Passive Compartment Research Articles

Simulating soil carbon and nitrogen trends under an integrated system in the Brazilian Cerrado

Management systems that include trees tend to provide higher amounts of plant biomass to the soil, contributing to the increase in carbon (C) and nitrogen (N) stocks. This study simulated C and N stocks and their compartments in a crop-livestock-forest integration system in the edafoclimatic conditions of the Maranhão Cerrado using the Century 4.5 model. The evaluated areas were native Cerrado vegetation (NV) and crop-livestock-forest integration (CLFI). The calibration process gradually modified the model parameters to better fit the simulated and observed soil C and N stocks. The best fit between the data was obtained after changes in the main parameters (DEC3(2), DEC4, and DEC5) that controlled the rate of decomposition of soil organic matter. C and N stocks increased by 14% and 15%, respectively, over 14 years after replacing NV with CLFI. The slow compartment of C presented greater sensitivity to changes in management, with an increase of 47% compared with that of NV. The active compartment increased by 31% and the passive compartment remained constant for over 14 years. Future scenarios, where pasture was maintained between the eucalyptus trees and the scenario that allowed the soybean, corn, and Brachiaria rotation between the trees, were more effective, accumulating approximately 37 Mg C ha-1. The continuous contribution of residues from the trees and pasture increased C and N stocks in the long-term in the slow fraction, where the total organic carbon increased from 32 to 36 Mg ha-1 when NV was replaced with CLFI. The model predicted the C and N stocks with accuracies ranging from 1 to 11% of the observed values

Qualitative and Quantitative Characteristics of the Passive Compartment Underneath the Myocardial Bridge Comprising the Blood Vessel Adventitia and the Perivascular Connective Tissue

Myocardial bridges are inborn anomalies frequently found in authopsies. Although tipically clinically silent, they are occasionally associated with severe clinical manifestations, e.g. myocardial ischemia or even sudden death. The pathophysiology and risk factors for these manifestations have not yet been completely elucidated. The connective tissue underneath the bridge has been considered as one of the factors the symptoms depend on. Thus, the aim of this research was to determine the histological characteristics of the connective tissue lying underneath the myocardial bridge and to contribute to a better understanding of the protective effects this passive compartment might have in prevention of severe clinical manifestations of myocardial bridging. The study was carried out on twenty hearts with myocardial bridges. Length of the bridge was determined using a precise electronic caliper. Sections of the myocardial bridges with the underlying connective tissue were obtained and prepared for qualitative and quantitative analysis. The connective tissue underneath the bridges was composed of adipose tissue and loose connective tissue in different ratios. The tissue underneath thin bridges was predominantly composed of adipose tissue, while loose connective tissue was the dominant component under thick bridges. The myocardial bridges had an average thickness of 0,98 ± 0.44 mm and an average length of 15,25±5,65 mm. We found a strong positive correlation between the myocardial bridge thickness and length (r = 0,860, p = 0,0001). The thickness of the passive connective tissue compartment under the myocardial bridges was 0,58±0,22 mm, and there was no correlation between this parameter and the myocardial bridge thickness (r = -0,011; p = 0,963). In the clinical evaluation of patients with these anomalies it is necessary to take into account independently the myocardial bridge thickness and length on one side and the thickness of the connective tissue lying underneath it on the other.

Testing two behavioural paradigms for measuring post-handling cat aversion behaviour

Owned, shelter, and laboratory cats undergo handling and restraint throughout their lifetime for routine health examinations and necessary procedures. Many cats display fear and aggressive behaviour during health examinations, and there is potential for these behaviours to result in incomplete examination, and inadequate diagnosis and treatment, which are cat welfare concerns. Given the lack of validated methods to assess cat responses to restraint, the current study aimed to validate two behavioural paradigms: 1) a Handler Aversion Test, and 2) a Conditioned Place Aversion (CPA) test, to assess aversion response differences between passive restraint (the control) and full-body restraint (known to be negative). Cats were initially assessed as either friendly or unfriendly during interactions with a stranger, and this was included as a covariate in analyses. During the Handler Aversion Test, cats were restrained with the passive (n = 20) or full-body (n = 18) restraint, and aversion was assessed by measuring cat latency to approach the handler. CPA testing was carried out separately in laboratory (n = 10) and shelter (n = 42) cats using an apparatus made up of two visually-distinct compartments: cats were handled with passive restraint on one side, and full-body restraint on the other side, with handling methods counter-balanced between compartments. After handling, cats were placed into the apparatus and dwelling time was assessed for each compartment. For the Handler Aversion Test, only 38 out of 51 cats could be trained to walk the required runway, and latency to approach the handler was not significantly different between treatments (P > 0.1). During CPA testing, laboratory cats and friendly shelter cats showed aversion towards the full-body restraint compartment, spending most of their time in the passive compartment (P = 0.043, P = 0.035, respectively); a result not seen in unfriendly shelter cats. The current results suggest that, as assessed in the current study, the CPA test is more sensitive than the Handler Aversion Test for detecting differences in cat aversion responses between a known negative and control restraint technique.

English

The use of mathematical models is an alternative way to understand how management practices affect soil organic matter (SOM) dynamics because such models yield results on time scales that would be impossible to observe in field studies. The aim of this study was to parameterise and calibrate the application Century 4.0 in terms of the edaphoclimatic conditions of a Latossolo Vermelho-Amarelo of the Araripe Plateau and simulate the soil C dynamics in each compartment. The study was conducted in the Araripe National Forest (Floresta Nacional do Araripe ― FLONA). The soils are classified as Latossolos Vermelho-Amarelos with a medium clayey texture and a clay fraction consisting of kaolinite with iron and aluminium oxides. The physical and chemical properties of the soils were obtained at a depth of 0.00-0.20 m in 2012 and 2013. The best total organic carbon (TOC) result was an error of only 3% between the measured and simulated values, which was obtained with a PRDX (4) adjustment of 140 g m-2 C. After correcting for the C decay rate in the passive (PC), slow (SC) and active compartments (AC), absolute errors lower than 10% were obtained for the C values. The abiotic correction factors specific to each compartment were 0.89 for the active and passive compartments and 1.12 for the slow compartment. The sensitivity analysis indicates that all compartments are sensitive to variations in maximum and minimum temperature and that the clay content affects the TOC and the passive compartment.   Key words: Century model calibration, soil carbon compartments.

Cell confinement: putting the squeeze on the nucleus

The nucleus has long been considered as a passive compartment containing the genetic information. However, recent attention to its structure, mechanical properties and physical connections with other cellular compartments has shown that the nucleus changes dynamically its morphology and internal organization for important cellular processes, especially those associated with cellular confinement. In this paper, we review some recent progress in experimental investigations of nuclear squeezing that lead to a better understanding of the nuclear remodeling in response to various situations of cellular confinement. We will discuss compelling examples of original experiments performed with microsystems that have recently brought new insights into the close relationship between nuclear mechanics and cellular organization. We will show that the study of nuclear confinement with microsystems has opened up new experimental avenues that already offer promising clues for understanding diseases that are associated with defective nuclear mechanics.

The Chloroplast Outer Envelope Membrane: The Edge of Light and Excitement

Abstract The chloroplast is surrounded by a double‐membrane envelope at which proteins, ions, and numerous metabolites including nucleotides, amino acids, fatty acids, and carbohydrates are exchanged between the two aqueous phases, the cytoplasm and the chloroplast stroma. The chloroplast envelope is also the location where the biosynthesis and accumulation of various lipids take place. By contrast to the inner membrane, which contains a number of specific transporters and acts as the permeability barrier, the chloroplast outer membrane has often been considered a passive compartment derived from the phagosomal membrane. However, the presence of galactoglycerolipids and β‐barrel membrane proteins support the common origin of the outer membranes of the chloroplast envelope and extant cyanobacteria. Furthermore, recent progress in the field underlines that the chloroplast outer envelope plays important roles not only for translocation of various molecules, but also for regulation of metabolic activities and signaling processes. The chloroplast outer envelope membrane offers various interesting and challenging questions that are relevant to the understanding of organelle biogenesis, plant growth and development, and also membrane biology in general.

Simulation of a vertebrate receptor cell of the olfactory epithelium for use in network models

We developed a realistic model of a bipolar receptor cell of the olfactory epithelium. It has four compartments, namely cilia, dendritic knob, dendrite and soma. Cilia is a biochemical compartment including the molecular pathways of odor interpretation; dendrite is a passive compartment without channels; dendritic knob has Ca 2+-dependent chloride channels; and soma has all channels of Traub's CA3 hippocampal pyramidal neuron model plus Moczydlowski–Latorre's BK channel model. A pool of molecular odors, which increase Ca 2+ intracellular concentration and conductance of chloride channels, provides the input. The model's bursting behavior compares well with experimental data found in literature.

Long term 15N studies in a catena of the shortgrass steppe

A set of long term15N studies was initiated during the summers of 1981 and 1982 on the backslope and footslope, respectively, of a catena in the shortgrass steppe of northeastern Colorado. Microplots labeled with15N urea were sampled for15N and total N content in 1981 and 1982 and again in 1992. In November, 1982, 100% of the added N was recovered in the soil-plant system of the finer-textured footslope, compared to 39% in the coarser-textured backslope microplots. Ten years later,15N recovery of the applied N decreased at both topographic positions to 85% in the footslope and 29% in the backslope. Average losses since the time of application were 3.5 g N m−2yr−1 in the backslope and 0.8 g N m−2yr−1 in the footslope. In 1992, soil organic matter was physically fractionated into particulate (POM) and mineral associated (MAON) fractions and 21-day mineralization incubations were conducted to assess the relative amounts of15N that were in the slow, passive and active soil organic matter pools, respectively, of the two soils. Our findings confirm the assumptions that POM represents a large portion of the slow organic compartment and that the MAON represents a large fraction of the passive compartment defined in the Century model. The N located in the MAON had the lowest availability for plant uptake. Isotopic data were consistent with textural effects and with the Century model compartmentalization of soil organic N based on the residence time of the organic N.

Intérêt vectocardiographique du dispositif de Boothroyd

Analysing the function of the instrument described by Boothroyd and coworkers, allows to understand how a finite isomorph can be substituted for an infinite extension of a conducting medium. First, we show the consistency between the results obtained from the resistive network and from the mathematical model which are equivalent to the electrolytic tank originally proposed. Among our observations, we underline the one reporting that the zero equipotential always reaches the isomorph center at least when the conductivity is the same in the passive compartment and in the activated disk energized by a dipole of any position. The potential differences picked up around the isomorph center are well suited to a vectorcardiographic application such as Rijlant's one. A simultaneous use of the integration of the potential on the boundary by means of the Gabor & Nelson method provides the reference to which the vectorcardiographic approximation can be compared and so, leads to objectively probe the practical merits of the latter approximation. For instance, at the attenuation level used by Rijlant, the vectorcardiogram images within a 1 % relative error, the magnitude and the orientation changes of a dipole rotating on a pivot the eccentricity of which amounts to 0.5 R. Our validation of Rijlant's method in the conducting systems with radial symmetry from which he started, is the first step in fully anwering Bürger who called for such a proof in his celebrated book on heart and vector.

Kinetics of D-aspartic acid release from rat cortical synaptosomes.

A kinetic study has been made of the release of D-aspartate from rat cortical synaptosomes following pre-loading with labelled D-aspartate, and the results compared to a previous study of the release of the acidic amino acids glutamate plus aspartate following pre-loading with labeled L-glutamate. Qualitatively, the results of the two studies are similar. The D-aspartate taken up during the pre-load period appears to be totally releasable. However, release is greatly increased by depolarizing media. The increased rate of release induced by increasing [K]o is independent of the [Ca]o, while veratrine-induced release is inhibited by [Ca]o. Release is from more than a single compartment, since plots of the log10 of the synaptosomal D-aspartate content (calculated from the label content) as a function of the incubation time are non-linear for all incubation solutions. In the previous study which utilized L-glutamate pre-loading, the results were consistent with either a model consisting of two passive compartments (that is, synaptosomal content T as a function of time is given by Ae-Kat + Be-Kbt, in which A and B are compartment sizes, Ka and Kb are exchange constants, and t is incubation time) or a model consisting of one passive compartment (Ae-Kat) and one saturated carrier compartment (T-Kbt, in which T = total content at zero time and Kb = maximal velocity). The present results with D-aspartate also give excellent fits to these models. However, there are some quantitative differences in the estimates of the compartment sizes and exchange constants, which are obtained by optimizing the fit of the data to the equation for each model. Although most of these quantitative differences appear to be minor, one difference between the two studies is of potential significance in interpretation of the results. In the glutamate study, all depolarizing media were found to reduce the exchange constant for the carrier mechanism, while in the present study, depolarizing media were found to increase the exchange constant, with the exception of veratrine-containing medium without calcium.