Diffusion-Weighted Imaging of the Orbit: A Case Series and Systematic Review

PURPOSE

To describe the findings of diffusion-weighted imaging (DWI) for a series of orbital lesions and provide a systematic review of relevant literature.

METHODS

A retrospective review of 20 patients with orbital lesions who underwent MRI with DWI at two academic institutions between 2015 and 2020 was performed. Lesion diagnosis was histopathologically confirmed except a presumed cavernous hemangioma. Echoplanar diffusion-weighted images had been acquired using 2 or 3 b values (b=0 and 1000 or b=0, 500, and 1000) at 1.5T or 3T. Lesions with significant artifacts were excluded. DWI sequences were analyzed by neuro-radiologists blinded to the diagnosis. Mean ADC values of lesions were calculated from a single region of interest. An independent two-tailed t test was used to compare categories of lesions with p < 0.05 considered significant. A systematic review of the literature was performed.

RESULTS

Our study included 21 lesions. ADC values were significantly lower for malignant lesions (0.628 ± 0.125 × 10 -3 mm 2 /s) than inflammatory lesions (1.167 ± 0.381 × 10 -3 mm 2 /s) ( p < 0.001). ADC values were significantly lower for orbital lymphoma (mean 0.621 ± 0.147 × 10 -3 mm 2 /s) than idiopathic orbital inflammation (mean 1.188 ± 0.269 × 10 -3 mm 2 /s) with no overlap ( p < 0.001).

CONCLUSIONS

Orbital malignancies demonstrated lower ADC values, while inflammatory processes demonstrated higher ADC values, except IgG4-related disease. DWI and ADC values differentiated idiopathic orbital inflammation from orbital lymphoma. This study highlights the role of DWI in evaluating orbital pathology.

Short-term outcomes in patients with center-involving diabetic macular edema after a single dose of intravitreal bevacizumab

Background

A significant portion of diabetic macular edema (DME) is refractory to anti-vascular endothelial growth factor (anti-VEGF) agents. This study investigates morphological and functional outcomes to a single intravitreal bevacizumab (IVB) injection in patients with center-involving DME (ciDME) at 4–6 weeks and compares treatment responders and non-responders based on spectral domain optical coherence tomography (SD-OCT) features.

Methods

IRB approved observational, retrospective chart review of patients with ciDME, identified by ICD-10 code, who received IVB and underwent baseline and 4–6 weeks follow-up SD-OCT imaging between January 1, 2016 and January 19, 2021. Patients who had received previous treatment with anti-VEGF or intraocular steroids within 1 year were excluded. Variables included best-corrected visual acuity (BCVA), central subfield thickness (CST) and total macular volume (TMV). Eyes were classified as responders if CST reduction was greater than 10%. OCT scans were graded qualitatively by two masked graders using Imagivault software. Paired Student’s t-tests, Wilcoxon signed rank tests and Chi-Square tests were used for analysis.

Results

A total of 334 prospective subjects were identified, and after applying exclusion criteria 52 eyes from 46 patients (mean age 64.22 ± 8.12 years, 58.7% male) were included. Mean BCVA did not significantly change with treatment, 63.9 ETDRS letters (~ 20/50) at baseline and 65.9 ETDRS letters (~ 20/50) post-treatment (p = 0.07). Mean CST decreased from 466 ± 123 μm at baseline to 402 ± 86 μm post-treatment (p < 0.001). 22 (42.3%) of eyes were categorized as responders and 30 (57.7%) as non-responders. Average change in CST from baseline in responders was -164 μm (p < 0.001) and + 9 μm in non-responders (p = 0.47). Vitreomacular adhesion (VMA) was more prevalent in non-responders (28.7% vs. 4.8%, p = 0.03). In addition, cyst location in the inner nuclear layer (INL) was present more frequently in responders (95.5% vs. 73.3%, p = 0.037) as was subretinal fluid (45.5% vs. 13.3%, p = 0.01).

Conclusion

The short-term response to a single IVB was sub-optimal with structural but no functional improvements. Greater baseline CST, presence of INL cysts and subretinal fluid may represent factors indicative of a better treatment response.

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 &lt; 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 &lt; 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

Pandemic-related financial hardship and disparities in sugar-sweetened beverage consumption and purchasing among San Francisco Bay Area residents during COVID-19

Some reports suggest that the COVID-19 pandemic resulted in shifts to unhealthier diets. These unhealthier diets may include sugar-sweetened beverages (SSBs), which strongly contribute to diabetes and other chronic diseases. Using cross-sectional surveys in the San Francisco Bay Area, California, USA we sought to assess self-reported SSB consumption during the pandemic's shelter-in-place and self-reported changes in SSB purchasing from before to during the pandemic's shelter-in-place, stratifying by indices of pandemic-related financial hardship. Nearly 60% of our diverse sample (N = 943) reported that it was harder to pay for basics (like food and utilities) during shelter-in-place. Among those who found it harder to pay for basics and received financial assistance during shelter-in-place, we found a ten-fold higher frequency of daily SSB consumption compared to those not facing new financial hardship (2.76 [95% CI: 1.78, 3.74] versus 0.30 [95% CI: 0.23, 0.37] times/day). There were no statistically significant increases in reported purchasing of any SSB, but those with new financial hardship during shelter-in-place reported greater purchasing of regular soda relative to those with no new hardship (0.20 on a 3-point scale [95% CI: 0.03, 0.37]). Our findings suggest that new hardship may increase unhealthy behaviors and worsen existing disparities in SSB consumption. Such disparities are a reminder of the urgent need to reduce economic inequity and improve the quality of our emergency food system in order to mitigate the impact of public health crises like the COVID-19 pandemic.

Weight Measurements in School: Setting and Student Comfort

OBJECTIVE

To examine how body mass index assessments are conducted in schools and whether student comfort with assessments varies by students' perceived weight status, weight satisfaction, or privacy during measurements.

METHODS

In-person cross-sectional surveys with diverse fourth- to eighth-grade students (n = 11,510) in 54 California schools in 2014-2015 about their experience being weighed in the prior school year.

RESULTS

Half of the students (49%) reported being weighed by a physical education teacher and 28% by a school nurse. Students were more comfortable being weighed by nurses than physical education teachers (P = 0.01). Only 30% of students reported privacy during measurements. Students who were unhappy with their weight (P <0.001) and those who perceived themselves as overweight (P <0.001) were less comfortable being weighed than their peers.

CONCLUSIONS AND IMPLICATIONS

Student weight dissatisfaction, higher perceived weight status, and being female were associated with discomfort with school-based weight measurements. Prioritizing school nurses to conduct weight measurements could mitigate student discomfort, and particular attention should be paid to students who are unhappy with their weight to avoid weight stigmatization.

Current Concepts in the Management of Advanced Trigger Finger: A Critical Analysis Review

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While the majority of patients with trigger finger obtain excellent outcomes from nonoperative treatment or release of the A1 pulley, a subset of patients with advanced trigger finger, defined as trigger finger with loss of active or passive range of motion, may have incomplete symptom relief and warrant specific attention.

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Advanced trigger finger is more refractory to complete symptom resolution from corticosteroid injection, and particular attention should be paid to incomplete improvement of flexion contractures.

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Unlike simple trigger finger, the pathology in advanced trigger finger involves not only the A1 pulley but also the flexor tendon, including thickening and degeneration.

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Progression toward surgical intervention should not be delayed when nonoperative measures fail, and specific attention should be paid to persistent inability to achieve full extension following A1 pulley release.

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Facing substantial residual flexion contracture, reduction flexor tenoplasty and partial or complete resection of the superficialis tendon followed by hand therapy and splinting may be needed to allow patients to regain reliable full range of motion.

Secular Trends in Sugar-Sweetened Beverage Consumption Among Adults, Teens, and Children: The California Health Interview Survey, 2011-2018

Consumption of sugar-sweetened beverages (SSBs) contributes to adverse health outcomes and excess health care spending. To provide context for ongoing work assessing the impact of public health strategies, including SSB excise taxes, we used data from the California Health Interview Survey from 2011–2018 to estimate trends in beverage consumption among adults, teens, and children overall and by education, race/ethnicity, and family income. We found reductions in the annual prevalence and frequency of soda consumption across all age groups and heterogeneous increases in the consumption of fruit drinks among adults and children. Surveillance of beverage consumption trends will continue to strengthen and improve the ability of researchers and policy makers to effectively improve population health.

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

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.

Developing drugs for treatment of atopic dermatitis in children (≥3 months to <18 years of age): Draft guidance for industry

Atopic dermatitis is the most common chronic skin disease, and it primarily affects children. Although atopic dermatitis (AD) has the highest effect on burden of skin disease, no high-level studies have defined optimal therapy for severe disease. Corticosteroids have been used to treat AD since the 1950s and remain the only systemic medication with Food and Drug Administration approval for this indication in children, despite published guidelines of care that recommend against this option. Several clinical trials with level 1 evidence have supported the use of topical treatments for mild to moderate atopic dermatitis in adults and children, but these trials have had little consistency in protocol design. Consensus recommendations will help standardize clinical development and trial design for children. The Food and Drug Administration issues guidance documents for industry as a source for "the Agency's current thinking on a particular subject." Although they are nonbinding, industry considers these documents to be the standard for clinical development and trial design. Our consensus group is the first to specifically address clinical trial design in this population. We developed a draft guidance document for industry, Developing Drugs for Treatment of Atopic Dermatitis in Children (≥3 months to <18 years of age). This draft guidance has been submitted to the Food and Drug Administration based on a provision in the Federal Register (Good Guidance Practices).

The ulnar side of the wrist: Clinically relevant anatomy and biomechanics

BACKGROUND

In the hectic environment of a hand therapy clinic, the opportunity to carefully consider the relationships among pathology, pathomechanics, surgical repair techniques, tissue healing, postoperative management, and rehabilitation program development and progression is limited. Clinicians often default to seeking a protocol, a recipe to follow.

OBJECTIVES

Using the ulnar side of the wrist as an example, relevant anatomy and biomechanics are directly related to several commonly seen pathologies, including fractures, ligament injuries, and instability.

CONCLUSION

Armed with knowledge of anatomy, biomechanics, and surgical procedures, the need for a protocol disappears. Each patient can be individually managed according to his or her unique set of variables and responses to injury, repair, healing, and recovery of function.

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.

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.

Expression of an anaplerotic enzyme, pyruvate carboxylase, improves recombinant protein production in Escherichia coli

Anaplerotic enzyme reactions are those which replenish tricarboxylic acid intermediates that are withdrawn for the synthesis of biomass. In this study, we examined recombinant protein production in Escherichia coli containing activity in an additional anaplerotic enzyme, pyruvate carboxylase. In batch fermentations, the presence of pyruvate carboxylase resulted in 68% greater production of the model protein, beta-galactosidase, 41% greater cell yield, and 57% lower acetate concentration. We discuss why these results indicate that acetate concentration does not limit cell growth and protein synthesis, as predicted by other researchers, and suggest instead that the rate of acetate formation represents an inefficient consumption of glucose carbon, which is reduced by the presence of pyruvate carboxylase.