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At least 649 records · Page 36Linked to original sources

PubMed2001

Ground performance of air conditioning and water recycle system for a Space Plant Box.

Researchers from 5 Japanese universities have developed a plant growth facility (Space Plant Box) for seed to seed experiments under microgravity. The breadboard model of the Space Plant Box was fabricated by assembling subsystems developed for microgravity. The subsystems include air conditioning and water recycle system, air circulation system, water and nutrient delivery system, lighting system and plant monitoring system. The air conditioning and water recycle system is simply composed of a single heat exchanger, two fans and hydrophilic fibrous strings. The strings allow water movement from the cooler fin in the Cooling Box to root supporting materials in the Plant Growth Chamber driven by water potential deficit. Relative humidity in the Plant Growth Chamber can be changed over a wide range by controlling the ratio of latent heat exchange to sensible heat exchange on the cooling fin of the heat exchanger. The transpiration rate was successfully measured by circulating air inside the Plant Growth Chamber only. Most water was recycled and a small amount of water needed to be added from the outside. The simple, air conditioning and water recycle system for the Space Plant Box showed good performance through a barley (Hordeum vulgare L.) growth experiment.

Air Conditioning↗

PubMed2002

Phase scaling properties of perturbation-induced multistability in a driven nonlinear system.

Phase scaling relations for the onsets of both saddle-node bifurcations and boundary crises induced by resonant periodic perturbations at subharmonic frequencies are found in a period-doubled system from the results of numerical simulation. These phase dependences determine the domains of existence of induced attractors in (bifurcation parameter, perturbation phase) parameter space. The overlapping of these domains leads to the formation of zones with different numbers of coexisting attractors. The numerical evidence was obtained on the basis of single-mode rate equations of a laser with parameters corresponding to a realistic loss-modulated CO2 laser.

Journal Article↗

PubMed2001

Transgene expression patterns indicate that spaceflight affects stress signal perception and transduction in arabidopsis.

The use of plants as integral components of life support systems remains a cornerstone of strategies for long-term human habitation of space and extraterrestrial colonization. Spaceflight experiments over the past few decades have refined the hardware required to grow plants in low-earth orbit and have illuminated fundamental issues regarding spaceflight effects on plant growth and development. Potential incipient hypoxia, resulting from the lack of convection-driven gas movement, has emerged as a possible major impact of microgravity. We developed transgenic Arabidopsis containing the alcohol dehydrogenase (Adh) gene promoter linked to the beta-glucuronidase (GUS) reporter gene to address specifically the possibility that spaceflight induces the plant hypoxia response and to assess whether any spaceflight response was similar to control terrestrial hypoxia-induced gene expression patterns. The staining patterns resulting from a 5-d mission on the orbiter Columbia during mission STS-93 indicate that the Adh/GUS reporter gene was activated in roots during the flight. However, the patterns of expression were not identical to terrestrial control inductions. Moreover, although terrestrial hypoxia induces Adh/GUS expression in the shoot apex, no apex staining was observed in the spaceflight plants. This indicates that either the normal hypoxia response signaling is impaired in spaceflight or that spaceflight inappropriately induces Adh/GUS activity for reasons other than hypoxia.

Alcohol Dehydrogenase↗

PubMed1996

Choline transport in rat liver basolateral plasma membrane vesicles.

Previous studies have demonstrated several pathways for the sinusoidal uptake of endogenous and exogenous organic cations, including two distinct organic cation:H+ exchanges and a separate carrier-mediated system driven by the inside-negative membrane potential. In this study, the driving force(s) for the uptake of the endogenous quaternary amine, choline, were determined in rat liver basolateral plasma membrane (blLPM) vesicles. Choline uptake into an osmotically sensitive space was not stimulated by an outwardly directed H+ or inwardly directed Na+ gradient. Instead, an inside-negative K+ diffusion potential stimulated choline uptake, suggesting the presence of a conductive pathway for choline uptake in bILPM vesicles. Conductive choline uptake was confirmed by inducing variable changes in the transmembrane potential with anions of different membrane permeability. Choline uptake in blLPM vesicles exhibitied 1) temperature dependency; 2) trans-stimulation; and 3) saturability, with an approximate Michaelis constant (Km) of 0.34 mmol/L and maximum velocity (Vmax) of 0.45 nmol/mg protein/15 s. Choline uptake in blLPM vesicles was cis-inhibited by the structurally similar derivative, hemicholinium-3 and acetylcholine, but not by substrates for other organic cation transport processes identified in blLPM vesicles, including thiamine, tetraethylammonium (TEA), tri-n-butyl-methylammonium (TBuMA), and N'-methylnicotinamide (NMN). These findings demonstrate an electrogenic pathway on the sinusoidal membrane for the uptake of this essential nutrient and support the existence of multiple pathways for the sinusoidal uptake of endogenous and exogenous organic cations.

Animals↗

PubMed2006

Cytokinesis in plant and animal cells: endosomes 'shut the door'.

For many years, cytokinesis in eukaryotic cells was considered to be a process that took a variety of forms. This is rather surprising in the face of an apparently conservative mitosis. Animal cytokinesis was described as a process based on an actomyosin-based contractile ring, assembling, and acting at the cell periphery. In contrast, cytokinesis of plant cells was viewed as the centrifugal generation of a new cell wall by fusion of Golgi apparatus-derived vesicles. However, recent advances in animal and plant cell biology have revealed that many features formerly considered as plant-specific are, in fact, valid also for cytokinetic animal cells. For example, vesicular trafficking has turned out to be important not only for plant but also for animal cytokinesis. Moreover, the terminal phase of animal cytokinesis based on midbody microtubule activity resembles plant cytokinesis in that interdigitating microtubules play a decisive role in the recruitment of cytokinetic vesicles and directing them towards the cytokinetic spaces which need to be plugged by fusing endosomes. Presently, we are approaching another turning point which brings cytokinesis in plant and animal cells even closer. As an unexpected twist, new studies reveal that both plant and animal cytokinesis is driven not so much by Golgi-derived vesicles but rather by homotypically and heterotypically fusing endosomes. These are generated from cytokinetic cortical sites defined by preprophase microtubules and contractile actomyosin ring, which induce local endocytosis of both the plasma membrane and cell wall material. Finally, plant and animal cytokinesis meet together at the physical separation of daughter cells despite obvious differences in their preparatory events.

Actomyosin↗

PubMed1996

Past and future of computer-assisted sleep analysis and drowsiness assessment.

The development of computerized sleep analysis has been very much technology-driven by both mathematical tools and available hardware but, additionally and unfortunately, by the almost-30-year-old standard used for manual sleep stage scoring of paper recordings. There are no technical restrictions in terms of computing power, storage space, and costs anymore. However, the standards of visual sleep stage scoring have proven insufficient and ambiguous, and their utilization evidently provides misleading and erroneous information. The low temporal resolution provided by the one-page epoch, the crude division of the sleep processes into a few discrete stages, and the total ignorance of spatial information are the major drawbacks. It is meaningless to try to improve the computerised systems if the algorithms are based on erroneous concepts. Instead, the focus should be changed to studies dealing with the identification and modelling of true biological sleep-related processes. This work cannot be performed without the successful application of computerized methods, some of which have been used in related fields but have not yet been applied to sleep studies. It is extremely important that basic findings are confirmed with a wide variety of methods in several laboratories. The use of predetermined, fixed criteria for methods, waveforms, and states too early is scientifically erroneous and hazardous. Instead standards should describe the minimum requirements for the recording and analysis of the signals in terms of sampling rate, dynamic range, linearity, and documentation of the methods used. With the development of better technology, these standards ought to be constantly reevaluated and modified. The development toward more open commercial digital systems, including standardized programming methods and data formats, would have great positive impact to the field. These trends have long been established in many other fields of industry.

Algorithms↗

PubMed2002

Subharmonic stochastic synchronization and resonance in neuronal systems.

We study the response of a model neuron, driven simultaneously by noise and at least two weak periodic signals. We focus on signals with frequencies components kf(0),(k+1)f(0),...(k+n)f(0) with k>1. The neuron's output is a sequence of pulses spaced at random interpulse intervals. We find an optimum input noise intensity for which the output pulses are spaced approximately 1/f(0), i.e., there is a stochastic resonance (SR) at a frequency missing in the input. Even higher noise intensities uncover additional, but weaker, resonances at frequencies present in the input. This is a different form of SR whereby the most robust resonance is the one enhancing a frequency, which is absent in the input, and which is not possible to recover via any linear processing. This can be important in understanding sensory systems including the neuronal mechanism for perception of complex tones.

Algorithms↗

PubMed2005

Signatures of chaoticlike and nonchaoticlike behavior in a nonlinear quantum oscillator through photon detection.

The driven nonlinear Duffing oscillator is a very good, and standard, example of a quantum mechanical system from which classical-like orbits can be recovered from unravelings of the master equation. In order to generate such trajectories in the phase space of this oscillator, in this paper we use the quantum jump unraveling together with a suitable application of the correspondence principle. We analyze the measured readout by considering the power spectra of photon counts produced by the quantum jumps. Here we show that localization of the wave packet from the measurement of the oscillator by the photon detector produces a concomitant structure in the power spectra of the measured output. Furthermore, we demonstrate that this spectral analysis can be used to distinguish between different modes of the underlying dynamics of the oscillator.

Journal Article↗

PubMed2006

Escape rate from a metastable state weakly interacting with a heat bath driven by external noise.

Based on a system-reservoir model, where the reservoir is driven by an external stationary, Gaussian noise with arbitrary decaying correlation function, we study the escape rate from a metastable state in the energy diffusion regime. For the open system we derive the Fokker-Planck equation in the energy space and subsequently calculate the generalized non-Markovian escape rate from a metastable well in the energy diffusion domain. By considering the dynamics in a model cubic potential we show that the results obtained from numerical simulation are in good agreement with the theoretical prediction. It has been also shown numerically that the well-known turnover feature can be restored from our model.

Colloids↗

PubMed2005

Laser-induced fluorescence measurement of the ion-energy-distribution function in a collisionless reconnection experiment.

Observations in space and laboratory plasmas suggest magnetic reconnection as a mechanism for ion heating and formation of non-Maxwellian ion velocity distribution functions (IVDF). Laser-induced fluorescence measurements of the IVDF parallel to the X line of a periodically driven reconnection experiment are presented. A time-resolved analysis yields the evolution of the IVDF within a reconnection cycle. It is shown that reconnection causes a strong increase of the ion temperature, where the strongest increase is found at the maximum reconnection rate. Monte Carlo simulations demonstrate that ion heating is a consequence of the in-plane electric field that forms around the X line in response to reconnection.

Journal Article↗

PubMed2005

Motif extraction and protein classification.

We present a novel unsupervised method for extracting meaningful motifs from biological sequence data. This de novo motif extraction (MEX) algorithm is data driven, finding motifs that are not necessarily over-represented in the data. Applying MEX to the oxidoreductases class of enzymes, containing approximately 7000 enzyme sequences, a relatively small set of motifs is obtained. This set spans a motif-space that is used for functional classification of the enzymes by an SVM classifier. The classification based on MEX motifs surpasses that of two other SVM based methods: SVMProt, a method based on the analysis of physical-chemical properties of a protein generated from its sequence of amino acids, and SVM applied to a Smith-Waterman distances matrix. Our findings demonstrate that the MEX algorithm extracts relevant motifs, supporting a successful sequence-to-function classification.

Algorithms↗

PubMed1994

Characterization of cis-regulating elements and trans-activating factors of the rat cardiac troponin T gene.

To study the transcriptional regulation of the rat cardiac troponin T (cTnT) gene, chimeric genes composed of the upstream region (-757 to +193 base pairs (bp) relative to the transcription initiation site) of the cTnT gene and the bacterial chloramphenicol acetyltransferase (CAT) gene were constructed and transfected into primary cultures of neonatal cardiomyocytes and cardiac fibroblasts. Deletion analysis showed that a 41-bp fragment (-249 to -209 bp) containing the MEF-2-like motif is an essential element for minimal cardiac-specific expression of the rat cTnT gene. The proximal promoter (-208 to -1 bp) contains two consensus CArG boxes, one M-CAT motif, one AP2 site, and one TATA box. The construct (cTNT-208) composed of the CAT reporter gene driven by this proximal promoter did not show cardiac muscle-specific expression. Ligation of consensus MEF-2-like sequence into the upstream of this chimera only partially increased its ability to express in cardiomyocytes. These results suggest that the spacing among MEF-2-like motif and proximal promoter and/or the flanking sequences of the MEF-2-like motif are important in determining cardiac muscle-specific expression. By footprint analysis with a DNA fragment (-303 to +6 bp), we identified three novel regions (called A, B, and C) protected by protein extract from rat hearts, in addition to the known motifs such as MEF-2, M-CAT, and CArG. Gel retardation with the probe (-235 to -141 bp), containing the MEF-2-like motif, one of the CArG boxes, and the C region, or the 41-bp probe (-249 to -209 bp), containing the MEF-2-like motif, revealed different DNA-protein complexes formed by heart, skeletal muscle, and liver extracts. By using DNA affinity purification, DNA-binding proteins with apparent molecular masses of 22-26 kDa were identified from rat heart extract but not from skeletal and liver extracts, suggesting the involvement of cardiac-specific proteins in regulating the cTnT gene expression.

Animals↗

PubMed1994

ATP-dependent transport of tetraethylammonium by endosomes isolated from rat renal cortex.

During renal organic cation secretion by some species, intracellular concentrations greatly exceed the 10- to 15-fold ratio predicted by the potential-driven mechanism thought to mediate their basolateral uptake. Free cytoplasmic organic cation concentrations within the tubular cells might be decreased through sequestration within intracellular organelles. The data reported here show that endosomal vesicles isolated from rat renal cortex take up tetraethylammonium (TEA) by an ATP-dependent mechanism. Addition of 0.2-5 mM ATP to the medium stimulated uptake 5- to 10-fold at 5 min and 20-fold at 60 min. More than 80% of the ATP-dependent uptake was associated with an osmotically active space. The nonhydrolyzable ATP analogue, adenosine 5'-O-(3-thiotriphosphate), did not stimulate TEA uptake. Mg2+ and Cl- were required for stimulation. Uptake was inhibited by several organic cations, including TEA itself. Uptake was also inhibited by inhibitors of intravesicular acidification, e.g., monensin and N-ethylmaleimide. Furthermore, the ATP requirement could be bypassed by establishing a pH gradient (inside acidic). These data show that endosomal TEA accumulation is mediated by proton/TEA exchange and is driven by the pH gradient maintained by H(+)-adenosinetriphosphatase. This potent sequestration mechanism may play an important role in organic cation secretion.

Adenosine Triphosphate↗

PubMed2001

Inductance plethysmography: an alternative signal to servocontrol the airway pressure during proportional assist ventilation in small animals.

During proportional assist ventilation (PAV), the ventilator pressure is servocontrolled throughout each spontaneous inspiration such that it instantaneously increases in proportion to the airflow (resistive unloading mode), or inspired volume (elastic unloading mode), or both (combined unloading mode). The PAV pressure changes are generated in a closed-loop feedback circuitry commonly using a pneumotachographic signal. In neonates, however, a pneumotachograph increases dead space ventilation, and its signal may include a substantial endotracheal tube leak component. We hypothesized that respiratory inductive plethysmography (RIP) can replace pneumotachography to drive the ventilator during PAV without untoward effects on ventilation or respiratory gas exchange. Ten piglets and five rabbits were supported for 10-min (normal lungs) or 20-min (meconium injured lungs) periods by each of the three PAV modes. In each mode, three test periods were applied in random order with the ventilator driven by the pneumotachograph signal, or the RIP abdominal band signal, or the RIP sum signal of rib cage and abdomen. Interchanging the three input signals did not affect the regularity of spontaneous breathing, and gas exchange was achieved with similar peak and mean airway pressures (ANOVA). However, the RIP sum signal worked adequately only when the relative gains of rib cage and abdominal band signal were calibrated. We conclude that an RIP abdominal band signal can be used to generate PAV, avoiding increased dead space and endotracheal tube leak problems.

Airway Resistance↗

PubMed2006

A novel synthetic mammalian promoter derived from an internal ribosome entry site.

Introduction of specific mutations into a synthetic internal ribosome entry site (IRES(GTX)) derived from the GTX homeodomain protein revealed additional transcriptional activity. This novel synthetic P(GTX) promoter exhibited consensus core promoter modules such as the initiator (Inr) and the partial downstream promoter elements (DPE) and mediated high-level expression of a variety of transgenes including the human vascular endothelial growth factor 121 (VEGF(121)), the human placental secreted alkaline phosphatase (SEAP), and the Bacillus stearothermophilus-derived secreted alpha-amylase (SAMY) in Chinese hamster ovary cells (CHO-K1) and a variety of other mammalian and human cell lines. The spacing between Inr and DPE modules was found to be critical for promoter performance since introduction of a single nucleotide (resulting in P(GTX2)) doubled the SEAP expression levels in CHO-K1. P(GTX2) reached near 70% of P(SV40)-driven expression levels and outperformed constitutive phosphoglycerate kinase (P(PGK)) and human ubiquitin C (P(hUBC)) promoters in CHO-K1. Also, P(GTX2) was successfully engineered for macrolide-inducible transgene expression. Owing to its size of only 182 bp, P(GTX2) is one of the smallest eukaryotic promoters. Although P(GTX2) was found to be a potent promoter, it retained its IRES(GTX)-specific translation-initiation capacity. Synthetic DNAs, which combine multiple activities in a most compact sequence format may foster advances in therapeutic engineering of mammalian cells.

Animals↗

PubMed2006

Structures that contribute to middle-ear admittance in chinchilla.

We describe measurements of middle-ear input admittance in chinchillas (Chinchilla lanigera) before and after various manipulations that define the contributions of different middle-ear components to function. The chinchilla's middle-ear air spaces have a large effect on the low-frequency compliance of the middle ear, and removing the influences of these spaces reveals a highly admittant tympanic membrane and ossicular chain. Measurements of the admittance of the air spaces reveal that the high-degree of segmentation of these spaces has only a small effect on the admittance. Draining the cochlea further increases the middle-ear admittance at low frequencies and removes a low-frequency (less than 300 Hz) level dependence in the admittance. Spontaneous or sound-driven contractions of the middle-ear muscles in deeply anesthetized animals were associated with significant changes in middle-ear admittance.

Acoustic Impedance Tests↗

PubMed1994

Object-oriented model-driven control.

A monitoring and control subsystem architecture has been developed that capitalizes on the use of model-driven monitoring and predictive control, knowledge-based data representation, and artificial reasoning in an operator support mode. We have developed an object-oriented model of a Controlled Ecological Life Support System (CELSS). The model, based on the NASA Kennedy Space Center CELSS breadboard data, tracks carbon, hydrogen, and oxygen, carbon dioxide, and water. It estimates and tracks resource-related parameters such as mass, energy, and manpower measurements such as growing area required for balance. We are developing an interface with the breadboard systems that is compatible with artificial reasoning. Initial work is being done on use of expert systems and user interface development. This paper presents our approach to defining universally applicable CELSS monitor and control issues, and implementing appropriate monitor and control capability for a particular instance: the KSC CELSS Breadboard Facility.

Animals↗

PubMed2026

Identification of tomato leaf miner secretory proteins and their roles in influencing plant defenses.

The tomato leaf miner (Tuta absoluta) is a globally destructive pest that cause extensive damage to tomato crops by chewing mouthparts, leading to severe necrosis, fruit abortion, and substantial yield losses. To date, the elicitors/effectors of T. absoluta have not been characterized. In this study, we combined proteomic profiling of T. absoluta-infested tomato leaves with transcriptomic analysis of salivary glands to identify candidate molecules involved in herbivory-driven plant responses. Bioinformatics analyses predicted 40 candidate elicitors and effectors, which were subsequently assessed through transient expression assays in Nicotiana benthamiana. The results demonstrated that the candidate number 33 (T. absoluta 33, Ta33) induced cell death in both the intracellular space and the apoplast, while Ta21 triggered a strong apoplastic reactive oxygen species (ROS) burst. Conversely, Ta38 effectively suppressed INF1-induced cell death. Quantitative real-time PCR analysis further showed that these genes were highly expressed during the feeding stage, supporting their involvement in plant-insect molecular dialogue. This study systematically identified and characterized elicitors and effectors of T. absoluta, providing a foundational framework for elucidating its herbivory mechanisms and developing targeted management strategies.

Moths↗