scholarly journals Simulation of the apparent diffusion of helium-3 in the human acinus

2007 ◽  
Vol 103 (1) ◽  
pp. 249-254 ◽  
Author(s):  
Sylvia Verbanck ◽  
Manuel Paiva
Keyword(s):  
Initial Conditions ◽  
Model Structure ◽  
Point Model ◽  
Free Diffusion ◽  
Time Intervals ◽  
Hyperpolarized Helium ◽  
Lung Structure ◽  
Peripheral Structure ◽  
Apparent Diffusion

Functional MRI of the lungs with hyperpolarized helium provides an index of apparent diffusion measured over several seconds (ADCsec) that is only 2% of its free diffusion in air (0.88 cm2/s). The potential of ADCsec to noninvasively assess in vivo lung structure of diseased lungs at the length scales corresponding to several seconds is critically dependent on the exact link between ADCsec and lung peripheral structure. To understand the intruigingly small ADCsec, numerical simulations of gas transport were performed in 1) a trumpet model, 2) a symmetrical, and 3) an asymmetrical multiple-branch-point model of the human acinus. For initial gas boluses in different locations of the acinar models, ADCsec was quantified as follows. At different time intervals, we computed a coefficient of variation (CoV) of the concentration distributions within each acinar model. The slope in the semilog plot of log(CoV) vs. time was proportional to the ADCsec generated by the internal model structure, provided that the outer model boundaries were similar across all models (i.e., similar cumulative cross section vs. average path length). The simulations revealed an ADCsec that amounted to ∼1% of free diffusion in the trumpet model of the acinus, i.e., corresponding to free diffusion within the acinar geometric boundaries. Our simulations show that for initial conditions corresponding to those used in MRI experiments, intra-acinar branching introduces a dramatic diffusion delay, comparable to what is observed experimentally.

Assessment of in vitro vs. in vivo lung structure using hyperpolarized helium-3 diffusion magnetic resonance imaging

2009 ◽  
Vol 27 (6) ◽  
pp. 845-851 ◽  
Author(s):  
Jaime F. Mata ◽  
Talissa A. Altes ◽  
Kai Ruppert ◽  
Klaus D. Hagspiel ◽  
Grady W. Miller ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Diffusion Magnetic Resonance Imaging ◽  
Resonance Imaging ◽  
Hyperpolarized Helium ◽  
Lung Structure ◽  
Helium 3

Synaptic Interactions Between Thalamic and Cortical Inputs Onto Cortical Neurons In Vivo

2004 ◽  
Vol 91 (5) ◽  
pp. 1990-1998 ◽  
Author(s):  
Pablo Fuentealba ◽  
Sylvain Crochet ◽  
Igor Timofeev ◽  
Mircea Steriade
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Input Resistance ◽  
Maximal Effect ◽  
Time Intervals ◽  
Neocortical Neurons ◽  
Synaptic Interactions ◽  
Cortical Responses ◽  
Cortical Inputs

To study the interactions between thalamic and cortical inputs onto neocortical neurons, we used paired-pulse stimulation (PPS) of thalamic and cortical inputs as well as PPS of two cortical or two thalamic inputs that converged, at different time intervals, onto intracellularly recorded cortical and thalamocortical neurons in anesthetized cats. PPS of homosynaptic cortico-cortical pathways produced facilitation, depression, or no significant effects in cortical pathways, whereas cortical responses to thalamocortical inputs were mostly facilitated at both short and long intervals. By contrast, heterosynaptic interactions between either cortical and thalamic, or thalamic and cortical, inputs generally produced decreases in the peak amplitudes and depolarization area of evoked excitatory postsynaptic potentials (EPSPs), with maximal effect at ∼10 ms and lasting from 60 to 100 ms. All neurons tested with thalamic followed by cortical stimuli showed a decrease in the apparent input resistance ( Rin), the time course of which paralleled that of decreased responses, suggesting that shunting is the factor accounting for EPSP's decrease. Only half of neurons tested with cortical followed by thalamic stimuli displayed changes in Rin. Spike shunting in the thalamus may account for those cases in which decreased synaptic responsiveness of cortical neurons was not associated with decreased Rin because thalamocortical neurons showed decreased firing probability during cortical stimulation. These results suggest a short-lasting but strong shunting between thalamocortical and cortical inputs onto cortical neurons.

scholarly journals Differences in the metabolism of esterified and unesterified linoleic acid by rumen micro-organisms

1969 ◽  
Vol 23 (4) ◽  
pp. 869-878 ◽  
Author(s):  
J. H. Moore ◽  
R. C. Noble ◽  
W. Steele ◽  
J. W. Czerkawski
Keyword(s):  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Linoleic Acid ◽  
Stearic Acid ◽  
Octadecenoic Acid ◽  
Time Intervals ◽  
Micro Organisms ◽  
Hydrolysis Of ◽  
Maize Oil

1. Sheep were given intraruminal infusions of maize oil or linoleic acid and samples of contents were taken from the rumen and abomasum at different times after the infusions. Hydrolysis of the maize oil occurred in the rumen with the production of mono- and di-glycerides as intermediates. Linoleic acid derived from the maize oil was hydrogenated to stearic acid. When linoleic acid was infused into the rumen, little or no stearic acid was produced and octadecenoic acid accumulated.2. When linoleic acid or maize oil was incubated with rumen contents in an artificial rumen and samples of the reaction mixtures were taken from the apparatus after various time intervals, the results were similar to those obtained in vivo, except that the hydrolysis of maize oil did not give rise to mono- and di-glycerides.3. These results are discussed in relation to previous findings on the effects of intraruminal infusions of maize oil or linoleic acid on the fatty acid composition of the blood triglycerides of sheep.

In vivo effects of N/OFQ(1–13)NH2 and its structural analogue [ORN9]N/OFQ(1–13)NH2 on carrageenan-induced inflammation: rat-paw oedema and antioxidant status

2009 ◽  
Vol 4 (2) ◽  
pp. 170-178 ◽  
Author(s):  
Rositsa Zamfirova ◽  
Elina Tzvetanova ◽  
Albena Alexandrova ◽  
Lubomir Petrov ◽  
Polina Mateeva ◽  
...  
Keyword(s):  
Antioxidant Status ◽  
Time Intervals ◽  
Structural Analogue ◽  
Paw Oedema ◽  
The Right ◽  
Rat Paw ◽  
Induced Changes ◽  
In Vivo Effects ◽  
Rat Paw Oedema

AbstractThe effects of nociceptin(1–13)NH2 (N/OFQ(1–13)NH2) and its structural analogue [Orn9]N/OFQ(1–13)NH2 on acute carrageenan (CG)-induced peripheral inflammation and paw antioxidant status were studied. CG was injected intraplantarly in the right hind paw of rats and the volume of the inflamed paw was measured each 30 min for a period of 4h. When administered simultaneously with CG, N/OFQ(1–13)NH2 decreased the paw volume, whereas if injected 15 min before CG it had no effect. [Orn9]N/OFQ(1–13)NH2 produced the opposite effects at the same time-intervals of its administration. We also investigated whether these neuropeptides influence CG-induced changes in cell antioxidant system, especially at the 4th hour of CG administration. CG alone decreased the glutathione level and superoxide dismutase activity, as measured in post-nuclear homogenate of the inflamed paw. However, CG injection increased glutathione peroxidase and glucose-6-phospate dehydrogenase activities, while the activity of glutathione reductase was unchanged. The peptides themselves did not change all measured parameters. Moreover, neither N/OFQ(1–13)NH2 nor [Orn9]N/OFQ(1–13)NH2 modified CG-induced changes in the antioxidant status, regardless of the time of their injection (simultaneously or 15 min before CG). The present results suggest that N/OFQ(1–13)NH2 and [Orn9]N/OFQ(1–13)NH2 most likely affect the neuronal inflammation, rather than act as pro- or antioxidants.

A Method for Quantitative Analysis of the Kinematics of Fibroblast Migration in a Monolayer Wound Model

2011 ◽  
Author(s):  
Gil Topman ◽  
Orna Sharabani-Yosef ◽  
Amit Gefen
Keyword(s):  
Wound Healing ◽  
Cell Migration ◽  
Wound Healing Assay ◽  
Complete Coverage ◽  
Time Intervals ◽  
Fibroblast Migration ◽  
Wound Model ◽  
Regular Time

A wound healing assay is simple but effective method to study cell migration in vitro. Cell migration in vitro was found to mimic migration in vivo to some extent [1,2]. In wound healing assays, a “wound” is created by either scraping or mechanically crushing cells in a monolayer, thereby forming a denuded area. Cells migrate into the denuded area to complete coverage, and thereby “heal” the wound. Micrographs at regular time intervals are captured during such experiments for analysis of the process of migration.

scholarly journals Modelling the impact of the macroalgae Asparagopsis taxiformis on rumen microbial fermentation

2020 ◽  
Author(s):  
Rafael Muñoz-Tamayo ◽  
Juana C. Chagas ◽  
Mohammad Ramin ◽  
Sophie J. Krizsan
Keyword(s):  
Methane Production ◽  
Volatile Fatty Acids ◽  
Mean Squared Error ◽  
Microbial Fermentation ◽  
Model Structure ◽  
Red Macroalgae ◽  
Asparagopsis Taxiformis ◽  
The Impact

AbstractBackgroundThe red macroalgae Asparagopsis taxiformis is a potent natural supplement for reducing methane production from cattle. A. taxiformis contains several anti-methanogenic compounds including bromoform that inhibits directly methanogenesis. The positive and adverse effects of A. taxiformis on the rumen microbiota are dose-dependent and operate in a dynamic fashion. It is therefore key to characterize the dynamic response of the rumen microbial fermentation for identifying optimal conditions on the use of A. taxiformis as a dietary supplement for methane mitigation. Accordingly, the objective of this work was to model the effect of A. taxiformis supplementation on the rumen microbial fermentation under in vitro conditions. We adapted a published mathematical model of rumen microbial fermentation to account for A. taxiformis supplementation. We modelled the impact of A. taxiformis on the fermentation and methane production by two mechanisms, namely (i) direct inhibition of the growth rate of methanogenesis by bromoform and (ii) hydrogen control on sugars utilization and on the flux distribution towards volatile fatty acids production. We calibrated our model using a multi-experiment estimation approach that integrated experimental data with six macroalgae supplementation levels from a published in vitro study assessing the dose-response impact of A. taxiformis on rumen fermentation.Resultsour model captured satisfactorily the effect of A. taxiformis on the dynamic profile of rumen microbial fermentation for the six supplementation levels of A. taxiformis with an average determination coefficient of 0.88 and an average coefficient of variation of the root mean squared error of 15.2% for acetate, butyrate, propionate, ammonia and methane.Conclusionsour results indicated the potential of our model as prediction tool for assessing the impact of additives such as seaweeds on the rumen microbial fermentation and methane production in vitro. Additional dynamic data on hydrogen and bromoform are required to validate our model structure and look for model structure improvements. We are working on model extensions to account for in vivo conditions. We expect this model development can be useful to help the design of sustainable nutritional strategies promoting healthy rumen function and low environmental footprint.

scholarly journals Chitosan from Lucilia cuprina (Diptera: Calliphoridae) enhances sensitization to insulin treatment in a diabetic burn mice of wound healing

2020 ◽  
Vol 1 (1) ◽  
pp. 1-15
Author(s):  
Lamia M. El-Samad ◽  
◽  
Azza A. Attia ◽  
Basant A. Bakr ◽  
◽  
...  
Keyword(s):  
Wound Healing ◽  
Wound Closure ◽  
Lucilia Cuprina ◽  
Diabetic Mice ◽  
Burn Wound ◽  
Time Intervals ◽  
Burn Wound Healing ◽  
High Degree

Chitosan is recognized as a multipurpose biomaterial because of its low allergenicity, non-toxicity, biodegradability and biocompatibility. The present study was designed to estimate the role of chitosan derived from Lucilia cuprina on burn healing in diabetic mice; using histopathological and microbiological studies at different time intervals. Chitosan was prepared from L. cuprina with high molecular weight (MW) and high degree of deacetylation (DD) to evaluate its burn wound healing potential; skin burn closure assessment, histological and microbiological studies in vivo in male diabetic mice. Chitosan topical treatment was superior in wound closure acceleration; mainly in insulin injected group at all the time intervals. Additionally, earlier epidermal remodelling with mature and intense collagen deposition was encountered in all chitosan treated animals as well as non-diabetic burned animals. There was a significant delay in hair growth and poor epidermal remodelling with impairment of wound closure in diabetic groups. Moreover, chitosan treated groups assert the chitosan antibacterial effects with protecting the burn against contamination that hinders healing especially in this diabetic condition. Further researches needed to interpret effects of possible synergistic combination therapy.

On a Certain Class of Expanding Systems

2010 ◽  
Vol 17 (2) ◽  
pp. 299-306
Author(s):  
Adam Żuchowski
Keyword(s):  
Transfer Function ◽  
Input Signal ◽  
Initial Conditions ◽  
System Optimization ◽  
Gain Coefficient ◽  
Time Intervals ◽  
System Parameters ◽  
Linear Dynamic ◽  
Subsequent Time ◽  
Input Signals

On a Certain Class of Expanding Systems The interesting properties of a class of expanding systems are discussed. The operation of the considered systems can be described as follows: the input signal is processed by a linear dynamic converter in subsequent time intervals, each of them is equal to Ti. Processing starts at the moments n · Ti, always after zeroing of converter initial conditions. For smooth input signals and a given transfer function of the converter one can suitably choose Ti and the gain coefficient in order to realize the postulated linear operations on input signals, which is quite different comparing it to the operation realized by the converter. The errors of postulated operations are mainly caused by non-smooth components of the input signal. The principles for choice of system parameters and rules for system optimization are presented in the paper. The referring examples are attached too.

scholarly journals Studies in vivo on the biosynthesis of collagen and elastin in ascorbic acid-deficient guinea pigs. Evidence for the formation and degradation of a partially hydroxylated collagen

1970 ◽  
Vol 119 (3) ◽  
pp. 575-585 ◽  
Author(s):  
M. J. Barnes ◽  
B. J. Constable ◽  
L. F. Morton ◽  
E. Kodicek
Keyword(s):  
Molecular Weight ◽  
Ascorbic Acid ◽  
Guinea Pigs ◽  
Specific Radioactivity ◽  
Rapid Decline ◽  
Time Intervals ◽  
Skin Collagen ◽  
Labelled Compound ◽  
Degree Of Degradation

1. After the administration of l-[G-3H]proline to guinea pigs deprived of ascorbic acid for increasing periods of time, the specific radioactivities of proline and hydroxyproline in skin collagen and aortic elastin were determined at various time-intervals after administration of the labelled compound with a view to studying the formation and degradation of collagen and elastin both deficient in hydroxyproline. 2. As judged from the incorporation of radioactivity into elastin proline, elastin synthesis was not decreased in the ascorbic acid-deficient animals. There was however, a rapid decline in the specific radioactivity of elastin hydroxyproline. The proline/hydroxyproline specific-radioactivity ratio was approx. 1.5:1 after 6 days and 20:1 after 12 days of ascorbic acid deprivation, in contrast with the ratio of 1:1 in controls. The results suggested that the effect of ascorbic acid deficiency on elastin biosynthesis could be regarded as simply an elimination of hydroxylation of elastin proline with the formation and retention of a polymer increasingly deficient in hydroxyproline. 3. Collagen proline and hydroxyproline specific radioactivities were derived from material that was soluble in hot trichloroacetic acid, non-diffusible and collagenase-degradable. In contrast with elastin, there was a rapid decline in the specific radioactivity of proline as well as hydroxyproline in collagen from the ascorbic acid-deficient animals. However, the proline/hydroxyproline specific-radioactivity ratio in all samples from scorbutic animals was consistently slightly above 1:1. The results suggest the appearance in place of collagen, but in rapidly diminishing amounts, of a partially hydroxylated collagen in which the degree of hydroxylation may be decreased only by approx. 10%. 4. Incorporation of radioactivity into the diffusible hydroxyproline in skin remained relatively high despite the rapid decline in the incorporation of radioactivity into collagen. This observation is interpreted as indicative of an increasing degree of degradation of partially hydroxylated collagen to diffusible peptides. An alternative explanation might be that partially hydroxylated peptides are released to an increasing extent from ribosomes before they attain a length at least sufficient to render them non-diffusible. In either case it implies the accumulation in scurvy of low-molecular-weight peptides enriched in proline and deficient in hydroxyproline and could explain the failure to accumulate a high-molecular-weight collagen deficient in hydroxyproline. 5. It is thought, however, that, in addition, an inhibition of ribosomal amino acid incorporation leading to decreased synthesis of partially hydroxylated collagen may also occur, perhaps secondarily to impaired hydroxylation.

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