Redesign of the coenzyme specificity of a dehydrogenase by protein engineering

Directed mutagenesis and molecular modelling have been used to identify a set of amino-acid side chains in glutathione reductase that confer specificity for the coenzyme NADP+. Systematic replacement of these amino acids, all of which occur in a 'fingerprint' structural motif in the NADP+-binding domain, leaves the substrate specificity unchanged but converts the enzyme into one displaying a marked preference for the coenzyme NAD+.

Alginate synthesis by Pseudomonas aeruginosa: a key pathogenic factor in chronic pulmonary infections of cystic fibrosis patients

Pulmonary infection by mucoid, alginate-producing Pseudomonas aeruginosa is the leading cause of mortality among patients suffering from cystic fibrosis. Alginate-producing P. aeruginosa is uniquely associated with the environment of the cystic fibrosis-affected lung, where alginate is believed to increase resistance to both the host immune system and antibiotic therapy. Recent evidence indicates that P. aeruginosa is most resistant to antibiotics when the infecting cells are present as a biofilm, as they appear to be in the lungs of cystic fibrosis patients. Inhibition of the protective alginate barrier with nontoxic compounds targeted against alginate biosynthetic and regulatory proteins may prove useful in eradicating P. aeruginosa from this environment. Our research has dealt with elucidating the biosynthetic pathway and regulatory mechanism(s) responsible for alginate synthesis by P. aeruginosa. This review summarizes reports on the role of alginate in cystic fibrosis-associated pulmonary infections caused by P. aeruginosa and provides details about the biosynthesis and regulation of this exopolysaccharide.

Early disruption of the mother-infant relationship: effects on brain plasticity and implications for psychopathology

Early environmental manipulations can impact on the developing nervous system, contributing to shape individual differences in physiological and behavioral responses to environmental challenges. In particular, it has been shown that disruptions in the mother-infant relationship result in neuroendocrine, neurochemical and behavioural changes in the adult organism, although the basic mechanisms underlying such changes have not been completely elucidated. Recent data suggest that neurotrophins might be among the mediators capable of transducing the effects of external manipulations on brain development. Nerve growth factor and brain-derived neurotrophic factor are known to play a major role during brain development, while in the adult animal they are mainly responsible for the maintenance of neuronal function and structural integrity. Changes in the levels of neurotrophic factors during critical developmental stages might result in long-term changes in neuronal plasticity and lead to increased vulnerability to aging and to psychopathology.

The incidence of aspiration associated with the laryngeal mask airway: a meta-analysis of published literature

STUDY OBJECTIVE

To determine the incidence of pulmonary aspiration with the laryngeal mask airway (LMA).

DESIGN

A meta-analysis of all published literature on the LMA to September 1993.

MEASUREMENTS AND MAIN RESULTS

All 547 publications were reviewed and coded, and those observational studies in which the LMA was the main form of airway management were analyzed. Pulmonary aspiration was defined as either the presence of bilious secretions or particulate matter in the tracheobronchial tree or, if bronchoscopy was not performed, a postoperative chest radiograph with infiltrates present on preoperative chest radiograph of physical examination. In the study population, there were 3 cases of aspiration in 12,901 patients, and when combined with four independent reports excluded from the detailed analysis, this gave a final incidence of 2 in 10,000. Ten confirmed pulmonary aspiration events from published case reports showed that most cases had one or more predisposing factors. No death of permanent disability occurred.

CONCLUSIONS

The evidence to date suggests that the pulmonary aspiration with the LMA is uncommon and comparable to that for outpatient anesthesia with the face mask and tracheal tube. Meticulous attention to selection of low-risk patients and appropriate operative procedures and avoidance of light anesthesia should reduce the incidence even further.

There's more to self-esteem than whether it is high or low: the importance of stability of self-esteem

Study 1 examined the extent to which stability and level of self-esteem predicted cognitive and emotional reactions to interpersonal feedback. Among high self-esteem individuals, instability was associated with acceptance and positive emotions following positive feedback but to rejection and defensiveness following negative feedback. Among low self-esteem individuals, instability was unrelated to reactions to positive feedback but was related to less defensiveness and greater acceptance of negative feedback. Study 2 examined the extent to which variability and importance of specific self-evaluations were associated with instability of global self-esteem. Discussion focused on the roles of level and stability of self-esteem in reactions to evaluations and on the nature of self-esteem instability.

Pathway engineering for the production of aromatic compounds in Escherichia coli

Glucose is the preferred substrate for certain fermentation processes. During its internalization and concomitant formation of glucose-6-phosphate through the glucose phosphotransferase system (PTS), one molecule of phosphoenolpyruvate (PEP) is consumed. Together with erythrose 4-phosphate (E4P), PEP is condensed to form 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP), the first intermediate of the common segment of the aromatic pathway. From this metabolic route, several commercially important aromatic compounds can be obtained. We have selected Escherichia coli mutants that can transport glucose efficiently by a non-PTS uptake system. In theory, this process should increase the availability of PEP for other biosynthetic reactions. Using these mutants, in a background where the DAHP synthase (the enzyme that catalyzes the condensation of PEP and E4P into DAHP) was amplified, we were able to show that at least some of the PEP saved during glucose transport, can be redirected into the aromatic pathway. This increased carbon commitment to the aromatic pathway was enhanced still further upon amplification of the E. coli tktA gene that encodes for a transketolase involved in the biosynthesis of E4P.

Molecular analysis of an allozyme cline: alcohol dehydrogenase in Drosophila melanogaster on the east coast of North America

Clines may either be selectively maintained or be the by-product of nonadaptive processes related to population structure and history. Drosophila melanogaster populations on the east coast of North America show a latitudinal cline in the frequencies of two common electrophoretically distinguishable alleles at the alcohol dehydrogenase locus (Adh), designated Adh-S and Adh-F. This cline may either be adaptive or an artifact of a possible recent dual founding of North American D. melanogaster populations in which frequencies of Adh alleles differed between founder populations. By means of a high resolution restriction-mapping technique, we studied the distribution of 113 haplotypes derived from 44 polymorphic DNA markers within the Adh region in 1533 individuals from 25 populations throughout the cline. We found significant clinal differentiation at the polymorphism determining the mobility-difference causing amino acid replacement between Adh-F and Adh-S alleles. Hitchhiking was limited, despite extensive linkage disequilibrium, and other sites did not vary clinally. Such a pattern of differentiation implies that selection is responsible for the cline. To investigate whether selection acts only on the Adh-F/S site, we performed a "selective equivalence" test under the assumption that all variability within the specified allelic class is selectively neutral. This revealed selective equivalence among Adh-S-bearing haplotypes, whose frequencies showed no differentiation throughout the cline, implying high levels of frequency-homogenizing gene flow. Geographical heterogeneity among Adh-F-bearing haplotypes implied the action of selection on one or more additional variants in linkage disequilibrium with Adh-F. In a further study of a subset of the data (n = 1076 from 18 populations), we found a combined insertion/deletion polymorphism, designated delta 1, located in the 5' adult intron and in linkage disequilibrium with Adh-F, to show more marked clinal variation than Adh-F/S. Although the unequivocal identification of the precise target(s) of selection requires further study, we suggest that clinal selection may be acting epistatically on the Adh-F/S and delta 1 polymorphisms.

Insertion of beta-satellite repeats identifies a transmembrane protease causing both congenital and childhood onset autosomal recessive deafness

Approximately 50% of childhood deafness is caused by mutations in specific genes. Autosomal recessive loci account for approximately 80% of nonsyndromic genetic deafness. Here we report the identification of a new transmembrane serine protease (TMPRSS3; also known as ECHOS1) expressed in many tissues, including fetal cochlea, which is mutated in the families used to describe both the DFNB10 and DFNB8 loci. An 8-bp deletion and insertion of 18 monomeric (approximately 68-bp) beta-satellite repeat units, normally present in tandem arrays of up to several hundred kilobases on the short arms of acrocentric chromosomes, causes congenital deafness (DFNB10). A mutation in a splice-acceptor site, resulting in a 4-bp insertion in the mRNA and a frameshift, was detected in childhood onset deafness (DFNB8). This is the first description of beta-satellite insertion into an active gene resulting in a pathogenic state, and the first description of a protease involved in hearing loss.

Insertion of the laryngeal mask airway--a prospective study of four techniques

The standard insertion technique (ST 0) for laryngeal mask airway insertion was compared to three alternative techniques in 120 patients. The alternative techniques included insertion using the standard approach, but with the cuff either semi-inflated (ST 0.5) or fully inflated (ST 1.0), and a non-standard approach using a back-to-front technique (like a Guedel airway) and with the cuff fully deflated (T 180). Successful insertion was judged by fibreoptic positioning (P < 0.02) and that confirmed that the ST 0 and T 180 were superior to ST 0.5 and ST 1.0 in terms of fibreoptic positioning (P < 0.02) and that insertion with the cuff deflated (ST 0 and T 180) resulted in fewer insertion failures than with the cuff inflated (ST 0.5 and ST 1.0) (P < 0.05). Insertion with the LMA back-to-front with the cuff deflated produced similar fibreoptic and functional results to the standard technique. In 23%, however, there was some residual rotation of 25-90% to the coronal plane.

High osmolarity is a signal for enhanced algD transcription in mucoid and nonmucoid Pseudomonas aeruginosa strains

Chronic lung infection with mucoid, alginate-producing strains of Pseudomonas aeruginosa is a major cause of mortality in cystic fibrosis (CF) patients. Transcriptional activation of the P. aeruginosa algD gene, which encodes GDPmannose dehydrogenase, is essential for alginate synthesis. Activation of algD is dependent on the product of the algR gene. Sequence homology between the P. aeruginosa algR gene and the Escherichia coli ompR gene, which regulates the cellular response to changes in osmolarity of the growth medium, together with the abnormally high levels of Na+ and Cl- in respiratory tract fluid in CF patients suggested that high osmolarity in the lung of the CF patient might be a signal contributing to the induction of alginate synthesis (mucoidy) in infecting P. aeruginosa. In both mucoid and nonmucoid P. aeruginosa strains (containing a functional algR gene), transcriptional activation of algD increased as the osmolarity of the culture medium increased. The increased activation of algD at high osmolarity was not in itself sufficient to induce alginate synthesis in nonmucoid strains, however, suggesting that other environmental factors are involved in full activation of the alginate genes. The targets of AlgR and OmpR, the algD promoter and the ompC and ompF promoters, respectively, were found to have appreciable sequence homology in the -60 to -110 regions. In E. coli, OmpR was capable of activating the algD promoter nearly as well as AlgR, but in both cases, activation occurred only under conditions of high osmolarity.

Risk factors of Pneumocystis pneumonia in solid organ recipients in the era of the common use of posttransplantation prophylaxis

Pneumocystis pneumonia (PCP) in solid organ transplant (SOT) recipients becomes rare in the immediate posttransplantation period thanks to generalized prophylaxis. We aimed to identify the predictive factors for PCP in the era of universal prophylaxis and to propose a strategy for preventing PCP beyond the first year after transplantation. In a retrospective case-control study, 33 SOT cases with PCP diagnosed between 2004 and 2010 were matched with two controls each to identify risk factors for PCP by uni- and multivariate analysis. All the patients benefited from 6 months of posttransplantation trimethoprim-sulfamethoxazole prophylaxis. Most PCP in SOT patients occurred during the second year posttransplantation (33%). By univariate analysis, age, nonuse of tacrolimus, total and CD4 lymphocyte counts, gamma-globulin concentration and cytomegalovirus (CMV) infection appeared to be PCP risk factors. In the final multivariate analysis, age (adjusted odds ratio [OR] 3.7, 95% confidence interval [CI]: 1.3-10.4), CMV infection (OR: 5.2, 95% CI: 1.8-14.7) and total lymphocyte count (OR: 3.9, 95% CI: 1.4-10.7) were found to be independently associated with PCP. The second year posttransplantation appeared to be the new period of highest risk of PCP. Age, CMV viremia and lymphocytes were the most pertinent predictive criteria to evaluate the risk of PCP in clinical practice.

Simultaneous detection of gastrointestinal pathogens with a multiplex Luminex-based molecular assay in stool samples from diarrhoeic patients

We have evaluated the multiplex molecular method xTAG(®) Gastrointestinal Panel (GPP) for detecting pathogens in stool samples of diarrhoeic patients. We collected 440 samples from 329 patients (male:female ratio of 1.2:1), including 102 immunosuppressed adults, 50 immunosuppressed children, 56 children attending the neonatal unit and 121 children attending the emergency unit. Of these, 176 samples from 162 patients were xTAG(®) GPP positive (102 viruses, 61 bacteria and 13 parasites) and the assay was more sensitive than the conventional test for detecting rotavirus (p <0.01), noroviruses (p <0.0001), Salmonella spp. (p <0.001), Campylobacter spp. (p <0.001) and toxigenic Clostridium difficile (p 0.005). The predominant pathogens were viruses (23.2%), with rotavirus (15.9%) being the most common. Bacterial agents were detected in 13.9%; the most common was Salmonella spp. (4.8%). Parasites were detected in 2.9%; Cryptosporidium spp. (2%) was the most common. There were 31 co-infections (7% of samples), involving two pathogens in 23 (5.2%) and three pathogens in eight (1.8%) samples. There were 113 (92.6%) positive samples from the children attending the emergency unit, 25 (17%) positive samples from immunosuppressed adults, 22 (25.3%) positive samples from immunosuppressed children and 16 (19%) positive samples from children attending the neonatal unit. The low turnaround time and technical hands-on time make this multiplex technique convenient for routine use. Nevertheless, conventional bacterial culture and parasitological stool examination are still required to detect other pathogens in specific cases and to determine susceptibility to antibiotics.

Comparison between two amplification sets for molecular diagnosis of toxoplasmosis by real-time PCR

PCR is now commonly applied to the diagnosis of toxoplasmosis. Although several methods are available, comparative studies are few, making it difficult to compare the performance of each technique. We compared the sensitivities of two real-time PCR assays through a prospective study on fetuses, neonates, and immunocompromised patients and on the ocular diagnosis of toxoplasmosis. The first system targeted the widely used B1 gene (GenBank accession number AF179871) while the second (RE) targeted a more recently described sequence repeated roughly 200 to 300 times (GenBank accession number AF146527). We demonstrated that molecular diagnosis requires the duplication of PCR assays, especially with the B1 system, as only one PCR was positive in 33.3% of cases. Our study showed that the RE target was more sensitive for all biological samples (amniotic fluid, placenta, aqueous humor, whole blood, and cerebrospinal and bronchoalveolar fluids) and significantly improved the performance of the diagnosis of toxoplasmosis. Taking into consideration all clinical samples, the mean gain in the crossing point value was 4.2 +/- 1.7 cycles and was even more significant for amniotic fluid (5.8 +/- 1.7 cycles).

The tissue distribution of the human beta3-adrenoceptor studied using a monoclonal antibody: direct evidence of the beta3-adrenoceptor in human adipose tissue, atrium and skeletal muscle

OBJECTIVE

To develop a monoclonal antibody that recognises an epitope of the native beta3-adrenoceptor expressed on the extracellular surface of human cells and tissues.

DESIGN

A high affinity monoclonal antibody, Mab72c, was raised against the human beta3-adrenoceptor expressed on a transfected mammalian cell line.

RESULTS

In CHO (Chinese hamster ovary) cells transfected with beta3-adrenoceptor cDNA, antibody labelling was found to be proportional to receptor density measured by the binding of the radiolabelled beta-adrenoceptor antagonist, [125I]-iodocyanopindolol. The use of Mab 72c has demonstrated the expression of the beta3-adrenoceptor in a variety of human tissues, including gall bladder, prostate and colon, where a mRNA signal had been detected previously. This study also provides the first direct demonstration of the expression of beta3-adrenoceptors in human skeletal muscle, atrium and adipose tissue.

CONCLUSION

The development of this antibody represents an important addition to the armentarium of reagents that are available to study the localisation of beta3-adrenoceptors in human tissues.

The crystal structure of Escherichia coli class II fructose-1, 6-bisphosphate aldolase in complex with phosphoglycolohydroxamate reveals details of mechanism and specificity

The structure of a class II fructose-1,6-bisphosphate aldolase in complex with the substrate analogue and inhibitor phosphoglycolohydroxamate (PGH) has been determined using X-ray diffraction terms to a resolution of 2.0 A (1 A=0.1 nm). The crystals are trigonal, space group P3121 with a=b=78.24 A, c=289.69 A. The asymmetric unit is a homodimer of (alpha/beta)8 barrels and the model has refined to give R-work 19.2 %, R-free (based on 5 % of the data) 23.0 %. PGH resembles the ene-diolate transition state of the physiological substrate dihydroxyacetone phosphate. It is well ordered and bound in a deep polar cavity at the C-terminal end of the (alpha/beta)8 barrel, where it chelates the catalytic zinc ion using hydroxyl and enolate oxygen atoms. Trigonal bipyramidal coordination of the zinc ion is completed by three histidine residues. The complex network of hydrogen bonds at the catalytic centre is required to organise the position of key functional groups and metal ion ligands. A well-defined monovalent cation-binding site is observed following significant re-organisation of loop structures. This assists the formation of a phosphate-binding site on one side of the barrel that tethers PGH in the catalytic site. The positions of functional groups of substrate and putative interactions with key amino acid residues are identified. Knowledge of the complex structure complements the results of spectroscopic and site-directed mutagenesis studies, and contributes to our understanding of the mechanism and substrate specificity of this family of enzymes. A reaction mechanism distinct from that proposed for other class II aldolases is discussed. The results suggest that the class II aldolases should be sub-divided into two groups on the basis of both distinct folds and mechanism.

A randomized controlled trial comparing the cuffed oropharyngeal airway and the laryngeal mask airway in spontaneously breathing anesthetized adults

BACKGROUND

The cuffed oropharyngeal airway (COPA), a modified Guedel airway, was compared with the laryngeal mask airway (LMA) during spontaneous breathing anesthesia. Specifically examined were ease of use, physiologic tolerance, and the frequency of problems.

METHODS

Adult patients consented to random (2:1) assignment to either COPA (n = 302) or LMA (n = 151) for airway management during anesthesia with propofol, nitrous oxide, and oxygen.

RESULTS

Ease of insertion was similar, but the first-time successful insertion rate was higher with the LMA (COPA, 81% compared with LMA, 89%; P = 0.05). More brief manipulations (head tilt, chin lift, jaw thrust) were reported in the COPA group (average total number of manipulations: COPA, 1.1 +/- 1.6 compared with LMA, 0.1 +/- 0.2; P < 0.001). Continuous airway support was used more frequently in the COPA group (COPA, 30% compared with LMA, 0%; P < 0.0005). The incidences of aspiration, regurgitation, laryngospasm, wheezing, succinylcholine administration, oxygen saturation (SpO2) < 92%, failed use, and minor intraoperative problems were similar. When the airways were removed, blood was detected on the COPA less frequently than on the LMA (COPA, 5.8% compared with LMA, 15.3%; P = 0.001). The incidence of early and late sore throat was greater with the LMA (early: COPA, 4.7% compared with LMA, 21.9% [P = 0.001]; late: COPA, 8.4% compared with LMA, 16.1%; P = 0.01). The LMA did better than the COPA when anesthetists analyzed the technical aspects of the two devices.

CONCLUSIONS

Although the COPA and LMA are equivalent devices in terms of physiologic alterations and overall clinical problems associated with their use, the LMA was associated with a higher first-time insertion rate and fewer manipulations, suggesting that it is easier to use. The COPA was associated with less blood on the device and fewer sore throats, suggesting it may cause less pharyngeal trauma. Ultimately, both devices were similar in establishing a safe and effective airway for spontaneously breathing anesthetized adults.

The crystal structure of a class II fructose-1,6-bisphosphate aldolase shows a novel binuclear metal-binding active site embedded in a familiar fold

BACKGROUND

[corrected] Aldolases catalyze a variety of condensation and cleavage reactions, with exquisite control on the stereochemistry. These enzymes, therefore, are attractive catalysts for synthetic chemistry. There are two classes of aldolase: class I aldolases utilize Schiff base formation with an active-site lysine whilst class II enzymes require a divalent metal ion, in particular zinc. Fructose-1,6-bisphosphate aldolase (FBP-aldolase) is used in gluconeogenesis and glycolysis; the enzyme controls the condensation of dihydroxyacetone phosphate with glyceraldehyde-3-phosphate to yield fructose-1,6-bisphosphate. Structures are available for class I FBP-aldolases but there is a paucity of detail on the class II enzymes. Characterization is sought to enable a dissection of structure/activity relationships which may assist the construction of designed aldolases for use as biocatalysts in synthetic chemistry.

RESULTS

The structure of the dimeric class II FBP-aldolase from Escherichia coli has been determined using data to 2.5 A resolution. The asymmetric unit is one subunit which presents a familiar fold, the (alpha/beta)8 barrel. The active centre, at the C-terminal end of the barrel, contains a novel bimetallic-binding site with two metal ions 6.2 A apart. One ion, the identity of which is not certain, is buried and may play a structural or activating role. The other metal ion is zinc and is positioned at the surface of the barrel to participate in catalysis.

CONCLUSIONS

Comparison of the structure with a class II fuculose aldolase suggests that these enzymes may share a common mechanism. Nevertheless, the class II enzymes should be subdivided into two categories on consideration of subunit size and fold, quaternary structure and metal-ion binding sites.

Improving production of aromatic compounds in Escherichia coli by metabolic engineering

The efficiency of conversion of raw material to product is a major factor controlling the commercial viability of large-scale fermentation processes for the production of metabolites. Traditional approaches to developing microbial strains for metabolite overproduction have relied on amplifying only the enzymatic steps within the specific biosynthetic pathway of a desired product. While this approach has generally been successful for reaching high product concentrations and yields, further improvements (and hence reduced manufacturing cost) can only be achieved by redirecting carbon flux from central metabolism to the product-forming pathway. Such manipulation of central metabolic pathways promises to deliver a new generation of metabolite-producing microorganisms.

A nonsense mutation of the human luteinizing hormone receptor gene in Leydig cell hypoplasia

Leydig cell hypoplasia (LCH) is a form of male pseudohermaphroditism in which Leydig cell differentiation and testosterone production are impaired. This report describes the first case of a nonsense mutation (A1635C) in exon 11 of the human luteinizing hormone receptor (hLHR) gene in two sisters with LCH. This mutation causes loss of function of the receptor by introducing a stop codon at residue 545 in transmembrane helix 5 of the hLHR. Surface expression of the truncated hLHR (hLHR-t545) in human embryonic kidney cells stably transfected with cDNA encoding hLHR-t545 was diminished compared to the wild-type hLHR and hCG-induced cAMP accumulation was impaired. These results establish that single base mutations in exon 11 of the hLHR gene can produce inactivation as well as activation of the hLHR. Furthermore, they demonstrate that functional domains between transmembrane helix 5 and the C-terminal cytoplasmic tail of the hLHR are required for normal cell surface expression of the receptor and signal transduction.

Haplotypic divergence coupled with lack of diversity at the Arabidopsis thaliana alcohol dehydrogenase locus: roles for both balancing and directional selection?

We designate a region of the alcohol dehydrogenase locus (Adh) of the weedy crucifer, Arabidopsis thaliana, as "hypervariable" on the basis of a comparison of sequences from ecotypes Columbia and Landsberg. We found eight synonymous and two replacement mutations in the first 262 nucleotides of exon 4, and an additional two mutations in the contiguous region of intron 3. The rest of the sequence (2611 bp) has just three mutations, all of them confined to noncoding regions. Our survey of the hypervariable region among 37 ecotypes of A. thaliana revealed two predominant haplotypes, corresponding to the Columbia and Landsberg sequences. We identified five additional haplotypes and 4 additional segregating sites. The lack of haplotype diversity is presumably in part a function of low rates of recombination between haplotypes conferred by A. thaliana's tendency to self-fertilize. However, an analysis in 32 ecotypes of 12 genome-wide polymorphic markers distinguishing Columbia and Landsberg ecotypes indicated levels of outcrossing sufficient at least to erode linkage disequilibrium between dispersed markers. We discuss possible evolutionary explanations for the coupled observation of marked divergence within the hypervariable region and a lack of haplotype diversity among ecotypes. The sequence of the region for closely related species argues against the possibility that one allele is the product of introgression. We note (1) that several loss of function mutations (both naturally and chemically induced) map to the hypervariable region, and (2) the presence of two amino acid replacement polymorphisms, one of which causes the mobility difference between the two major classes of A. thaliana Adh electrophoretic alleles. We argue that protein polymorphism in such a functionally significant part of the molecule may be subject to balancing selection. The observed pattern of extensive divergence between the alleles is consistent with this explanation because balancing selection on a particular site maintains linked neutral polymorphisms at intermediate frequencies.

Prophylactic antibiotic use in transurethral prostatic resection: a meta-analysis

PURPOSE

We reviewed the efficacy of antibiotic prophylaxis in men undergoing transurethral prostatic resection, a clean contaminated procedure.

MATERIALS AND METHODS

We systematically reviewed randomized controlled trials of antibiotic prophylaxis for transurethral prostatic resection with a meta-analysis of the results. We identified 32 randomized controlled trials with 4,260 participants examining the postoperative bacteriuria incidence. An 8-trial subset with 1,979 participants examined postoperative septicemia occurrence.

RESULTS

Prophylactic antibiotic use in patients at low risk undergoing transurethral prostatic resection significantly decreased bacteriuria and clinical septicemia incidence. The bacteriuria incidence decreased from 26% to 9.1% (relative risk reduction 65%, 95% confidence interval -56 to -73). The clinical septicemia incidence decreased from 4.4% to 0.7% (relative risk reduction 77%, 95% confidence interval -55 to -88). Effective antibiotic classes included quinolones, cephalosporins, co-trimoxazole and aminoglycosides. Treatment protocols of any duration were effective. Subgroup analysis of cephalosporin based trials indicated that short treatment protocols appeared more effective than single dose protocols. Based on these results if 1,000 patients with sterile urine undergoing transurethral prostatic resection were given prophylactic antibiotics, bacteriuria would be avoided in 175, while septicemia would be prevented in 9 to 20.

CONCLUSIONS

Antibiotic prophylaxis significantly decreases the incidence of bacteriuria and clinical septicemia in men with preoperative sterile urine undergoing transurethral prostatic resection. A significant decrease in bacteriuria incidence can be achieved with a range of antibiotic agents, including quinolones, cephalosporins and co-trimoxazole. Short course antibiotic protocols may be more effective than single dose regimens.

Low doses of dexamethasone can produce a hypocorticosteroid state in the brain

The synthetic glucocorticoid dexamethasone (dex) blocks stress-induced hypothalamic-pituitary-adrenal (HPA) activation primarily at the level of the anterior pituitary because multidrug resistance P-glycoprotein hampers its penetration in the brain. Here, we tested the hypothesis that central components of the HPA axis would escape dex suppression under conditions of potent peripheral glucocorticoid action. We subchronically treated rats with low or high doses of dex. The animals were subjected on the last day of treatment for 30 min to a restraint stressor after which central and peripheral markers of HPA axis activity were measured. Basal and stress-induced corticosterone secretion, body weight gain, adrenal and thymus weight, as well as proopiomelanocortin mRNA in the anterior pituitary were reduced in a dose-dependent manner by dex administered either 5 d sc or 3 wk orally. In the brain, the highest dose dex suppressed CRH mRNA and CRH heteronuclear RNA in the paraventricular nucleus (PVN). However, in the peripherally active low-dose range of dex CRH mRNA and heteronuclear RNA showed resistance to suppression, and CRH mRNA expression in the PVN was in fact enhanced under the long-term treatment condition. In the PVN, c-fos mRNA was suppressed by the highest dose of dex, but this effect showed a degree of resistance after long-term oral treatment. c-fos mRNA responses in the anterior pituitary followed those in PVN and reflect central drive of the HPA axis even if corticosterone responses are strongly reduced. The results support the concept that low doses of dex can create a hypocorticoid state in the brain.

Application of metabolic engineering to improve both the production and use of biotech indigo

A fermentation process was developed for production of indigo from glucose using recombinant Escherichia coli. This was achieved by modifying the tryptophan pathway to cause high-level indole production and adding the Pseudomonas putida genes encoding naphthalene dioxygenase (NDO). In comparison to a tryptophan-over-producing strain, the first indigo-producing strain made less than half of the expected amount of indigo. Severe inactivation of the first enzyme of aromatic biosynthesis, 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase (the aroGfbr gene product), was observed in cells collected from indigo fermentations. Subsequent in vitro experiments revealed that DAHP synthase was inactivated by exposure to the spontaneous chemical conversion of indoxyl to indigo. Indigo production was thereafter improved by increasing the gene dosage of aroGfbr or by increasing substrate availability to DAHP synthase in vivo by either amplifying the tktA (transketolase) gene or inactivating both isozymes of pyruvate kinase. By combining all three strategies for enhancing DAHP formation in the cell, a 60% increase in indigo production was achieved. Metabolic engineering was then further applied to eliminate a byproduct of the spontaneous conversion of indoxyl to indigo, thereby solving a serious problem with the use of bio-indigo in the final denim dyeing application.

Caveolin mediates rapid glucocorticoid effects and couples glucocorticoid action to the antiproliferative program

Many glucocorticoid (Gc) actions are of rapid onset and therefore require acute regulation of intracellular signaling cascades. Integration of diverse extracellular signals requires cross-talk between intracellular pathways, suggesting the existence of nodes for signal interaction, such as the specialized membrane microdomains caveolae. We have identified rapid Gc-dependent phosphorylation of caveolin, and protein kinase B (PKB)/Akt, in the lung epithelial cell line A549 and found this was dependent on src kinases. There was also activation of PKB downstream molecules glycogen synthase kinase-3beta, and mammalian target of rapamycin. Subcellular fractionation colocalized glucocorticoid receptor (GR) and c-src to caveolin-containing membrane fractions. Coimmunoprecipitation studies also identified interactions between GR and caveolin and suggested that the activation function 1 domain within the GR may serve to support an interaction between GR and caveolin. Disruption of lipid raft formation, impairment of caveolin function using dominant-negative caveolin, down-regulation of caveolin-1 using short hairpin RNA or complete ablation of caveolin-1 prevented Gc-induced activation of PKB. Loss of caveolin-1 also prevents Gc activation of glycogen synthase kinase-3beta and mammalian target of rapamycin. In contrast, caveolin interference/down-regulation had no effect on Gc transactivation. Functional analysis of caveolin-1 knockdown and knockout cells identified profound loss of Gc-mediated growth inhibition compared with controls, with a requirement for caveolin in order for Gc to regulate cell cycle progression. Therefore, disruption of caveolae leads to dissociation of Gc action, with impaired induction of PKB activation, and cell growth inhibition, but with negligible effects on Gc transactivation. These observations have implications for understanding the diverse physiological actions of Gc.

A direct comparison of approaches for increasing carbon flow to aromatic biosynthesis in Escherichia coli

Different approaches to increasing carbon commitment to aromatic amino acid biosynthesis were compared in isogenic strains of Escherichia coli. In a strain having a wild-type PEP:glucose phosphotransferase (PTS) system, inactivation of the genes encoding pyruvate kinase (pykA and pykF) resulted in a 3.4 fold increase in carbon flow to aromatic biosynthesis. In a strain already having increased carbon flow to aromatics by virtue of overexpression of the tktA gene (encoding transketolase), the pykA and/or pykf mutations had no effect. A PTS- glucose+ mutant showed a 1.6-fold increase in carbon flow to aromatics compared to the PTS+ control strain. In the PTS- glucose+ host background, overexpression of tktA caused a further 3.7-fold increase in carbon flow, while inactivation of pykA and pykF caused a 5.8-fold increase. When all of the variables tested (PTS-glucose+, pykA, pykF, and overexpressed tktA) were combined in a single strain, a 19.9-fold increase in carbon commitment to aromatic biosynthesis was achieved.