Measuring non-steady-state metabolic fluxes in starch-converting faecal microbiota in vitro.

This paper explores human gut bacterial metabolism of starch using a combined analytical and computational modelling approach for metabolite and flux analysis. Non-steady-state isotopic labelling experiments were performed with human faecal microbiota in a well-established in vitro model of the human colon. After culture stabilisation, [U-13C] starch was added and samples were taken at regular intervals. Metabolite concentrations and 13C isotopomeric distributions were measured amongst other things for acetate, propionate and butyrate by mass spectrometry and NMR. The vast majority of metabolic flux analysis methods based on isotopomer analysis published to date are not applicable to metabolic non-steady-state experiments. We therefore developed a new ordinary differential equation-based representation of a metabolic model of human faecal microbiota to determine eleven metabolic parameters that characterised the metabolic flux distribution in the isotope labelling experiment. The feasibility of the model parameter quantification was demonstrated on noisy in silico data using a downhill simplex optimisation, matching simulated labelling patterns of isotopically labelled metabolites with measured metabolite and isotope labelling data. Using the experimental data, we determined an increasing net label influx from starch during the experiment from 94±1 µmol/l/min to 133±3 µmol/l/min. Only about 12% of the total carbon flux from starch reached propionate. Propionate production mainly proceeded via succinate with a small contribution via acrylate. The remaining flux from starch yielded acetate (35%) and butyrate (53%). Interpretation of 13C NMR multiplet signals further revealed that butyrate, valerate and caproate were mainly synthesised via cross-feeding, using acetate as a co-substrate. This study demonstrates for the first time that the experimental design and the analysis of the results by computational modelling allows the determination of time-resolved effects of nutrition on the flux distribution within human faecal microbiota in metabolic non-steady-state.

Uveitis-like syndrome and iris transillumination after the use of oral moxifloxacin.

OBJECTIVE: To report a newly recognized adverse effect of oral moxifloxacin. DESIGN: Observational case reports. PARTICIPANTS: Five patients who used oral moxifloxacin therapy. MAIN OUTCOME MEASURES: In five patients, a uveitis-like episode followed oral moxifloxacin therapy, afterwards they experienced photophobia. At slitlamp investigation, the patients showed almost complete iris transillumination, not restricted to one sector, and persistent mydriasis of the pupil, with no reaction to light and no near reflex. Follow-up of 3 years in one of the patients showed no change of symptoms. Only in one patient, with a history of anterior uveitis, an anterior chamber tap was positive for herpes simplex genome. Only after the use of moxifloxacin did she experience continuous photophobia. CONCLUSIONS: Iris transillumination and sphincter paralysis is a newly recognized adverse effect of oral moxifloxacin therapy.

Massetolide A biosynthesis in Pseudomonas fluorescens.

Massetolide A is a cyclic lipopeptide (CLP) antibiotic produced by various Pseudomonas strains from diverse environments. Cloning, sequencing, site-directed mutagenesis, and complementation showed that massetolide A biosynthesis in P. fluorescens SS101 is governed by three nonribosomal peptide synthetase (NRPS) genes, designated massA, massB, and massC, spanning approximately 30 kb. Prediction of the nature and configuration of the amino acids by in silico analysis of adenylation and condensation domains of the NRPSs was consistent with the chemically determined structure of the peptide moiety of massetolide A. Structural analysis of massetolide A derivatives produced by SS101 indicated that most of the variations in the peptide moiety occur at amino acid positions 4 and 9. Regions flanking the mass genes contained several genes found in other Pseudomonas CLP biosynthesis clusters, which encode LuxR-type transcriptional regulators, ABC transporters, and an RND-like outer membrane protein. In contrast to most Pseudomonas CLP gene clusters known to date, the mass genes are not physically linked but are organized in two separate clusters, with massA disconnected from massB and massC. Quantitative real-time PCR analysis indicated that transcription of massC is strongly reduced when massB is mutated, suggesting that these two genes function in an operon, whereas transcription of massA is independent of massBC and vice versa. Massetolide A is produced in the early exponential growth phase, and biosynthesis appears not to be regulated by N-acylhomoserine lactone-based quorum sensing. Massetolide A production is essential in swarming motility of P. fluorescens SS101 and plays an important role in biofilm formation.

Glycolytic pathway and hydrogen yield studies of the extreme thermophile Caldicellulosiruptor saccharolyticus.

NMR analysis of (13)C-labelling patterns showed that the Embden-Meyerhof (EM) pathway is the main route for glycolysis in the extreme thermophile Caldicellulosiruptor saccharolyticus. Glucose fermentation via the EM pathway to acetate results in a theoretical yield of 4 mol of hydrogen and 2 mol of acetate per mole of glucose. Previously, approximately 70% of the theoretical maximum hydrogen yield has been reached in batch fermentations. In this study, hydrogen and acetate yields have been determined at different dilution rates during continuous cultivation. The yields were dependent on the growth rate. The highest hydrogen yields of 82 to 90% of theoretical maximum (3.3 to 3.6 mol H(2) per mol glucose) were obtained at low growth rates when a relatively larger part of the consumed glucose is used for maintenance. The hydrogen productivity showed the opposite effect. Both the specific and the volumetric hydrogen production rates were highest at the higher growth rates, reaching values of respectively 30 mmol g(-1) h(-1) and 20 mmol l(-1) h(-1). An industrial process for biohydrogen production will require a bioreactor design, which enables an optimal mix of high productivity and high yield.

Baerveldt glaucoma implant in paediatric patients.

AIM: To evaluate the Baerveldt glaucoma implant (BGI) in paediatric glaucoma treatment. METHODS: In a retrospective non-comparative case series 55 eyes of 40 consecutive paediatric patients (< or =16 years) with primary or secondary glaucoma underwent Baerveldt (350 mm2) implantation. Surgical outcome was evaluated by Kaplan-Meier table analysis. RESULTS: The overall success rate was 80% at last follow up, with a mean follow up of 32 (range 2-78) months. Cumulative success was 94% at 12 months and 24 months, 85% at 36 months, 78% at 48 months, and 44% at 60 months. 11 eyes (20%) failed postoperatively because of an IOP >21 mm Hg (eight eyes), persistent hypotony (two eyes), and choroidal haemorrhage following cataract surgery (one eye). The most frequent complication needing surgery was tube related (20%). A new observation was mild to moderate dyscoria in 22% of the eyes, all buphthalmic, caused by entrapment of a tuft of peripheral iris in the tube track. CONCLUSIONS: The BGI is effective and safe in the management of primary and secondary glaucoma. When angle surgery has proved to be unsuccessful or inappropriate in paediatric patients, a BGI is a good treatment option. One must be prepared to deal with the tube related problems.

Surgical revision of filtration blebs: a follow-up study.

PURPOSE: To assess the clinical outcome of one technique for surgical revision of filtration blebs in terms of bleb function and intraocular pressure control. METHODS: Retrospective analysis of 36 consecutive cases of leaking, overfiltrating, or oversized blebs treated with bleb excision and conjunctiva and Tenon advancement in a glaucoma referral center between January 1991 and December 1999. Surgical success was defined as a final intraocular pressure between 6 and 22 mm Hg with or without topical antiglaucoma medication, resolution of the bleb leak, hypotony maculopathy and symptoms, and no need for repeat glaucoma surgery. RESULTS: With a minimum of 12 months and an average of 29.5 months of follow-up, the overall success rate was 86.1%, with 51.6% of patients not requiring medication. In the success group, mean (SD) intraocular pressure was 23.7 (5.9) mm Hg before the original trabeculectomy, 4.3 (3.7) mm Hg prior to revision surgery, and 13.5 (SD 3.8) mm Hg at the last follow-up visit after the revision surgery. Mean number of antiglaucoma medications was 2.1 (range, 1-4) before the original trabeculectomy, none before the revision surgery, and 0.8 (range, 0-3) at the last follow-up visit. CONCLUSIONS: The surgical revision technique offers a definitive solution for most of these bleb complications and a satisfactory intraocular pressure control in the majority of patients.

Regiospecific effect of 1-octanol on cis-trans isomerization of unsaturated fatty acids in the solvent-tolerant strain Pseudomonas putida S12.

The solvent-tolerant bacterium Pseudomonas putida S12, which adapts its membrane lipids to the presence of toxic solvents by a cis to trans isomerization of unsaturated fatty acids, was used to study possible in vivo regiospecificity of the isomerase. Cells were supplemented with linoleic acid (C18:2delta9-cis,delta12-cis), a fatty acid that cannot be synthesized by this bacterium, but which was incorporated into membrane lipids up to an amount of 15% of total fatty acids. After addition of 1-octanol, which was used as an activator of the cis-trans isomerase, the linoleic acid was converted into the delta9-trans,delta12-cis isomer, while the delta9-cis,delta12-trans and delta9-trans,epsilon12-trans isomers were not synthesized. Thus, for the first time, regiospecific in vivo formation of novel, mixed cis/trans isomers of dienoic fatty acid chains was observed. The maximal conversion (27-36% of the chains) was obtained at 0.03-0.04% (v/v) octanol, after 2 h. The observed regiospecificity of the enzyme, which is located in the periplasmic space, could be due to penetration of the enzyme to a specific depth in the membrane as well as to specific molecular recognition of the substrate molecules.

Structural characterisation and enzymic modification of the exopolysaccharide produced by Lactococcus lactis subsp. cremoris B891.

Lactococcus lactis subsp. cremoris B891 grown on whey permeate produced an exopolysaccharide containing D-Gal and D-Glc in a molar ratio of 2:3. The polysaccharide was partially O-acetylated. By means of HF solvolysis, O-deacetylation, enzymic modification, sugar linkage analysis and ID/2D NMR studies the exopolysaccharide was shown to be composed of repeating units with the following structure: [structure: see text].

Retinal vasculitis occurring with common variable immunodeficiency syndrome.

PURPOSE: To report severe retinal vasculitis causing decreased vision in three patients with the common variable immunodeficiency syndrome. METHOD: Case report. Three patients with common variable immunodeficiency syndrome developed decreased vision secondary to retinal vasculitis. Fluorescein angiography was performed in all three patients. Peribulbar injections were given in one patient, and two patients were treated with oral steroids and cyclosporin. RESULTS: All three patients were young and had classic common variable immunodeficiency syndrome. Bilateral retinal vasculitis and diffuse retinal edema were present in all three patients, and two patients had retinal neovascularization in the absence of ischemia. No evidence of intraocular infection was present, and none was detected systematically. Visual acuity decreased in five of the six eyes and was responsive to treatment in only one patient (both eyes). CONCLUSION: Retinal vasculitis may be another autoimmune manifestation of common variable immunodeficiency syndrome.

Trypan blue capsule staining to visualize the capsulorhexis in cataract surgery.

A capsulorhexis may be difficult to perform in the absence of a red fundus reflex. Using 0.1 mL of trypan blue 0.1% to stain the anterior capsule in 30 patients with a mature cataract enabled us to visualize the capsulorhexis during phacoemulsification. No adverse reactions were observed up to 12 months after surgery. Trypan blue staining of the anterior capsule appears to be a safe technique to facilitate the performance of a capsulorhexis in the absence of a red fundus reflex.

[Staining the lens capsule with trypan blue for visualizing capsulorhexis in surgery of mature cataracts]. / Färbung der Linsenkapsel mit Trypanblau zur Visualisierung der Kapsulorhexis bei Maturkataraktchirurgie.

BACKGROUND: A capsulorhexis may be difficult to perform in the absence of a red fundus reflex. PATIENTS AND METHODS: After application of 0.3 mL trypan blue 0.1%, a quick and homogeneous staining of the anterior lens capsule was obtained in 100 patients with a mature cataract, to visualize the capsulorhexis during a phacoemulsification procedure. RESULTS: No adverse reactions related to the dye were observed up to 18 months after surgery. CONCLUSION: Trypan blue staining of the anterior lens capsule may therefore be a safe technique to facilitate the performance of a capsulorhexis in the absence of a red fundus reflex.

Rubeosis of the iris in proliferative vitreoretinopathy.

PURPOSE: The authors report the findings and clinical course of rubeosis in patients with essentially reattached retinas after vitrectomy and silicone oil for proliferative vitreoretinopathy (PVR). METHODS: From 1989 on, the authors prospectively noted all patients with rubeosis and with attached retina posterior to the buckle after vitrectomy and silicone oil for PVR as a complication of rhegmatogenous retinal detachment. RESULTS: Thirty-eight patients (38 eyes) were studied. Mean follow-up after the appearance of rubeosis was 27 months (range, 6-66 months) in all patients, peripheral residual retinal detachment coexisted with rubeosis. Hypotony occurred in six patients. Cyclocryocoagulation for neovascular glaucoma had been performed in four patients. The peripheral detached retina was removed in 16 patients, resulting in total disappearance of rubeosis in 7 patients and regression in 4 more patients. In patients with visible, nonradially oriented iris vessels, the authors found vessels in the anterior chamber angle crossing the trabecular meshwork. The frequently present anterior synechiae in association with vessels never totalled more than three clock hours (except in the four patients who underwent cyclocryocoagulation). CONCLUSIONS: Detached retina peripheral to dense photocoagulation scars was present in all of these patients. Removal of this peripheral detached retina was statistically significantly associated with disappearance of rubeosis, which suggests that the peripheral detachment was a causative factor. Extensive anterior synechiae are not formed frequently in this condition. This may explain the infrequent (11%) occurrence of neovascular glaucoma. However, hypotony is more frequent.

Molecular basis of glycoalkaloid induced membrane disruption.

In this study the interaction between the glycoalkaloids alpha-chaconine, alpha-solanine and alpha-tomatine and sterols in model membranes was analysed systematically using techniques like membrane leakage, binding experiments, detergent extraction, electron microscopy, NMR and molecular modelling. The most important properties for sterols to interact with glycoalkaloids turned out to be a planer ring structure and a 3 beta-OH group, whereas for alpha-chaconine the 5-6 double bond and the 10-methyl group were also of importance. The importance of sugar-sugar interactions was illustrated by the high synergistic effect between alpha-chaconine and alpha-solanine, the leakage enhancing effect of glycolipids, and the almost complete loss of activity after deleting one or more mono-saccharides from the glycoalkaloids. The formed complexes which were resistant against detergent extraction existed of glycoalkaloid/sterol in a 1:1 ratio and formed tubular structures (alpha-chaconine) with an inner monolayer of phospholipids, whereas with alpha-tomatine also spherical structures were formed. Based on the results a molecular model for glycoalkaloid induced membrane disruption is presented.

Formation of novel poly(hydroxyalkanoates) from long-chain fatty acids.

Poly(hydroxyalkanoates) (PHAs) were isolated from Pseudomonas aeruginosa 44T1 cultivated on euphorbia oil and castor oil. With the aid of 2-D proton NMR spectra and proton-detected multiple bond coherence NMR spectra the structures of the PHAs were determined. In addition to the usual PHA constituents (C6-C14 3-hydroxy fatty acids), PHAs formed from euphorbia oil contained delta 8,9-epoxy-3-hydroxy-5c-tetradecenoate, and probably delta 6,7-epoxy-3-hydroxydodecanoate and delta 4,5-epoxy-3-hydroxydecanoate. These novel constituents account for approximately 15% of the total amount of monomers and are clearly generated via beta-oxidation of vernolic acid (delta 12,13-epoxy-9c-octadecenoic acid), the main component of euphorbia oil. In PHAs formed from castor oil, 7% of the monomers found were derived from ricinoleic acid (12-hydroxy-9c-octadecenoic acid). The presence of 3,8-dihydroxy-5c-tetradecenoate was clearly demonstrated. Furthermore, NMR analysis strongly suggested the presence of 3,6-dihydroxydodecanoate, 6-hydroxy-3c-dodecenoate, and 4-hydroxydecanoate.

13C nuclear magnetic resonance studies of Pseudomonas putida fatty acid metabolic routes involved in poly(3-hydroxyalkanoate) synthesis.

The formation of poly(3-hydroxyalkanoates) (PHAs) in Pseudomonas putida KT2442 from various carbon sources was studied by 13C nuclear magnetic resonance spectroscopy, gas chromatography, and gas chromatography-mass spectroscopy. By using [1-13C]decanoate, the relation between beta-oxidation and PHA formation was confirmed. The labeling pattern in PHAs synthesized from [1-13C]acetate corresponded to the formation of PHAs via de novo fatty acid biosynthesis. Studies with specific inhibitors of the fatty acid metabolic pathways demonstrated that beta-oxidation and de novo fatty acid biosynthesis function independently in PHA formation. Analysis of PHAs derived from [1-13C]hexanoate showed that both fatty acid metabolic routes can function simultaneously in the synthesis of PHA. Furthermore, evidence is presented that during growth on medium-chain-length fatty acids, PHA precursors can be generated by elongation of these fatty acids with an acetyl coenzyme A molecule, presumably by a reverse action of 3-ketothiolase.

Heteronuclear NMR analysis of unsaturated fatty acids in poly(3-hydroxyalkanoates). Study of beta-oxidation in Pseudomonas putida.

Poly(3-hydroxyalkanoates) (PHAs) were isolated from Pseudomonas putida KT2442 cultivated on petroselenic acid, oleic acid, and linoleic acid to study beta-oxidation of unsaturated fatty acids. Both saturated and unsaturated medium chain length 3-hydroxy fatty acids were found to be constituents of these polymers. With the aid of proton-detected multiple quantum coherence and proton-detected multiple bond coherence NMR spectra the structures of the unsaturated monomers were identified as 3-hydroxy-5-cis-tetradecanoate for PHA produced on oleic acid, and 3-hydroxy-6-cis-dodecanoate and 3-hydroxy-5-cis-8-cis-tetradecadienoate for PHA produced on linoleic acid. The identified structures, which are derived from fatty acid degradation intermediates, indicate a degradation of oleic acid via the enoyl-CoA isomerase-dependent route and a degradation of linoleic acid via the dienoyl-CoA reductase-dependent route.

Application of 2D and 3D NMR experiments to the conformational study of a diantennary oligosaccharide.

By the application of homonuclear 3D NOE-HOHAHA and heteronuclear 3D HMQC-NOE experiments in studies of complex oligosaccharides, NOEs can be investigated which are hidden in conventional 2D NOE spectra. In the 3D NOE-HOHAHA spectrum omega 3 cross sections were considered to be the most suitable for assignment of NOEs. Alternatively, these cross sections could be measured separately in selective 2D HOHAHA-NOE spectroscopy. The advantages and limitations of the 2D alternative are compared with those of the 3D NOE-HOHAHA approach. In 3D HMQC-NOE spectroscopy the larger chemical shift displacement of the carbon spectrum with respect to the proton spectrum can be used to unmask NOEs hidden in the bulk region. If the extra proton dimension is not needed, 2D HMQC-NOE is a good alternative. The suitability of 2D and 3D NOE-HOHAHA and HMQC-NOE experiments for the estimation of proton-proton distances is demonstrated by comparing the results of these experiments on a diantennary asparagine-linked oligosaccharide with those of a conventional 2D NOE experiment. NOEs identified in the 2D and 3D NOE-HOHAHA as well as HMQC-NOE experiments, so far not identified or not quantified in 2D NOE experiments, are discussed in relation to each glycosidic linkage. The flexibility of the Man alpha (1-3)Man linkage is demonstrated, confirming the existence of an ensemble of conformations for this linkage.

Intraocular light scattering in age-related cataracts.

Intraocular light scattering was studied in 34 controls and 65 patients with cortical, nuclear, or posterior subcapsular cataracts by measuring forward scatter and backscatter. Forward scatter was measured by the psychophysical direct compensation method. Backscatter was determined with the Lens Opacity Meter of Interzeag. Contrast sensitivity loss caused by forward scatter was assessed with a glare tester (Vistech MCT 8000). Mean forward scatter was in the upper range for subcapsular cataracts compared to nuclear and cortical cataracts. Experimental results of the glare test (the contrast loss) deviated systematically from expected results based on measured forward scatter. Mean backscatter was largest for nuclear, intermediate for posterior subcapsular, and almost zero for cortical cataracts. Thus, each cataract has a characteristic mean ratio between forward scatter and backscatter. However, this ratio varied considerably among individuals, especially for cortical and posterior subcapsular cataracts. As a rule, forward scatter cannot be derived from backscatter (or the slit-lamp image).