Modulation of physiological responses with TiO<Subscript>2</Subscript> nano-particle in <Emphasis Type="Italic">Azolla pinnata</Emphasis> R.Br. under 2,4-D toxicity

The present work is emphasised with the herbicidal tolerance of Azolla pinnata R.Br. and its modulation with TiO₂ nano-particle. Both carbohydrate and nitrogen metabolism were effected with 2,4-D as herbicide and in few cases TiO₂-NP had recovered few detrimental effects. From the nutrient status in Azolla it recorded the recovery of nitrogen as well as potassium by TiO₂-NP but not in case of phosphorus. However, a conversion of nitrate to ammonium was more induced by TiO₂-NP under herbicidal toxicity. Similar results were obtained for inter-conversion of amino acid–nitrate pool, but no changes with glutamine synthase activity with TiO₂-NP. Initially, the effects of 2,4-D was monitored with changes of chlorophyll content but had not been recovered with nanoparticle. Photosynthetic reserves expressed as both total and reducing sugar were insensitive to TiO₂-NP interference but activity of soluble and wall bound invertase was in reverse trend as compared to control. The 2,4-D mediated changes of redox and its oxidative stress was ameliorated in plants with over expressed ADH activity. As a whole the Azolla bio system with TiO₂ supplementation may be useful in sustenance against 2,4-D toxicity through recovery of nitrogen metabolism. Thus, Azolla-TiO₂-NP bio system would be realised to monitor the herbicidal toxicity in soil and its possible bioremediation.     

Stoichiometric model of Escherichia coli metabolism: incorporation of growth-rate dependent biomass composition and mechanistic energy requirements

A stoichiometric model of metabolism was developed to describe the balance of metabolic reactions during steady-state growth of Escherichia coli on glucose (or metabolic intermediates) and mineral salts. The model incorporates 153 reversible and 147 irreversible reactions and 289 metabolites from several metabolic data bases for the biosynthesis of the macromolecular precursors, coenzymes, and prosthetic groups necessary for synthesis of all cellular macromolecules. Correlations describing how the cellular composition changes with growth rate were developed from experimental data and were used to calculate the drain of precursors to macromolecules, coenzymes, and prosthetic groups from the metabolic network for the synthesis of those macromolecules at a specific growth rate. Energy requirements for macromolecular polymerization and proofreading, transport of metabolites, and maintenance of transmembrane gradients were included in the model rather than a lumped maintenance energy term. The underdetermined set of equations was solved using the Simplex algorithm, employing realistic objective functions and constraints; the drain of precursors, coenzymes, and prosthetic groups and the energy requirements for the synthesis of macromolecules served as the primary set of constraints. The model accurately predicted experimentally determined metabolic fluxes for aerobic growth on acetate or acetate plus glucose. In addition, the model predicted the genetic and metabolic regulation that must occur for growth under different conditions, such as the opening of the glyoxylate shunt during growth on acetate and the branching of the tricarboxylic acid cycle under anaerobic growth. Sensitivity analyses were performed to determine the flexibility of pathways and the effects of different rates and growth conditions on the distribution of fluxes. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 398-421, 1997.     

Lung and alveolar wall elastic and hysteretic behavior in rats: effects of in vivo elastase treatment.

We investigated the relationship between the microscopic elastic and hysteretic behavior of the alveolar walls and the macroscopic mechanical properties of the whole lung in an in vivo elastase-treated rat model of emphysema. We measured the input impedance of isolated lungs at three levels of transpulmonary pressure (Ptp) and used a linear model to estimate the dynamic elastance and hysteresivity of the lungs. The elastance of the normal lungs increased steeply with Ptp, whereas this dependence diminished in the treated lungs. Hysteresivity decreased significantly with Ptp in the normal lungs, but this dependence disappeared in the treated lungs. To investigate the microscopic origins of these changes, the alveolar walls were immunofluorescently labeled in small tissue strips. By using a fluorescent microscope, the lengths and angular orientations of individual alveolar walls were followed during cyclic uniaxial stretching of the tissue strips. The microstrains (relative change in segment length) and changes in angle of the alveolar walls showed considerable heterogeneity, which was interpreted in terms of a network model. In the normal strips, the alveolar walls showed larger angular changes compared with the treated tissue, whereas the alveolar walls of the treated tissue tended to be more extensible. Hysteresis in the average angle change was also larger in the treated tissue than in the normal tissue. We conclude that the decreased Ptp dependence of elastance and the constant hysteresivity in the treated lungs are related to microstructural remodeling and network phenomena at the level of the alveolar walls.     

Effect of superparasitism on the development,sex ratio and progeny ofBracon greeni Ashmead

Résumé Bracon greeni Ashmead est un ectoparasite larvaire de la noctuelleEublemma amabilis Moore, prédatrice sur laquiers en Inde. L'effet de superparasitisme sur le développement, le sex ratio et la descendance du parasite ont été étudiés en détail. Le pourcentage de développement du parasite décro?t quand le nombre de parasites développés par h?te augmente. La période de développement, de l'œuf à l'éclosion de l'adulte, est de 10, 85 jours et ce délai est un peu plus court quand l'h?te est fortement superparasité. La taille de la femelle adulte décro?t avec l'augmentation du nombre de parasites développés par h?te. Il y a prédominance du sexe femelle chez le parasite. Le superparasitisme ne para?t avoir que peu d'action sur le taux sexuel. Quand plus de trois parasites se partagent un seul h?te, la longévité de l'adulte et la fécondité du parasite sont réduits. De tels individus sont mauvais voiliers et inactifs dans leur comportement.      

Ribosome hibernation factor promotes Staphylococcal survival and differentially represses translation

In opportunistic Gram-positive Staphylococcus aureus, a small protein called hibernation-promoting factor (HPF_Sa) is sufficient to dimerize 2.5-MDa 70S ribosomes into a translationally inactive 100S complex. Although the 100S dimer is observed in only the stationary phase in Gram-negative gammaproteobacteria, it is ubiquitous throughout all growth phases in S. aureus. The biological significance of the 100S ribosome is poorly understood. Here, we reveal an important role of HPF_Sa in preserving ribosome integrity and poising cells for translational restart, a process that has significant clinical implications for relapsed staphylococcal infections. We found that the hpf null strain is severely impaired in long-term viability concomitant with a dramatic loss of intact ribosomes. Genome-wide ribosome profiling shows that eliminating HPF_Sa drastically increased ribosome occupancy at the 5′ end of specific mRNAs under nutrient-limited conditions, suggesting that HPF_Sa may suppress translation initiation. The protective function of HPF_Sa on ribosomes resides at the N-terminal conserved basic residues and the extended C-terminal segment, which are critical for dimerization and ribosome binding, respectively. These data provide significant insight into the functional consequences of 100S ribosome loss for protein synthesis and stress adaptation.     

Molecular oxygen dependent steps in fatty acid oxidation by cyclooxygenase-1

The mechanism by which cyclooxygenase-1 (COX-1), a heme- and tyrosyl radical-containing enzyme, catalyzes the regio- and stereospecific oxygenation of polyunsaturated fatty acids to prostaglandin or hydroperoxide products has not been understood. Steady-state kinetic studies conducted with the native substrate arachidonic acid and the slower substrate linoleic acid are described here. Second-order rate constants, kcat/KM for fatty acid and O2, are found to depend upon the concentration of the other cosubstrate. Competitive oxygen kinetic isotope effects (18O KIEs) kcat/KM(16,16O2)/kcat/KM(18,16O2) reveal that a peroxyl radical is formed in or before the first kinetically irreversible step. Together, the results indicate that the oxygenase reaction occurs by a sequential mechanism which most likely involves reversible abstraction of a hydrogen atom from the fatty acid prior to the trapping of the delocalized substrate radical by O2. The identity of the first kinetically irreversible step, subsequent to forming the peroxyl radical, is also discussed in the context of the magnitude of the oxygen kinetic isotope effects as well as the behavior of kcat/KM(O2) in response to changing solvent pH, pD, and viscosity.     

Low-dose whole thorax radiation therapy for COVID-19 pneumonia: inpatient onboarding process for a randomized controlled trial

BackgroundThe mortality of the SARS-CoV-2 virus (COVID-19) has been associated with a pulmonary inflammatory response resulting in hypoxemia and rapid clinical decline. PREVENT is an ongoing prospective multicenter Phase II randomized controlled trial where patients hospitalized with COVID-19 pneumonia are randomized to low dose radiation therapy (RT) versus control (clinicaltrials.gov, {"type":"clinical-trial","attrs":{"text":"NCT04466683","term_id":"NCT04466683"}}NCT04466683). We describe the inpatient onboarding process of the center contributing the largest number of patients to this trial.Materials and methodsCOVID-19 hospital admissions were attained by the clinical research manager and radiation oncologist daily. Text message contact was made with infectious disease, critical care, and nursing staff with reciprocal discussion of the trial protocol and approval for virtual consulting of the patient. Witnessed informed consent was obtained first by telephone and later in person. Simulation and treatment (performed without a computer plan) was performed on a linear accelerator with one personal protective equipment-protected therapist moving in and out of the treatment room, and a second therapist manning the console. Following on-site dose calculation by physics, the radiation oncologist approved the fields prior to treatment delivery.ResultsBetween August 28, 2020 and October 6, 2020, the first 10 enrolled patients on this multicenter trial were randomized and treated at our institution; no team member (research staff, radiation oncology) contracted COVID-19 while employing this protocol.ConclusionThis represents the first published protocol to address efficient and safe recruitment of COVID-19 patients for a radiation oncology trial, serving as a model for conducting recruitment of COVID-19 patients for clinical trials.