P-362 The association between pregnancy-test day serum progesterone in IVF pregnancies and obstetrical complications

Study question

Is there an association between pregnancy-test day serum progesterone level in IVF pregnancies and late gestational complications?

Summary answer

Low serum progesterone on pregnancy diagnosis day is independently associated with a higher prevalence of preeclampsia.

What is known already

Low first trimester arbitrary serum progesterone is associated with early pregnancy complications such as ectopic pregnancies and miscarriages. IVF pregnancies are associated with higher prevalence of obstetrical complications such as preterm birth, preeclampsia and small for gestational age. Different patient and treatment parameters such as age, diagnosis, peak blood Estradiol level, endometrial thickness, fresh or frozen embryo transfer are associated with obstetrical complications. Progesterone is a potent immunomodulator that can affect the inflammatory pathway and trophoblast invasion. Little is known about the association between early pregnancy progesterone level and obstetrical complications, with conflicting results.

Study design, size, duration

A cohort study reviewing fertility and delivery files of all singleton live births from successfully treated infertile patients, who underwent ovarian stimulation, IVF and fresh embryo transfer in a tertiary medical center between 2008 and 2018.

Participants/materials, setting, methods

Serum progesterone concentration was measured with the first serum hCG on 4 + 0 gestational week (14 days after oocyte retrieval) under luteal support with vaginal progesterone. Pregnancy-test day serum progesterone was categorized in quartiles. The prevalence of obstetrical complications including gestational diabetes mellitus, preterm birth, preeclamsia, small for gestational age, post-partum hemorrhage and neonatal ICU hospitalization was compared between the four groups. Confounders were adjusted for by multivariate analysis.

Main results and the role of chance

719 singleton live births were included. The four serum progesterone quartiles were: Q1:3-44 nmol/L(n = 180); Q2:45-107 nmol/L(n = 180); Q3:108-223 nmol/L(n = 178); Q4:225-808nmol/L(n = 181). Patients with lower progesterone levels (Q1) had significantly more IVF treatments, lower peak estradiol level, fewer mature follicles and frozen embryos. The incidence of preterm labor, gestational diabetes mellitus, small-for-gestational-age, post-partum hemorrhage, placental abruption or neonatal ICU administration did not differ between the groups. Patients with lower serum progesterone had higher incidence of preeclampsia (9.44% in Q1, 2.78% in Q2, 2.81% in Q3 and 3.31% in Q4, P = 0.0046). On multivariate analysis, controlling for age, gravidity, treatment number, number of oocytes, peak follicular estradiol and progesterone, Q1 progesterone level was independently associated with an increased risk of preeclampsia (estimated OR = 3.27 95% CI 1.455-7.299).

Limitations, reasons for caution

Retrospective design, vaginal progesterone luteal support administration.

Wider implications of the findings

Low serum progesterone on pregnancy diagnosis day in gestations resulting from fresh ET is associated with a significantly higher prevalence of preeclampsia, possibly because of aberrant placentation and vascular development. This association is important for the obstetrical management, preeclampsia risk assessment, and administration of preventive therapy.

Trial registration number

not applicable

P-770 Is there an association between blood hCG elevation rate in very early IVF pregnancy and adverse pregnancy outcomes?

Study question

Is a slow elevation rate between the first and second hCG values following a successful fresh IVF cycle associated with long-term pregnancy outcomes?

Summary answer

A slow rate of hCG elevation in early IVF pregnancies is associated with an increased risk for low birth weight neonates.

What is known already

IVF pregnancies are associated with higher prevalence of late obstetrical complications such as preterm birth, preeclampsia and small for gestational age. Different baseline characteristics and treatment parameters are associated with obstetrical complications. Abnormal, mostly slow, hCG elevation patterns have been strongly associated with short-term adverse pregnancy outcomes such as non-viability, miscarriage, early fetal demise and ectopic pregnancies. However, the long-term impact of slow hCG elevation rate on pregnancies that do continue to term is unknown.

Study design, size, duration

Single center cohort study between 2008-2019 including 703 fresh cycles resulting in live singleton birth. Full obstetrical data for these pregnancies was available.

Participants/materials, setting, methods

The first blood hCG measurement was performed 14±1.4 days after ovum pick-up (OPU), and the second one 48-72h later. The slope between the two measurements was calculated and adjusted per day. Slow hCG elevation was defined as a slope value below the 10th percentile. Maternal and short-term neonatal outcomes were compared between cycles with a slow elevation (n = 71) and a “normal” elevation (n = 632) in hCG values. Multivariate analysis was used to control for potential confounders.

Main results and the role of chance

There were no differences between the slow and normal hCG elevation groups in maternal age, numbers of retrieved oocytes, ICSI rates, number of transferred and usable embryos, and gestational age at delivery. Neonates from cycles with a slow hCG elevation weighed significantly less (2876±619 gr vs. 3083±553 gr, p < 0.005) and were at a higher risk (21% vs. 12%, OR = 1.96, 95% CI 1.06-3.64) of having low birth weight (LBW) (below 2500 grams). Women with slow hCG elevation rate had more hypertension-preeclampsia related complications (11% vs. 6%, p < 0.05), although barely reaching statistical significance in the multivariate analysis (OR = 1.76, 95% CI 1.0-3.6).

Limitations, reasons for caution

Retrospective design, single center, applicability to fresh cycles only.

Wider implications of the findings

Very early (5th week) initial blood hCG elevation slope, measured only in IVF gestations, might be a novel marker for identifying patients at risk for hypertensive complications during pregnancy and low birth-weight neonates. Tighter prenatal care for these patients could potentially reduce pregnancy complications and improve long-term outcome.

Trial registration number

not applicable

The Mask Game with Multiple Populations

Masks save lives. Therefore, while the culture of wearing masks is promoted, it is critical to understand the various aspects of how that culture is adopted. The main contribution of this paper is in the modeling of the mask game. Wearing a mask provides partial protection against epidemics at some cost of comfort. Players can be differentiated according to both their risk state as well as their health state (susceptible, infected and removed). We formulate the problem as a Bayesian game in which players know their own risk state and ignore their own health state and the health and risk states of their counterparts. Using ideas from evolutionary games, we reduce the problem to a one-shot equivalent game and describe the structure of the symmetric equilibria. We prove that the policies adopted by the players at such equilibria admit a threshold structure. More specifically, players wear masks only if their risk state is equal to or bigger than a given threshold.

Preface to Special Issue on Dynamic Games for Modeling and Control of Epidemics

This preface introduces the special issue on Dynamic Games for Modeling and Control of Epidemics. It showcases 12 papers with timely contributions to dynamic games and their applications to the modeling, analysis, and control of epidemics. The papers in this collection connect dynamic games and epidemic models to address the recent challenges related to screening, containment, and mitigation strategies for epidemics. This collection covers broad application areas in networks, human behaviors, and epidemiology as well as a diverse range of dynamic game methods, including evolutionary games, differential games, and mean-field games.

DINVESTIGATION OF CONTACT HEATING OF FRUIT AND VEGETABLES WITH SATURATED WATER STEAM

The purpose of this research was to study the modes of  heating different types of plant raw materials in model technological environments that imitate the blanching of raw materials under factory conditions. The research aimed at expanding the range of canned products made from fruit and vegetables. To this end, new methods were searched for, in addition to the existing ones, allowing heating various plant raw materials and increasing the energy efficiency of canned fruit and vegetables production. Saturated water steam was selected as the treatment medium. The experimental studies included determining the volume-average  temperature of the fruit layer in the container. A pulse method of supplying the heating media has also been investigated. It allows using the inertial properties of raw materials and significantly reducing the expenditure of the heating media.  The objects selected for study were various species of pomes and drupes, in particular, apples, plums, cherries, sweet cherries, as well as a vegetable crop of the gourd family, or Cucurbitaceae. The following characteristics have been studied: the dynamics of heating individual fruit and vegetables in the saturated water steam environment at atmospheric pressure; the dependence of the heating and cooling rates of individual fruit and vegetables on the geometric index; the dependence of the heating rate of individual fruit and vegetables on the value of the characteristic dimension; the dependences of changes in the volume-average temperature of the fruit layer on the duration of treatment with saturated water steam. It has been established that the volume-average temperature in the centre of a fruit is also influenced by the shape of the fruit itself. To characterise the anomalous shapes of plant raw materials, the geometric index G has been calculated. This index characterises the elliptical shape of a fruit, and allows determining parameters in two mutually perpendicular planes. Also, to compare fruit of the elliptical and the spherical shapes, a special concept of characteristic dimension was used, which is applicable to fruit of different shapes. The experimental data on the change in the dependences of the heating and cooling rates of individual elliptical fruit have been analysed. The analysis has shown that the size of a fruit significantly affects the volume-average temperature in the fruit layer. It has been suggested to use pulsed heating of the fruit layer with saturated  water steam, which will appreciably increase the energy efficiency of production due to a significant reduction in heating media consumption

On the True Number of COVID-19 Infections: Effect of Sensitivity, Specificity and Number of Tests on Prevalence Ratio Estimation

In this paper, a formula for estimating the prevalence ratio of a disease in a population that is tested with imperfect tests is given. The formula is in terms of the fraction of positive test results and test parameters, i.e., probability of true positives (sensitivity) and the probability of true negatives (specificity). The motivation of this work arises in the context of the COVID-19 pandemic in which estimating the number of infected individuals depends on the sensitivity and specificity of the tests. In this context, it is shown that approximating the prevalence ratio by the ratio between the number of positive tests and the total number of tested individuals leads to dramatically high estimation errors, and thus, unadapted public health policies. The relevance of estimating the prevalence ratio using the formula presented in this work is that precision increases with the number of tests. Two conclusions are drawn from this work. First, in order to ensure that a reliable estimation is achieved with a finite number of tests, testing campaigns must be implemented with tests for which the sum of the sensitivity and the specificity is sufficiently different than one. Second, the key parameter for reducing the estimation error is the number of tests. For a large number of tests, as long as the sum of the sensitivity and specificity is different than one, the exact values of these parameters have very little impact on the estimation error.

Topological Defects in Anisotropic Driven Open Systems

We study the dynamics and unbinding transition of vortices in the compact anisotropic Kardar-Parisi-Zhang equation. The combination of nonequilibrium conditions and strong spatial anisotropy drastically affects the structure of vortices and amplifies their mutual binding forces, thus stabilizing the ordered phase. We find novel universal critical behavior in the vortex-unbinding crossover in finite-size systems. These results are relevant for a wide variety of physical systems, ranging from strongly coupled light-matter quantum systems to dissipative time crystals.

Open-loop routeing to M parallel servers with no buffers

In this paper we study the assignment of packets to M parallel heterogeneous servers with no buffers. The controller does not have knowledge on the state of the servers and bases all decisions on the number of time slots ago that packets have been sent to the different servers. The objective of the controller is to minimize the expected average cost. We consider a general stationary arrival process, with no independence assumptions. We show that the problem can be transformed into a Markov Decision Process (MDP). We further show under quite general conditions on cost functions that only a finite number of states have to be considered in this MDP, which then implies the optimality of periodic policies. For the case of two servers we obtain a more detailed structure of the cost and optimal policies. In particular we show that the average cost function is multimodular, and we obtain expressions for the cost for MMPP and MAP processes. Finally we present an application to optimal robot scheduling for Web search engines.

Perturbation analysis for denumerable Markov chains with application to queueing models

We study the parametric perturbation of Markov chains with denumerable state spaces. We consider both regular and singular perturbations. By the latter we mean that transition probabilities of a Markov chain, with several ergodic classes, are perturbed such that (rare) transitions among the different ergodic classes of the unperturbed chain are allowed. Singularly perturbed Markov chains have been studied in the literature under more restrictive assumptions such as strong recurrence ergodicity or Doeblin conditions. We relax these conditions so that our results can be applied to queueing models (where the conditions mentioned above typically fail to hold). Assuming ν-geometric ergodicity, we are able to explicitly express the steady-state distribution of the perturbed Markov chain as a Taylor series in the perturbation parameter. We apply our results to quasi-birth-and-death processes and queueing models.

Queueing in space

We consider a problem in which a single server must serve a stream of customers whose arrivals are distributed over a finite-size convex space. Under the assumption that the server has full information on the customer location, obvious service policies are the FCFS and the greedy (serve-the-closest-customer) approaches. These algorithms are, however, either inefficient (FCFS) or ‘unfair' (greedy).

We propose and study two alternative algorithms, the gated-greedy policy and the gated-scan policy, which are more ‘fair' than the pure greedy method. We show that the stability conditions of the gated-greedy are p < 1 (where p is the expected rate at which work arrives at the system), implying that the method is at least as efficient (in terms of system stability) as any other discipline, in particular the greedy one. For the gated-scan policy we show that for any p < 1 one can design a stable gated-scan policy; however, for any fixed gated-scan policy there exists p < 1 for which the policy is unstable. We evaluate the performance of the gated-scan policy, and present bounds for the performance of the gated-greedy policy.

These results are derived for systems in which the arrivals occur on a two-dimensional space (a square) but they are not limited to this configuration; rather they hold for more complex N-dimensional spaces, in particular for serving customers in (three-dimensional) convex space and serving customers on a line.

Anterior parasternal approach for creation of a pericardial window

INTRODUCTION

The optimal method for creation of a pericardial window (PW) is still controversial and it remains a surgical challenge, mainly in obese patients. The aim of this study was to evaluate the efficacy and safety of a novel approach that has not been described previously, for creation of a PW in patients with symptomatic, chronic, large pericardial effusion.

METHODS

We retrospectively analysed the records of 30 patients (14 men, 16 women) who underwent a PW procedure between 2001 and 2011. The mean age was 63 years (standard deviation [SD]: 17 years, median: 60 years, range: 27-90 years) and the mean body mass index was 34 kg/m(2) (SD: 2 kg/m(2)). The operation was performed through a curvilinear parasternal approach, 6-8 cm in length, followed by a mini-thoracotomy between ribs 4 and 5. Discharged patients were followed up clinically.

RESULTS

The mean operative time was 73 minutes (SD: 21 minutes) and a median of 658 ml (range: 300-1,500 ml) of fluid was evacuated. The main aetiologies were idiopathic in 17 patients (57%) and malignant in 9 (30%). Seven patients (23%) died in hospital owing to underlying malignancy. Postoperative complications included mild renal failure (20%), respiratory failure (20%), pneumonia (13%), atrial fibrillation (10%) and atelectasis (6%). There were no wound infections. The median length of stay following the procedure was 8 days. In a median follow-up period of 3.8 years, 16 patients with non-malignant effusion were free of recurrence of pericardial effusion.

CONCLUSIONS

The anterior parasternal approach for creation of a PW is simple, safe and efficacious, and results in long-term symptomatic improvement, specifically in patients with non-malignant effusions. This approach may be more appealing in obese patients.

Stationary Anonymous Sequential Games with Undiscounted Rewards

Stationary anonymous sequential games with undiscounted rewards are a special class of games that combine features from both population games (infinitely many players) with stochastic games. We extend the theory for these games to the cases of total expected reward as well as to the expected average reward. We show that in the anonymous sequential game equilibria correspond to the limits of those of related finite population games as the number of players grows to infinity. We provide examples to illustrate our results.

Dynamical critical phenomena in driven-dissipative systems

We explore the nature of the Bose condensation transition in driven open quantum systems, such as exciton-polariton condensates. Using a functional renormalization group approach formulated in the Keldysh framework, we characterize the dynamical critical behavior that governs decoherence and an effective thermalization of the low frequency dynamics. We identify a critical exponent special to the driven system, showing that it defines a new dynamical universality class. Hence critical points in driven systems lie beyond the standard classification of equilibrium dynamical phase transitions. We show how the new critical exponent can be probed in experiments with driven cold atomic systems and exciton-polariton condensates.

Quasiparticle dynamics in a bose insulator probed by interband bragg spectroscopy

We investigate experimentally and theoretically the dynamical properties of a Mott insulator in decoupled one-dimensional chains. Using a theoretical analysis of the Bragg excitation scheme, we show that the spectrum of interband transitions holds information on the single-particle Green's function of the insulator. In particular, the existence of particle-hole coherence due to quantum fluctuations in the Mott state is clearly seen in the Bragg spectra and quantified. Finally, we propose a scheme to directly measure the full, momentum-resolved spectral function as obtained in the angle-resolved photoemission spectroscopy of solids.

Topological insulators in magnetic fields: quantum Hall effect and edge channels with a nonquantized θ term

We investigate how a magnetic field induces one-dimensional edge channels when the two-dimensional surface states of three-dimensional topological insulators become gapped. The Hall effect, measured by contacting those channels, remains quantized even in situations where the θ term in the bulk and the associated surface Hall conductivities, σ(xy)(S), are not quantized due to the breaking of time-reversal symmetry. The quantization arises as the θ term changes by ±2πn along a loop around n edge channels. Model calculations show how an interplay of orbital and Zeeman effects leads to quantum Hall transitions, where channels get redistributed along the edges of the crystal. The network of edges opens new possibilities to investigate the coupling of edge channels.

Noise correlations in one-dimensional systems of ultracold fermions

Time of flight images reflect the momentum distribution of the atoms in the trap, but the spatial noise in the image holds information on more subtle correlations. Using bosonization, we study such correlations in generic 1D systems of ultracold fermions. We show how pairing as well as spin and charge density wave correlations may be identified and extracted from time of flight images. These incipient orders manifest themselves as power-law singularities in the noise correlations, that depend on the Luttinger parameters, which suggests a general experimental technique to obtain them.

Amplitude mode in the quantum phase model

We derive the collective low-energy excitations of the quantum phase model of interacting lattice bosons within the superfluid state using a dynamical variational approach. We recover the well-known sound (or Goldstone) mode and derive a gapped (Higgs-type) mode that was overlooked in previous studies of the quantum phase model. This mode is relevant to ultracold atoms in a strong optical lattice potential. We predict the signature of the gapped mode in lattice modulation experiments and show how it evolves with increasing interaction strength.

Intrinsic dephasing in one-dimensional ultracold atom interferometers

Quantum-phase fluctuations prevent true long-range phase order from forming in interacting 1D condensates, even at zero temperature. Nevertheless, by dynamically splitting the condensate into two parallel decoupled tubes the system can be prepared with a macroscopic relative phase, facilitating interferometric measurement. Here, we describe a dephasing mechanism whereby the quantum-phase fluctuations, which are so effective in equilibrium, act to destroy the macroscopic relative phase that was imposed as a nonequilibrium initial condition. We show that the phase coherence between the condensates decays exponentially with a dephasing time that depends on intrinsic parameters: the interaction strength, sound velocity, and density. Interestingly, significant temperature dependence appears only above a cross-over scale T*. In contrast to the usual phase diffusion, which is essentially an effect of confinement and leads to Gaussian decay, the exponential dephasing caused by fluctuations is a bulk effect that survives the thermodynamic limit.

Homolactate fermentation by metabolically engineered Escherichia coli strains

We report the homofermentative production of lactate in Escherichia coli strains containing mutations in the aceEF, pfl, poxB, and pps genes, which encode the pyruvate dehydrogenase complex, pyruvate formate lyase, pyruvate oxidase, and phosphoenolpyruvate synthase, respectively. The process uses a defined medium and two distinct fermentation phases: aerobic growth to an optical density of about 30, followed by nongrowth, anaerobic production. Strain YYC202 (aceEF pfl poxB pps) generated 90 g/liter lactate in 16 h during the anaerobic phase (with a yield of 0.95 g/g and a productivity of 5.6 g/liter . h). Ca(OH)(2) was found to be superior to NaOH for pH control, and interestingly, significant succinate also accumulated (over 7 g/liter) despite the use of N(2) for maintaining anaerobic conditions. Strain ALS961 (YYC202 ppc) prevented succinate accumulation, but growth was very poor. Strain ALS974 (YYC202 frdABCD) reduced succinate formation by 70% to less than 3 g/liter. (13)C nuclear magnetic resonance analysis using uniformly labeled acetate demonstrated that succinate formation by ALS974 was biochemically derived from acetate in the medium. The absence of uniformly labeled succinate, however, demonstrated that glyoxylate did not reenter the tricarboxylic acid cycle via oxaloacetate. By minimizing the residual acetate at the time that the production phase commenced, the process with ALS974 achieved 138 g/liter lactate (1.55 M, 97% of the carbon products), with a yield of 0.99 g/g and a productivity of 6.3 g/liter . h during the anaerobic phase.

Increased recombinant protein production inEscherichia coli strains with overexpressed water-forming NADH oxidase and a deleted ArcA regulatory protein

Glycolytic flux is increased and acetate production is reduced in Escherichia coli by the expression of heterologous NADH oxidase (NOX) from Streptococcus pneumoniae coupled with the deletion of the arcA gene, which encodes the ArcA regulatory protein. In this study, we examined the overproduction of a model recombinant protein in strains of E. coli expressing NOX with or without an arcA mutation. The presence of NOX or the absence of ArcA reduced acetate by about 50% and increased beta-galactosidase production by 10-20%. The presence of NOX in the arcA strain eliminated acetate production entirely in batch fermentations and resulted in a 120% increase in beta-galactosidase production.

Overflow metabolism in Escherichia coli during steady-state growth: transcriptional regulation and effect of the redox ratio

Overflow metabolism in the form of aerobic acetate excretion by Escherichia coli is an important physiological characteristic of this common industrial microorganism. Although acetate formation occurs under conditions of high glucose consumption, the genetic mechanisms that trigger this phenomenon are not clearly understood. We report on the role of the NADH/NAD ratio (redox ratio) in overflow metabolism. We modulated the redox ratio in E. coli through the expression of Streptococcus pneumoniae (water-forming) NADH oxidase. Using steady-state chemostat cultures, we demonstrated a strong correlation between acetate formation and this redox ratio. We furthermore completed genome-wide transcription analyses of a control E. coli strain and an E. coli strain overexpressing NADH oxidase. The transcription results showed that in the control strain, several genes involved in the tricarboxylic acid (TCA) cycle and respiration were repressed as the glucose consumption rate increased. Moreover, the relative repression of these genes was alleviated by expression of NADH oxidase and the resulting reduced redox ratio. Analysis of a promoter binding site upstream of the genes which correlated with redox ratio revealed a degenerate sequence with strong homology with the binding site for ArcA. Deletion of arcA resulted in acetate reduction and increased the biomass yield due to the increased capacities of the TCA cycle and respiration. Acetate formation was completely eliminated by reducing the redox ratio through expression of NADH oxidase in the arcA mutant, even at a very high glucose consumption rate. The results provide a basis for studying new regulatory mechanisms prevalent at reduced NADH/NAD ratios, as well as for designing more efficient bioprocesses.

Superfluid-insulator transition in a moving system of interacting bosons

We analyze the stability of superfluid currents in a system of strongly interacting ultracold atoms in an optical lattice. We show that such a system undergoes a dynamic, irreversible phase transition at a critical phase gradient that depends on the interaction strength between atoms. At commensurate filling, the phase boundary continuously interpolates between the classical modulation instability of a weakly interacting condensate and the equilibrium quantum phase transition into a Mott insulator state at which the critical current vanishes. We argue that quantum fluctuations smear the transition boundary in low dimensional systems. Finally we discuss the implications to realistic experiments.

Physiological response of central metabolism inEscherichia coli to deletion of pyruvate oxidase and introduction of heterologous pyruvate carboxylase

We studied the physiological response of Escherichia coli central metabolism to the expression of heterologous pyruvate carboxylase (PYC) in the presence and absence of pyruvate oxidase (POX). These studies were complemented with expression analysis of central and intermediary metabolic genes and conventional in vitro enzyme assays to evaluate glucose metabolism at steady-state growth conditions (chemostats). The absence of POX activity reduced nongrowth-related energy metabolism (maintenance coefficient) and increased the maximum specific rate of oxygen consumption. The presence of PYC activity (i.e., with POX activity) increased the biomass yield coefficient and reduced the maximum specific oxygen consumption rate compared to the wildtype. The presence of PYC in a poxB mutant resulted in a 42% lower maintenance coefficient and a 42% greater biomass yield compared to the wildtype. Providing E. coli with PYC or removing POX increased the threshold specific growth rate at which acetate accumulation began, with an 80% reduction in acetate accumulation observed at a specific growth rate of 0.4 h-1 in the poxB-pyc+ strain. Gene expression analysis suggests utilization of energetically less favorable glucose metabolism via glucokinase and the Entner-Doudoroff pathway in the absence of functional POX, while the upregulation of the phosphotransferase glucose uptake system and several amino acid biosynthetic pathways occurs in the presence of PYC. The physiological and expression changes resulting from these genetic perturbations demonstrate the importance of the pyruvate node in respiration and its impact on acetate overflow during aerobic growth.

Helicobacter pylori with a truncated lipopolysaccharide O chain fails to induce gastritis in SCID mice injected with splenocytes from wild-type C57BL/6J mice

The goal of this study was to determine whether Helicobacter pylori lipopolysaccharide (LPS) O-chain polysaccharide contributes to gastritis in a mouse model. C57BL/6J or C57BL/6-Prkdc(scid) (severe combined immunodeficient [SCID]) mice were inoculated with H. pylori strain SS1 or SS1::0826kan, in which a beta-1,4-galactosyltransferase (HP0826), an LPS biosynthetic enzyme, had been disrupted. H. pylori strain SS1::0826kan expresses truncated LPS lacking O chain. Recipient SCID mice were given C57BL/6J splenocytes by intraperitoneal injection. Bacterial colonization, gastric lesions (gastritis, neutrophilic infiltration, and gastric epithelial metaplasia), cellular (delayed-type hypersensitivity) and humoral immune responses to H. pylori sonicate, and gastric gamma interferon (IFN-gamma) mRNA expression were quantified. Recipient SCID mice colonized by H. pylori strain SS1 developed extensive gastritis with loss of normal fundic gland morphology. In contrast, gastric mucosa of recipient SCID mice colonized by H. pylori strain SS1::0826kan was not statistically distinguishable from that of uninfected recipient mice. Delayed-type hypersensitivity and humoral immune responses were detected in infected mice inoculated with wild-type SS1, but not with SS1::0826kan. IFN-gamma transcription was lower in mice infected with SS1::0826kan than in mice infected with SS1. In this model of rapidly progressive gastritis due to H. pylori, the O chain contributed to the extent of gastritis and to the host immune response. These data support a role for H. pylori LPS O chain in direct induction of the host immune response leading to gastritis and gastric damage and are in contrast to protein antigens, such as urease and cag products which do not contribute to gastritis in mice.

Production of 5-aminolevulinic acid by an Escherichia coli aminolevulinate dehydratase mutant that overproduces Rhodobacter sphaeroides aminolevulinate synthase

Two Escherichia coli strains, a wild-type strain and a hemB mutant, which contained the hemA gene from Rhodobacter sphaeroides produced aminolevulinate at 4 g l(-1). The hemB mutant did not increase the accumulation of aminolevulinate, an observation attributed to its 50% lower aminolevulinate synthase activity in than the wild-type. Growth was limited for both strains probably due to the accumulation of 0.5 g aminoacetone l(-1).

Using protein-based motifs to stabilize peptides

While the use of synthetically derived novel inhibitor peptides as a source of new therapeutics for medicine remains incredibly promising, there is a major problem with implementing this technology, as many synthetic peptides have proven to be unstable and are degraded by peptidases in the host cell. In this study, we have investigated methods by which peptides can be stabilized using protein-based motifs in order to prevent the action of peptidases. Using an in vivo approach our laboratory developed to screen for synthetic peptides which can inhibit the growth of Escherichia coli, we found that protecting the amino or carboxyl terminus of the peptides via fusion to the very stable Rop protein, or the incorporation of two proline residues, increased the frequency at which potent inhibitor peptides could be isolated. Using an in vitro degradation assay in which extracts from several different cell types were tested, we demonstrated that peptides stabilized with multiple proline residues were more resistant to degradation than peptides stabilized by amidation or acetylation, two approaches that are routinely utilized to improve the stability of peptide drugs.

Aerobic production of alanine by Escherichia coli aceF ldhA mutants expressing the Bacillus sphaericus alaD gene

Alanine was produced from glucose in an Escherichia coli aceF ldhA double mutant strain that contained the pTrc99A- alaD plasmid expressing Bacillus sphaericus alanine dehydrogenase. The aceF gene encodes one of the proteins of the pyruvate dehydrogenase complex, and therefore this strain required acetate as an additional carbon source. The ldhA gene encodes fermentative lactate dehydrogenase, a competitor of alanine dehydrogenase for the substrate pyruvate. Fermentations included an oxygenated growth phase followed by an oxygen-limited alanine production phase. The lowest value for the mass transfer coefficient ( k(L)a) studied during the production phase yielded the greatest alanine. With feeding of glucose and NH(4)Cl, 32 g/l alanine accumulated in 27 h with a yield of 0.63 g alanine generated per gram glucose consumed.

Optimization of recombinant aminolevulinate synthase production in Escherichia coli using factorial design

The production of recombinant Rhodobacter sphaeroides aminolevulinate (ALA) synthase was optimized in two strains of Escherichia coli: the wild-type strain MG1655, and a ptsG mutant AFP111. The effects of initial succinate, glucose and isopropyl-beta-d-thiogalactopyranoside (IPTG) concentrations and the time of induction on enzyme activity were studied. One-way analysis was used to approximate the optimal ranges for these factors, followed by a full factorial design to quantify the effects of each factor and the interactions between the factors. Initial succinate, glucose, and IPTG concentration were observed to be the key factors affecting ALA synthase activity with the optimal levels determined to be above 6 g/l succinate, 0 g/l glucose, and 0.10 mM IPTG. ALA synthase activity was generally lower with AFP111 than with MG1655, and the effect of these three key factors was also lower with AFP111 than with MG1655. Based on the full factorial design results, a fermentation was completed that yielded 296 mU/mg protein with a final ALA concentration of 5.2 g/l (39 mM).

The effect of acetate pathway mutations on the production of pyruvate in Escherichia coli

We compared pyruvate accumulation in six strains of Escherichia coli and their corresponding ppc mutants. Each strain contained a mutation of a gene involved in the pathway to acetate synthesis. Strains with mutations in genes encoding the pyruvate dehydrogenase complex generally exhibited the greatest pyruvate accumulation of which CGSC6162 (an aceF mutant) and CGSC6162 Delta ppc were studied in greater detail in controlled fermenters. Both CGSC6162 and CGSC6162 Delta ppc accumulated greater than 35 g/l pyruvate in a medium supplemented with acetate. We observed pyruvate mass yields from glucose of 0.72 in CGSC6162, with volumetric productivities above 1.5 g l(-1) h(-1). For CGSC6162 Delta ppc, we observed pyruvate yields of 0.78 and volumetric productivities above 1.2 g l(-1) h(-1). CGSC6162 consumed all initially supplied acetate, while CGSC6162 Delta ppc first consumed and then generated acetate during the course of a 36 h fermentation. Acetate generation and pyruvate oxidase activity was pH- and temperature-dependent, with a pH of 7.0 and the lowest temperature studied (32 degrees C) favoring the greatest pyruvate generation. Lactate was an unexpected by-product even though measured lactate dehydrogenase (LDH) activity was very low.