Peel bond strength between 3D printing tray materials and elastomeric impression/adhesive systems: A laboratory study.

OBJECTIVES: The present study aimed to evaluate the bonding between three 3D printed custom tray materials and three elastomeric impression/adhesive systems using the peel test. METHODS: Test blocks were 3D printed by three different technologies using Dental LT, FREEPRINT tray, and polylactide (PLA) tray materials. The reference test blocks were conventionally fabricated with Zeta Tray LC, a light-curing resin. The surface topographies of the four tray materials were investigated by scanning electron microscopy (SEM) analyses and roughness measurements. The peel bond strength between the four tray materials and three impression/adhesive systems, vinylsiloxanether (VSXE), vinyl polysiloxane (VPS), and polyether (PE), was measured (n=12 per group). The peeling failure modes and rupture sites were identified microscopically. RESULTS: The four tray materials featured different surface topographies. The peel bond strength was not significantly different with VSXE and PE, but PLA and the reference showed higher peel bond strength with VPS than the Dental LT and FREEPRINT tray (p<0.05). The rupture site of adhesive failure in all groups was partly at the adhesive-impression material interface and partly within the adhesive but never at the adhesive-tray material interface. SIGNIFICANCE: The 3D printed tray materials can achieve satisfactory chemical compatibility with the adhesives of VSXE, VPS, and PE. Surface topographies generated by the 3D printing technologies may affect bonding. Generally, 3D printed tray materials can provide clinically adequate bond strength with the elastomeric impression/adhesive systems. PLA is recommended for bonding with VPS when severe impression removal resistance is detected.

Comparative evaluation of topographical data of dental implant surfaces applying optical interferometry and scanning electron microscopy.

OBJECTIVE: Comparability of topographical data of implant surfaces in literature is low and their clinical relevance often equivocal. The aim of this study was to investigate the ability of scanning electron microscopy and optical interferometry to assess statistically similar 3-dimensional roughness parameter results and to evaluate these data based on predefined criteria regarded relevant for a favorable biological response. METHODS: Four different commercial dental screw-type implants (NanoTite Certain Prevail, TiUnite Brånemark Mk III, XiVE S Plus and SLA Standard Plus) were analyzed by stereo scanning electron microscopy and white light interferometry. Surface height, spatial and hybrid roughness parameters (Sa, Sz, Ssk, Sku, Sal, Str, Sdr) were assessed from raw and filtered data (Gaussian 50µm and 5µm cut-off-filters), respectively. Data were statistically compared by one-way ANOVA and Tukey-Kramer post-hoc test. For a clinically relevant interpretation, a categorizing evaluation approach was used based on predefined threshold criteria for each roughness parameter. RESULTS: The two methods exhibited predominantly statistical differences. Dependent on roughness parameters and filter settings, both methods showed variations in rankings of the implant surfaces and differed in their ability to discriminate the different topographies. Overall, the analyses revealed scale-dependent roughness data. Compared to the pure statistical approach, the categorizing evaluation resulted in much more similarities between the two methods. SIGNIFICANCE: This study suggests to reconsider current approaches for the topographical evaluation of implant surfaces and to further seek after proper experimental settings. Furthermore, the specific role of different roughness parameters for the bioresponse has to be studied in detail in order to better define clinically relevant, scale-dependent and parameter-specific thresholds and ranges.

Coating of ß-tricalcium phosphate scaffolds-a comparison between graphene oxide and poly-lactic-co-glycolic acid.

Bone regeneration in critical size defects is a major challenge in oral and maxillofacial surgery, and the gold standard for bone reconstruction still requires the use of autologous tissue. To overcome the need for a second intervention and to minimize morbidity, the development of new biomaterials with osteoinductive features is the focus of current research. As a scaffolding material, ß-tricalcium phosphate (ß-TCP) is suitable for bone regeneration purposes, although it does not carry any functional groups for the covalent immobilization of molecules. The aim of the present study was to establish effective coating variants for ß-TCP constructs to enable the biofunctionalization of anorganic blocks with different osteogenic molecules in future studies. We established working protocols for thin surface coatings consisting of polylactic-co-glycolic acid (PLGA) and graphene oxide (GO) by varying parameters. Surface properties such as the angularity and topography of the developed scaffolds were analyzed. To examine biological functionality, the adhesion and proliferation behavior of jaw periosteal cells (JPCs) were tested on the coated constructs. Our results suggest that PLGA is the superior material for surface coating of ß-TCP matrices, leading to higher JPC proliferation rates and providing a more suitable basis for further biofunctionalization in the field of bone tissue engineering.

Cytocompatibility evaluation of different biodegradable magnesium alloys with human mesenchymal stem cells.

In the last few years, the use of biodegradable magnesium (Mg) alloys has evoked great interest in the orthopedic field due to great advantages over long-term implant materials associated with various side effects like allergy and sensitization and consequent implant removal surgeries. However, degradation of these Mg alloys results in ion release, which may cause severe cytotoxicity and undesirable complications after implantation. In this study, we investigated the cytological effects of various Mg alloys on cells that play an important role in bone repair. Eight different magnesium alloys containing varying amounts of Al, Zn, Nd and Y were either incubated directly or indirectly with the osteosarcoma cell line Saos-2 or with uninduced and osteogenically-induced human mesenchymal stem cells (MSCs) isolated from bone marrow specimens obtained from the femoral shaft of patients undergoing total hip replacement. Cell viability, cell attachment and the release of ions were investigated at different time points in vitro. During direct or indirect incubation different cytotoxic effects of the Mg alloys on Saos-2 cells and osteogenically-induced or uninduced MSCs were observed. Furthermore, the concentration of degradation products released from the Mg alloys differed. Overall, Mg alloys MgNd2, MgY4, MgAl9Zn1 and MgY4Nd2 exhibit good cytocompatibility. In conclusion, this study reveals the necessity of cytocompatibility evaluation of new biodegradable magnesium alloys with cells that will get in direct contact to the implant material. Furthermore, the use of standardized experimental in vitro assays is necessary in order to reliably and effectively characterize new Mg alloys before performing in vivo experiments.

Functional differentiation and selective inactivation of multiple Saccharomyces cerevisiae genes involved in very-long-chain fatty acid synthesis.

While de novo fatty acid synthesis uses acetyl-CoA, fatty acid elongation uses longer-chain acyl-CoAs as primers. Several mutations that interfere with fatty acid elongation in yeast have already been described, suggesting that there may be different elongases for medium- and long-chain acyl-CoA primers. In the present study, an experimental approach is described that allows differential characterization of the various yeast elongases in vitro. Based on their characteristic primer specificities and product patterns, at least three different yeast elongases are defined. Elongase I extends C12-C16 fatty acyl-CoAs to C16-C18 fatty acids. Elongase II elongates palmitoyl-CoA and stearoyl-CoA up to C22 fatty acids, and elongase III synthesizes 20-26-carbon fatty acids from C18-CoA primers. Elongases I, II and III are specifically inactivated in, respectively, elo1, elo2 and elo3 mutants. Elongases II and III share the same 3-ketoacyl reductase, which is encoded by the YBR159w gene. Inactivation of YBR159w inhibits in vitro fatty acid elongation after the first condensation reaction. Although in vitro elongase activity is absent, the mutant nevertheless contains 10-30% of normal VLCFA levels. On the basis of this finding, an additional elongating activity is inferred to be present in vivo. ybr159Delta cells show synthetic lethality in the presence of cerulenin, which inactivates fatty acid synthase. An involvement of FAS in VLCFA synthesis may account for these findings, but remains to be demonstrated directly. Alternatively, a vital role for C18 and C20 hydroxyacids, which are dramatically overproduced in ybr159Delta cells, may be postulated.

Abnormal salivary cortisol levels in social phobic patients in response to acute psychological but not physical stress.

BACKGROUND: Little is known about the hypothalamic-pituitary-adrenal axis response to acute stressful behavioral challenges in patients with social phobia. METHODS: Eighteen patients with social phobia and 17 normal volunteers participated in two behavioral stressors: a speech task and physical exercise. RESULTS: Normal volunteers (n = 14) demonstrated a significant 50% increase in salivary cortisol levels to the speech task. Three nonresponding normal volunteers demonstrated a 17% decrease. In contrast, patients with social phobia demonstrated dichotomous changes. Seven social phobia patients demonstrated a significantly higher 90% increase in salivary cortisol to the speech task, whereas the remaining patients (n = 11) were nonresponders demonstrating a 32% decrease in cortisol. Both patient groups were significantly more anxious than the normal volunteers. In contrast to the response to a speech task, social phobics showed a cortisol response to physical exercise of similar magnitude as normal volunteers. CONCLUSIONS: The results indicated dichotomies in magnitude and in distribution of the cortisol response to a speech task between social phobia patients and normal volunteers. Social phobia patients responded differently than normal volunteers to a stressor associated with social evaluation but not to physical exercise. These results suggest adaptation of distinct biological processes specific to different stressful conditions in social phobia.

The antidepressant effect of sertraline is not enhanced by dose titration: results from an outpatient clinical trial.

A previous report suggested that 5 weeks of continued treatment with 20 mg of fluoxetine was approximately as effective as double-blind titration to a dose of 60 mg in patients who had failed to respond to 3 weeks of initial treatment at 20 mg. The current study was undertaken to evaluate whether 150 mg of sertraline was any more effective than 50 mg in treating depressed patients who were non-responders at 3 weeks. Ninety-one outpatients with DSM-IV major depressive disorder who had a 17-item Hamilton Depression Rating Scale (HAM-D) score > or = 18 were treated with open label sertraline for 3 weeks. Patients who did not achieve remission (defined as 17-item HAM-D total score < or = 8 by week 3) were then randomized to 5 more weeks of double-blind treatment with either 50 mg of sertraline or immediate titration to 150 mg of sertraline. Efficacy was assessed at each visit with the HAM-D, Clinical Global Impressions (CGI)-severity and improvement scale, and the Hopkins Symptom Checklist. There were no significant between-group differences in clinical or demographic features at baseline for the three treatment groups. After 3 weeks of open-label treatment, 16 patients were not randomized, of whom 11 (69%) met responder criteria. The remaining patients were randomized, double-blind, to 50 mg of sertraline (n = 37; HAM-D = 19.2 +/- 5.0) or 150 mg of sertraline (n = 38; HAM-D = 18.4 +/- 5.0). PROC-Mixed analyses found no significant difference in slopes for any outcome measure when comparing 50 mg and 150 mg sertraline treatment groups. At week 8 (LOCF), the overall remission rate (HAM-D < or = 8) for 3-week non-responders was 40%, with no statistically significant between-group difference for the 50 mg versus 150 mg doses of sertraline (P > 0.10). A completer analysis yielded similar results. Adverse events were mostly mild on both doses of sertraline and led to few treatment discontinuations. The results suggest that for most patients continued treatment with 50 mg dose of sertraline yields a rate of antidepressant response that is comparable to what is achieved by dose escalation from 50 mg to 150 mg of sertraline after 3 weeks of treatment. While some patients clearly benefit from higher doses, the results of the current study are consistent with the lack of any evidence for a dose-response curve with sertraline in the treatment of depression.

A novel function of yeast fatty acid synthase. Subunit alpha is capable of self-pantetheinylation.

The prosthetic group of yeast fatty acid synthase (FAS), 4'-phosphopantetheine, is covalently linked to Ser180 of subunit alpha. It originates from coenzyme A and is transferred to the enzyme by a specific phosphopantetheine:protein transferase (PPTase). The present study demonstrates that the FAS-activating PPTase of yeast represents a distinct catalytic domain of the FAS complex and resides within the C-terminal portion of subunit alpha. The autoactivation capacity of yeast FAS became evident from in vitro pantetheinylation studies using purified apo-FAS preparations. These were readily converted to pantetheinylated holo-FAS simply upon addition of free coenzyme A. Pantetheinylation-competent apo-FAS was prepared in vitro by constructing hybrid oligomers containing alpha-subunits from two different pantetheine-less FAS-mutants. The respective mutants were selected according to their ability to complement each other, in vivo. In vitro formation of hybrid apo-FAS complexes was achieved by dimethylmaleic anhydride (DMMA) -induced reversible dissociation of mixtures of the two constituent mutant enzymes. This treatment was both necessary and sufficient to produce pantetheinylation-competent apo-FAS. Specific FAS activities were comparable independent of whether the apo-enzymes were pantetheinylated in vivo or in vitro. Apart from the induction of overall FAS activity, incorporation of phosphopantetheine into apo-FAS was also demonstrated by the use of 3H-labelled coenzyme A, leading to the formation of radioactively labelled FAS. It is concluded that pantetheinylation of yeast FAS is performed by an intrinsic catalytic activity of the apo-enzyme proper. The endogenous PPTase acts in trans between different subunits alpha in the alpha6beta6 oligomer. The self-pantetheinylation of yeast FAS represents the first example of an apo-enzyme being capable of post-translational autoactivitation.

Identification of the plasma membrane H+-biotin symporter of Saccharomyces cerevisiae by rescue of a fatty acid-auxotrophic mutant.

Bakers' yeast is auxotrophic for biotin (vitamin H) and depends on the efficient uptake of this compound from the environment. A mutant strain with strongly reduced biotin uptake and with reduced levels of protein biotinylation was identified. The strain was auxotrophic for long-chain fatty acids, and this auxotrophy could be suppressed with high levels of biotin in the medium. After transformation of this mutant with a yeast genomic library, the unassigned open reading frame YGR065C was identified to complement this mutation. This gene codes for a protein with 593 amino acids and 12 putative transmembrane helices. Northern blot analysis revealed that, in wild-type cells, the corresponding mRNA levels were increased at low biotin concentrations. Likewise, cellular biotin uptake was increased with decreasing biotin availability. Expression of YGR065C under the control of the constitutive ADH1 promoter resulted in very high biotin transport rates across the plasma membrane that were no longer regulated by the biotin concentration in the growth medium. We conclude that YGR065C encodes the first biotin transporter identified for a non-mammalian organism and designate this gene VHT1 for vitamin H transporter 1.

Highly sensitive gas chromatographic-tandem mass spectrometric method for the determination of morphine and codeine in serum and urine in the femtomolar range.

A sensitive and specific method was developed for the determination of codeine and morphine in human serum and for the determination of trace amounts of endogenous morphine in human urine. The analytes were recovered from serum by a simple liquid-liquid extraction method. Urine samples were hydrolyzed, and purified by two liquid-liquid extraction steps and a solid-phase extraction. Samples were derivatized to the pentafluoropropionic esters and measured by gas chromatography tandem mass spectrometry. Using the deuterated analogues as internal standards a limit of quantification of 20 fmol/ml (5.7 pg/ml) morphine and 500 fmol/ml (150 pg/ml) codeine in human serum and of 2.5 fmol/ml (0.71 pg/ml) morphine in urine was achieved. The method was suitable for the determination of morphine and codeine in pharmacokinetic studies and for the determination of the urinary excretion of endogenous morphine.

Systematic analysis of yeast strains with possible defects in lipid metabolism.

Lipids are essential components of all living cells because they are obligate components of biological membranes, and serve as energy reserves and second messengers. Many but not all genes encoding enzymes involved in fatty acid, phospholipid, sterol or sphingolipid biosynthesis of the yeast Saccharomyces cerevisiae have been cloned and gene products have been functionally characterized. Less information is available about genes and gene products governing the transport of lipids between organelles and within membranes or the turnover and degradation of complex lipids. To obtain more insight into lipid metabolism, regulation of lipid biosynthesis and the role of lipids in organellar membranes, a group of five European laboratories established methods suitable to screen for novel genes of the yeast Saccharomyces cerevisiae involved in these processes. These investigations were performed within EUROFAN (European Function Analysis Network), a European initiative to identify the functions of unassigned open reading frames that had been detected during the Yeast Genome Sequencing Project. First, the methods required for the complete lipid analysis of yeast cells based on chromatographic techniques were established and standardized. The reliability of these methods was demonstrated using tester strains with established defects in lipid metabolism. During these investigations it was demonstrated that different wild-type strains, among them FY1679, CEN.PK2-1C and W303, exhibit marked differences in lipid content and lipid composition. Second, several candidate genes which were assumed to encode proteins involved in lipid metabolism were selected, based on their homology to genes of known function. Finally, lipid composition of mutant strains deleted of the respective open reading frames was determined. For some genes we found evidence suggesting a possible role in lipid metabolism.

Psychomotor performance of long-term benzodiazepine users before, during, and after benzodiazepine discontinuation.

Long-term (mean, 8 years) users of benzodiazepines (BZs) were administered a small battery of cognitive tests on three occasions (before BZ taper, and 5 and 12 weeks post taper) as part of their BZ discontinuation program. Ninety-six patients had 5-week and 77 patients had 12-week data. For taper successes, BZ-free status was confirmed by weekly BZ plasma level determinations. Age and education, as well as baseline test scores, were used as covariates for all data analyses. Patients who successfully tapered off BZ were able to complete symbol copying (SC) and digit symbol substitution (DSST) tasks faster than patients still taking BZ (p < 0.05). In addition, using an adjective check list, patients with taper success, i.e., BZ-free patients, reported lower levels of mental and physical sedation and higher levels of tranquilization (p < 0.05) than did patients still taking BZ. These results were confirmed in two multiple regression analyses with SC and DSST as the dependent variables. Higher baseline, younger age, and successful taper status (off BZ) were selected as significant independent predictors of SC and DSST scores. In summary, cognitive functions improved for many long-term BZ users after discontinuing their BZ intake.

Trazodone and valproate in patients discontinuing long-term benzodiazepine therapy: effects on withdrawal symptoms and taper outcome.

Recent uncontrolled research suggested that trazodone and sodium valproate may be helpful in benzodiazepine (BZ) discontinuation. We therefore undertook a double-blind study to assess whether trazodone and valproate, as compared to placebo, would attenuate withdrawal and facilitate discontinuation in BZ-dependent patients with a minimum of 1 year daily BZ use. Seventy-eight patients, taking a mean dose of 19+/-17 mg/day of diazepam (or its equivalent), were stabilized for several weeks on their BZ (16 diazepam, 25 lorazepam, 37 alprazolam) and then for 1-2 weeks, pretreated with trazodone, sodium valproate or placebo before being tapered at 25% per week. All treatments were continued for 5 weeks post-taper. BZ-free status was assessed after 5 and 12 weeks post-taper. Neither trazodone nor valproate had any significant effect on withdrawal severity. Peak physician withdrawal checklist change from baseline to peak severity was 16.4 for trazodone, 18.04 sodium valproate and 18.24 placebo (F = 0.10; NS). Taper success rates were significantly effected by both active agents at the 5-week, but not 12-week, assessment. At 5 weeks post-taper, 79% of sodium valproate and 67% of trazodone, but only 31% of placebo patients were BZ-free (chi2 = 7.34; df 2; P<0.03). Major adverse events for trazodone were sedation and dry mouth, and for valproate, diarrhea, nausea and headaches.

Fractionated administration of high-dose cyclophosphamide: influence on dose-dependent changes in pharmacokinetics and metabolism.

PURPOSE: The alkylating agent cyclophosphamide (CP) is a prodrug that is metabolized to both cytotoxic and inactive compounds. We have previously shown that following dose escalation from conventional-dose (CD) to high-dose (HD) levels; the fraction of the dose cleared by bioactivation is significantly decreased (66% versus 48.5%) in favor of inactivating elimination pathways when the HD is given as a single 1-h infusion. Based on the concept of bioactivating enzyme saturation with increasing doses, we investigated the influence of fractionated application of HD-CP on dose-dependent changes in metabolism. PATIENTS AND METHODS: Plasma concentrations of CP (measured by high-performance liquid chromatography, HPLC) and urinary concentrations of CP and its major metabolites (quantified by [31P]-nuclear magnetic resonance spectroscopy; [31P]-NMR spectroscopy), were determined in four patients with high-risk primary breast cancer who received adjuvant chemotherapy including both CD-CP (500 mg/ m2 infused over 1 h) and split HD-CP (50 mg/kg infused over 1 h on each of 2 consecutive days (d): d1 and d2. RESULTS: (Data are given as mean values for CD and d1/d2 of HD, respectively). Systemic clearance (CL) of CP was similar during CD and d1 of HD, but significantly increased on d2 of HD (CL: 83 and 78/115 ml/min; P < 0.01 for d1 versus d2). The latter was translated into an increase in formation CL of both active (+ 16.4 ml/min) and inactive metabolites (+ 17.6 ml/ min) and reflects autoinduction of metabolism. As compared with CD-CP, no statistically significant decrease was observed in the relative contribution of bioactivation CL to overall CL during both days of HD (63% versus 57%/53%). Recovery of intact CP in 24-h urine corresponded to 24%, 29%, 22% of the dose (P < 0.05 for d1 versus d2 of HD). CONCLUSIONS: Following dose escalation of CP, dividing the high dose over 2 days instead of one single infusion may favorably impact the metabolism of CP in terms of bioactivation. In addition, on day 2 of a split regimen, renal elimination of CP is decreased, which implies that more drug is available for metabolism.

Efficacy and safety of fluoxetine in treating bipolar II major depressive episode.

As many as 45% of patients with major depressive episode also meet DSM-IV criteria for bipolar II (BP II) disorder. Although some clinicians advocate using a mood stabilizer in treating BP II depression, antidepressant monotherapy has been less well studied in this disorder. As part of a prospective, placebo-controlled, relapse-prevention study in 839 patients, the efficacy and safety of short- and long-term fluoxetine treatment in patients with BP II major depression compared with patients with unipolar (UP) major depression was retrospectively examined. Eighty-nine BP II patients (mean age, 41+/-11 years) were compared with 89 age- and gender-matched UP patients and with 661 unmatched UP patients (mean age, 39+/-11 years). All received short-term fluoxetine therapy at 20 mg daily for up to 12 weeks. Complete remission was defined as a final Hamilton Rating Scale for Depression score < or = 7 by week 9 that was then maintained for 3 additional weeks. Remitted patients were then randomly assigned to receive double-blind treatment with one of the following: (1) fluoxetine 20 mg daily for 52 weeks; (2) fluoxetine for 38 weeks, then placebo for 14 weeks; (3) fluoxetine for 14 weeks, then placebo for 38 weeks; or (4) placebo for 52 weeks. Antidepressant efficacy was similar in BP and UP patients during short-term therapy. Discontinuation for lack of efficacy was lower in BP II (5%) than in UP (12%) patients (p = not significant [NS]), whereas dropouts for adverse events were similar in BP II (11%) and UP (9%) patients. During long-term relapse-prevention therapy, relapse rates were similar in BP II and UP patients (p = NS). During short-term fluoxetine therapy, three BP II (3.8%) versus no matched UP (p = NS) and 0.3% unmatched UP (p = 0.01) patients had a "manic switch." During long-term fluoxetine therapy, one (2%) BP II and three (1%) unmatched UP patients (one taking placebo) had a manic switch (p = NS). In conclusion, fluoxetine may be a safe and effective antidepressant monotherapy for the short-term treatment of BP II depression with a relatively low manic switch rate. Fluoxetine may also be effective in relapse-prevention therapy in patients with BP II disorder.

The spectrum of generalised anxiety in clinical practice: the role of short-term, intermittent treatment.

BACKGROUND: DSM-IV generalised anxiety disorder (GAD) has a high lifetime prevalence, but subthreshold anxiety states are even more common, particularly in family practice. METHOD: Generalized anxiety is conceptualised as a spectrum of disorders, with transient anxiety at one end and GAD at the other. RESULTS: Based on long-term experience with family practice patients, the authors suggest that most anxious patients, wherever on this continuum they are placed, could be treated with short-term, possibly intermittent, rather than chronic anxiolytic therapy. Data are presented which show that 50% of chronic GAD patients are only in need of such short-term intermittent therapy. CONCLUSIONS: Further clinical research is needed to refine short-term, intermittent treatments for anxiety spectrum disorders, to make effective treatments available to those suffering from anxiety but falling short of diagnostic criteria for GAD, and to target more effectively the different treatment strategies.

Benzodiazepine dependence and withdrawal: a review of the syndrome and its clinical management.

The treatment of anxiety has evolved through various phases. Currently, there is a growing recognition that anxiety disorders are frequently chronic and/or recurrent. There is also less optimism than a decade ago that benzodiazepines will be replaced by alternative agents that are not active at the benzodiazepine receptor. Consequently, the understanding and management of benzodiazepine dependence and withdrawal continue to be of some clinical importance. This article briefly reviews the withdrawal syndrome and the pharmacological and patient variables that contribute to it. It then summarizes the various approaches to managing benzodiazepine dependence and withdrawal.

Pleiotropic phenotype of acetyl-CoA-carboxylase-defective yeast cells--viability of a BPL1-amber mutation depending on its readthrough by normal tRNA(Gln)(CAG).

The Saccharomyces cerevisiae gene BPL1 encodes the enzyme biotin:protein ligase (BPL), which is required for acetyl-CoA carboxylase (ACC) holoenzyme formation. Disruption of one of the two BPL1 alleles present in diploid cells results, upon sporulation, in a 2+:2(0) segregation of cell viability, with none of the two viable spores being BPL1 negative. In contrast to BPL1 deletants, BPL1 base-substitution mutants are potentially viable and may be isolated as long-chain-fatty-acid-requiring auxotrophs. In addition to ACC pyruvate carboxylase and an additional biotin-containing protein of unknown function fail to be biotinylated in BPL1-defective yeast mutants. In this study, one of these mutants, bpl1-C25/17, is shown to contain an amber stop codon at position 151 of the 689-amino-acid BPL sequence. In bpl1-C25/17 cells, de novo fatty acid synthesis is almost absent (< 2% of the wild type), while very-long-chain fatty acid (VLCFA) synthesis and, to some extent, medium-long-chain fatty acid elongation are still active. Hence, endogenous malonyl-CoA synthesis is reduced but not abolished by the translational stop mutation. A low rate of intact-BPL synthesis is accomplished in the mutant by occasional readthrough of the bpl1-C25/17 UAG nonsense triplet by normal yeast tRNA(Gln)(CAG). Correspondingly, ACC biotinylation is severely reduced though not completely absent in the two bpl1 mutants studied in this work. Residual BPL1 expression in bpl1-C25/17 cells is increased to a level allowing wild-type-like growth by transformation with high copy numbers of either the wild-type tRNA(Gln)(CAG) or the mutant bpl1-C25/17 genes. It is concluded that the lethality of BPL1 deletants is due to the lack of malonyl-CoA-dependent VLCFA synthesis and that the viability of distinct ACC-defective point mutants is due to their maintenance of a critical level of malonyl-CoA and, hence, VLCFA production. The residual capacity of malonyl-CoA synthesis, though, is inadequate to allow cytoplasmic bulk de novo fatty acid synthesis, nor does it support mutant growth on 13:0 as the only dietary fatty acid. ACC-defective mutants are respiratory deficient, which is attributed to the failure of mitochondrial fatty acid synthesis. Since lipoic acid levels of ACC1 and BPL1 mutants are essentially normal, an unknown product of mitochondrial fatty acid synthesis appears to be critically reduced in malonyl-CoA-deficient yeast cells.

A novel phosphopantetheine:protein transferase activating yeast mitochondrial acyl carrier protein.

In Saccharomyces cerevisiae, the low molecular weight acyl carrier protein (ACP) of mitochondrial type II fatty acid synthase (FAS) and the cytoplasmic type I FAS multienzyme contain 4'-phosphopantetheine as a prosthetic group. Sequence alignment studies with the recently isolated phosphopantetheine:protein transferase (PPTase), Ppt1p, from Brevibacterium ammoniagenes revealed the yeast open reading frame, YPL148C, as a potential PPTase gene (25% identical and 43% conserved amino acids). In accordance with this similarity, pantetheinylation of mitochondrial ACP was lost upon disruption of YPL148C. In contrast, biosynthesis of cytoplasmic holo-FAS remained unaffected by this mutation. According to these characteristics, the newly identified gene was designated as PPT2. Similar to ACP null mutants, cellular lipoic acid synthesis and, hence, respiration were abolished in PPT2 deletants. ACP pantetheinylation, lipoic acid synthesis, and respiratory competence were restored upon transformation of PPT2 mutants with cloned PPT2 DNA. In vitro, holo-ACP synthesis was achieved by incubating apo-ACP with coenzyme A in the presence of purified Ppt2p. The homologous yeast enzyme could be replaced, in this assay, by the ACP synthase (EC 2.7.8.7) of Escherichia coli but not by the type I FAS-specific PPTase of B. ammoniagenes, Ppt1p. These results conform with the inability of Ppt2p to activate the cytoplasmic type I FAS complex of yeast.

The effect of personality on withdrawal severity and taper outcome in benzodiazepine dependent patients.

BACKGROUND: Personality psychopathology exerts a significant and independent effect on the course of benzodiazepine (BZ) discontinuation, worsening the subjective severity of withdrawal symptoms and significantly increasing the occurrence of early taper failures. METHOD: One hundred and seventy-one patients participating in a BZ discontinuation programme were administered several personality measures prior to taper. Patients were stabilized for 3 weeks at their baseline BZ dosage and then tapered off 25% per week over 4 weeks, with the option to extend up to 6 weeks if necessary. RESULTS: High levels of passivity and dependency as assessed by the MMPI Dependence subcluster, and at a trend level high Eysenck Neuroticism and high TPQ Harm Avoidance contributed significantly to the prediction of benzodiazepine withdrawal severity. Though there was a high correlation between personality measures, psychopathology and adjusted BZ dose, the effects of personality on withdrawal severity was significant, particularly in the initial phases of BZ taper, when taper severity was still relatively mild. CONCLUSIONS: These findings indicate that clinical decisions on how to manage BZ tapering should be guided by personality assessments, in addition to the usual considerations of BZ dosage, residual psychopathology, duration of treatment, etc. The potential for difficulty with discontinuation related to personality traits should be one of the factors weighted in the risk-benefit assessment made in the planning of benzodiazepine treatment for patients with anxious symptomatology.