 5' dT3-6/G 3' is disproportionately represented and is conformationally distinct from other 5' end junctions, and 2) low temperature favors a novel strand-specific conformational distortion over a 20 base pair region of the bent kinetoplast DNA. Presence of the minor groove binding drug distamycin had little detectable effect on the A-tract conformation. However, distamycin did inhibit formation of the novel KMnO4 sensitive low temperature structure and partially eliminated the anomalous gel mobility of the kinetoplast DNA. Finally, we describe a simple and reproducible procedure for the production of an adenine-specific chemical DNA sequence ladder.

The control in cis of the position and the amount of the ARG4 meiotic double-strand break of Saccharomyces cerevisiae

During meiosis, a transient DNA double-strand break (DSB) occurs in the promoter region (positions -200/-185) of the Saccharomyces cerevisiae ARG4 gene and is a likely intermediate in the initiation of meiotic gene conversion events in this region. We report here a functional analysis of the ARG4 DSB based on the study of various deletions in this chromosomal region. We have identified several cis-acting elements located within the -465/+3 region of the ARG4 promoter that control the formation of this DSB. The -465/-317 region includes a transcription terminator and is necessary for a normal amount of ARG4 DSB, but not for its positioning. The -316/-140 region can be replaced by an unrelated DNA sequence where a meiotic DSB then occurs, suggesting that the site of DSB is not sequence-specific, but is positioned at a fixed distance from the adjacent -139/+3 region. Also, in all strains constructed, the amount of meiotic DSB is correlated with the frequency of gene conversion in ARG4, which provides a strong argument for the initiation of gene conversion by a DSB in this region of the yeast genome.

Rapid liquid chromatographic assay of glutathione in cultured cells

A rapid, sensitive and selective method for the assay of glutathione in cultured cells has been developed using ion-pair reversed phase rapid high performance liquid chromatography. The use of a 4 micron particle, 5 cm long column (Superspher 100 RP 18 end-capped) allowed complete analysis of glutathione within 3 min. A postcolumn derivatization reaction with o-phthalaldehyde and fluorometric detection made the assay fully selective with regard to other endogenous thiols and sensitive (the detection limit was 0.5 ng of glutathione injected). The linearity range was between 0.1 and 2.0 microgram/mL with good repeatability (relative standard deviation less than 5% for the lowest concentration quantitated). Recoveries of GSH from cultured cell samples were above 98%. The rapid analysis enabled the processing of a large number of samples in a short time (up to 20 per hour). The method was applied to the measurement of the intracellular glutathione amount in V79 fibroblasts along cell growth in culture.

[T.O.M. ointment, breast feeding and serum estradiol in newborn infants. A double-blind, randomized controlled study]

OBJECTIVE

To study whether there is an iatrogenic transfer of oestradiol through the use of T.O.M. ointment administered to prevent or to cure trophic changes in the breast while breastfeeding and what the dangers of plasma levels of oestradiol in the newborn will be.

TYPE OF STUDY

Controlled, randomised, double blind.

SUBJECTS AND METHODS

80 mother/infant couples were included in the study: 40 received the ointment containing oestradiol (the treated group), and 40 received an ointment without oestradiol (the non-treated group); the ointment was applied before each breastfeeding from the 2nd to the 6th or 7th day of life. Mothers' milk and blood from the newborn babies were taken for estimating the levels of oestradiol using a radio-immunological technique. The total quantity of ointment was measured for each subject.

RESULTS

The mean level of oestradiol in the treated mothers' milk was significantly higher (p. 0.0014) than in the milk of the mothers who had not been treated. The concentration of oestradiol in the plasma of the newborn dropped from the first to the last day of the trial without any difference in the treated or non-treated groups no matter what the sex of the child was, nor the quantity of ointment used.

Electroencephalogram and cardiovascular responses to noise during daytime sleep in shiftworkers

Intermittent noise occurring during sleep has been found to induce heart rate, peripheral vasomotor and electroencephalogram (EEG) changes. This study analysed these responses during the daytime and night-time sleep of shiftworkers doing a three shift system, to determine the influence of the inversion of the sleep-wake cycle on the sensitivity to noise. A group of 14 shiftworkers [aged 37 (SD 5) years] underwent an habituation daytime sleep, two experimental daytime sleeps and a night-time sleep. Traffic noises were presented during sleep [truck, 71 dB(A); motorbike, 67 dB(A); and car, 64 dB(A)] at a rate of nine each hour. The EEG measurements of sleep, electrocardiogram and finger pulse amplitude were recorded continuously. The results were expressed by computing the percentage of observed cardiac response (%HRR) and vasoconstrictive response (%FPR), magnitude of heart rate variation (heart rate response; HRR), percentage of reduction of the digital blood flow (finger pulse response, FPR), cardiac cost (CC = % HRR x HRR) and vasomotor cost (VC = % FPR x FPR). The results showed that, compared to night-time sleep, there was change in the structure of daytime sleep, that is an increase in slow wave sleep (SWS), especially stage 4 sleep decrease of stage 2 and rapid eye movement (REM) sleep latencies, and an earlier SWS and REM sleep barycentric point. During daytime sleep the % FPR was significantly smaller in SWS than in stage 2 or REM sleep. Large differences were observed in % HRR, HRR and CC between daytime sleep stages (SWS less than stage 2 less than REM sleep).(ABSTRACT TRUNCATED AT 250 WORDS)

The Saccharomyces cerevisiae ARG4 initiator of meiotic gene conversion and its associated double-strand DNA breaks can be inhibited by transcriptional interference

In the yeast Saccharomyces cerevisiae, as in other eukaryotes, some regions of the genome have a much higher level of meiotic gene conversion than others. Previous deletion analysis indicated that the sequence necessary for the high level of gene conversion within the ARG4 region defined an initiation site located between positions -316 and -37 [relative to the first base pair (+1) of the ARG4 coding sequence] of the ARG4 promoter. To test whether this sequence is sufficient to promote gene conversion in a novel chromosomal context, we inverted on the chromosome various DNA fragments including the implicated region and the ARG4 coding sequence. Surprisingly, these inversions resulted in the loss of the normal recombination properties and double-strand-break formation associated with this process. By Northern analysis, we found that a transcript traverses the ARG4 initiation site in these inversion mutants but not in the wild type. When transcription through this region was prevented by a transcription terminator, the activity of the initiation site and the formation of double-strand breaks were restored. From these results and from complementary deletion analysis in the normal ARG4 orientation, we conclude that the activity of the ARG4 initiation site requires protection from transcriptional interference.

A multisite integrative cassette for the yeast Saccharomyces cerevisiae

We have developed a cassette for the integration of cloned DNA sequences at multiple sites in the Saccharomyces cerevisiae genome, taking advantage of the naturally repeated sigma sequences. This cassette contains one engineered sigma element which allows the targeting of an embedded gene at different genomic sigma elements by gene replacement. Two yeast genes, ARG4 and URA3, were thus integrated in the absence of any bacterial sequences, individually or sequentially on twelve chromosomes. Consequently, these studies led to the genetical tagging of individual members of the sigma family.

[Blood lactate in the steeplechase horse: triangular and rectangular series of steps during short duration races]

Five steeplechase race horses were observed during incremental and constant-load exercises with the aim of separating effects of work rate and time on blood lactate. Each independent exercise (an incremental and three constant load tests) was a sequence of three two-minute runs, separated by two one-minute rest intervals for jugular blood sampling. The following observations were made: 1. During constant load exercises, in the five horses, blood lactate stabilized below 4 mmol.l-1: lactatemia critical velocity (LVC) = 3.33 +/- 0.16 mmol.l-1. Nevertheless, VCL, critical lactate velocity inducing LVC, was not statistically different from VS4, velocity inducing a 4 mmol.l-1 blood lactate during incremental tests. Remaining reticent on the meaning of "lactate threshold" often attributed to VS4, an incremental exercise thus seemed pertinent for routine long-term surveys of endurance. 2. If delta L is the blood lactate increase within a single short run, delta L increases linearly with running velocity for an incremental test, allowing the calculation of a "null" velocity, the highest velocity for which there is no significant lactate increase. For independent runs, delta L increased exponentially with velocity, with noticeable differences between horses. This individual short-term functional adaptation variability could be considered in assessment and follow-up of race horse fitness.

Recombination between similar but not identical DNA sequences during yeast transformation occurs within short stretches of identity

Interactions between similar but not identical (homeologous) DNA sequences play an important biological role in the evolution of genes and genomes. To gain insight into the underlying molecular mechanism(s) of genetic recombination, we have studied inter- and intramolecular homeologous recombination in S. cerevisiae during transformation. We found that homeologous DNAs recombine efficiently. Hybrid sequences were obtained between two mammalian cytochrome P450 cDNAs, sharing 73% identity, and between the yeast ARG4 gene and its human homeologous cDNA, sharing 52% identity. Sequencing data showed that the preferred recombination events are those corresponding to the overall alignment of the DNA sequences and that the junctions are within stretches of identity of variable length (2-21 nt). We suggest that these events occur by a conventional homologous recombination mechanism.

Effects of noise on sleep inertia as a function of circadian placement of a one-hour nap

The purpose of the present study was to analyse the arousing effects of noise on sleep inertia as a function of circadian placement of a one-hour nap. In a first experiment, we measured the effects of sleep inertia in a neutral acoustic environment after a one-hour nap placed either at 0100 or 0400 on response time during a spatial memory test. In a second experiment were analysed the effects of an intense continuous noise on sleep inertia. The results showed that noise produced a total abolition of sleep inertia after an early nap (0000 to 0100). This may be due to the arousing effect of noise; however, results are less clear after a late nap 0300 to 0400 as noise seems to be ineffective. This result is discussed in terms of either a function of time-of-day effect or of prior sleep intensity. Moreover, our data suggest a possible interaction of noise with partial sleep deprivation leading to a slight deleterious effect those subjects who did not sleep at all.

The pharmacokinetics of tiopronin and its principal metabolite (2-mercaptopropionic acid) after oral administration to healthy volunteers

We have studied the pharmacokinetics of tiopronin and its principal metabolite, 2-mercaptopropionic acid (2-MPA) in healthy volunteers after the oral administration of 500 mg (2 Acadione tablets), followed by simultaneous assay of the two compounds in plasma over a period of 48 h using a new method (emission of fluorescence after HPLC and post-column derivatization by pyrene-maleimide). The absorption of tiopronin was slow (tmax between 4 and 6 h) and the plasma concentrations subsequently fell biexponentially. The principal metabolite 2-MPA appeared later in the plasma (tmax between 10 and 12 h after a lag-time of 3 h) then disappeared monoexponentially. About 15% of the tiopronin was metabolized to 2-MPA.

Meiotic recombination on artificial chromosomes in yeast

We have examined the meiotic recombination characteristics of artificial chromosomes in Saccharomyces cerevisiae. Our experiments were carried out using minichromosome derivatives of yeast chromosome III and yeast artificial chromosomes composed primarily of bacteriophage lambda DNA. Tetrad analysis revealed that the artificial chromosomes exhibit very low levels of meiotic recombination. However, when a 12.5-kbp fragment from yeast chromosome VIII was inserted into the right arm of the artificial chromosome, recombination within that arm mimicked the recombination characteristics of the fragment in its natural context including the ability of crossovers to ensure meiotic disjunction. Both crossing over and gene conversion (within the ARG4 gene contained within the fragment) were measured in the experiments. Similarly, a 55-kbp region from chromosome III carried on a minichromosome showed crossover behavior indistinguishable from that seen when it is carried on chromosome III. We discuss the notion that, in yeast, meiotic recombination behavior is determined locally by small chromosomal regions that function free of the influence of the chromosome as a whole.

Urinary glucuronide excretion of fenofibric and clofibric acid glucuronides in man. Is it polymorphic?

The possible polymorphism of the glucuronidation reaction in man has been investigated using two hypolipidaemic compounds, fenofibrate and clofibrate, as the test probes. The formation of fenofibryl and clofibryl glucuronides was identified by their susceptibility to hydrolyses by beta-glucuronidase. The urinary excretion of the glucuronides was measured in 72 healthy volunteers after a single dose of fenofibrate, and in 104 subjects given a single dose of clofibric acid. Fenofibrate was excreted at a lower rate than clofibrate, since 13.94% and 26.55% of the doses of fenofibrate and clofibrate respectively, were recovered in urine in 8 h. Correlation analysis indicated that sex and body mass index significantly influenced the formation of fenofibryl glucuronide, whereas age and oral contraceptives affected the excretion of clofibryl acid glucuronide. The 8-hour urinary excretion patterns of clofibryl glucuronide and of clofibric acid presented a Gaussian distribution, whereas those of fenofibryl glucuronide and fenofibric acid showed 2 populations. When the metabolic ratio free fenofibric acid/glucuronide was considered, 84.7% of subjects presented the ratio 0.147, and 15.3% had the 3-fold higher ratio of 0.421. The study has shown, in the human population studied, that the glucuronidation of fenofibric acid but not that of clofibric acid may present a polymorphism.

Highly sensitive immuno-assays for the determination of cotinine in serum and saliva. Comparison between RIA and an avidin-biotin ELISA

Two immuno-assay methods (RIA and ELISA) have been developed for the accurate and sensitive measurement of cotinine in human body fluids (serum, saliva). RIA uses [3H]cotinine as antigen and charcoal/dextran for separating cotinine-bound antibodies from the free derivative. Another technique (ELISA) was developed to avoid the use of radio-labelled compounds and to determine cotinine in large populations, including passive or non-smokers who usually present very low concentrations. The two techniques were analytically validated. The detection limit was similar (0.1 micrograms/l) and the precision was better than 10% for both techniques. Non-smoker values ranged from 0.1 to 17 micrograms/l by ELISA and 0.1 to 27.5 micrograms/l by RIA, whereas smoker values ranged from 50 to 1000 micrograms/l (ELISA) and from 70 to 800 micrograms/l (RIA). The comparative analysis of cotinine in 96 human sera revealed a good correlation between the two methods (r = 0.97) and a reliable discrimination between the populations of non-smokers and smokers. As usual, the ELISA is more rapid (4 h 30 min) than the RIA (longer than 48 h). ELISA is proposed for use in the epidemiological investigation of the human tobacco risk.

Determination of 2-mercaptopropionylglycine and its metabolite, 2-mercaptopropionic acid, in plasma by ion-pair reversed-phase high-performance liquid chromatography with post-column derivatization

A simple and fast high-performance liquid chromatographic method was developed for the simultaneous measurement of 2-mercaptopropionylglycine (Tiopronine) and its metabolite (2-mercaptopropionic acid) in human plasma after the administration of a pharmaceutical dosage form (Acadione). The sample treatment before high-performance liquid chromatographic analysis consisted of the reduction of the corresponding disulphides by tri-n-butylphosphine and protein precipitation with ethanol. Separation was achieved by ion-pair high-performance liquid chromatography on a reversed-phase column (LiChrospher RP 18e) with cetrimonium bromide as counter ion and detection by fluorimetry after post-column derivatization with a selective thiol reagent, i.e. pyrenemaleimide. The high frequency of the analyzed samples and validation results make the method suitable for pharmacokinetic studies, and this was demonstrated by the first results obtained after the administration of an oral dose of 500 mg of Tiopronine to two healthy subjects.

Oral contraceptives stimulate the excretion of clofibric acid glucuronide in women and female rats

1. Glucuronidation of clofibric acid, the pharmacologically active form of the hypolipidemic drug clofibrate was investigated in a human population, either in vitro with liver homogenates from biopsies, or after ingestion of the drug and determination of the urinary metabolite. No difference in the glucuronidation rate according to age of the patients was observed. Bilirubin but not clofibric acid glucuronidation was significantly higher in women (106% increase), when expressed per gram of tissue. 2. The excretion of clofibryl glucuronide in women who took oral contraceptives was significantly enhanced by 25%. 3. In female rats, treatment with the contraceptive agent norethindrone also stimulated by 48% the formation of clofibrylglucuronide in liver microsomes.

Detection of heteroduplex DNA molecules among the products of Saccharomyces cerevisiae meiosis

We have used denaturant-gel electrophoresis to provide a physical demonstration of heteroduplex DNA in the products of yeast meiosis. We examined heteroduplex formation at arg4-nsp, a G.C----C.G transversion that displays a moderately high level of postmeiotic segregation. Of the two possible arg4-nsp/ARG4 mismatches (G.G and C.C), only C.C was detected in spores from mismatch repair-competent (Pms1+) diploids. In contrast, C.C and G.G were present at nearly equal levels in spores from Pms1- diploids. These results confirm previous suggestions that postmeiotic segregation spores contain heteroduplex DNA at the site of the marker in question, that C.C is repaired less frequently than is G.G, and that the PMS1 gene product plays a role in mismatch correction. Combined with the observation that Pms1+ ARG4/arg4-nsp diploids produce 3 times more 3+:5m (wildtype:mutant) tetrads (+, +, +/m, m) than 5+:3m tetrads (+, +/m, m, m), these results indicate that, during meiosis, formation of heteroduplex DNA at ARG4 involves preferential transfer of the sense (nontranscribed) strand of the DNA duplex.

Protein engineering by cDNA recombination in yeasts: shuffling of mammalian cytochrome P-450 functions

We have constructed, in the yeast Saccharomyces cerevisiae, a mosaic assembly of genes by in vivo recombination of partially homologous sequences. The approach was tested on cDNAs encoding functionally distinct mammalian cytochromes P-450 (P-450). The selection for recombinant cDNAs used the transformation of yeast cells, which required the recircularization of a linearized plasmid by recombination of two partially homologous cDNAs. Libraries of mosaic genes with bipartite or tripartite structures were generated by intramolecular and intermolecular recombination events. The presence of yeast promoter and terminator sequences on the flanking sides of the recombined cDNAs has allowed the synthesis of encoded mosaic proteins. A library of yeast clones producing recombinant mouse P-450 P1 and rabbit P-450 LM4 was screened using functional criteria to identify chimeras with shuffled substrate specificity. Restriction mapping of mosaic genes, biochemical analysis of the synthesized proteins, comparison of chimeric enzymes, and the alignment of sequences with bacterial P-450 camphor hydroxylase of known three-dimensional structure, all suggest that the P-450 P1 amino acid residues 203-238 play a major role in the control of cytochrome activity toward carcinogenic polycyclic aromatic hydrocarbons. Similar approaches to structure-function analysis are believed to be applicable to other protein families.