A temporal and morphological framework for flower development in Antirrhinum majus

2004 ◽  
Vol 82 (5) ◽  
pp. 681-690 ◽  
Author(s):  
Coral A Vincent ◽  
Enrico S Coen
Keyword(s):  
Growth Rate ◽  
Flower Development ◽  
Time Course ◽  
Similar Rate ◽  
Antirrhinum Majus ◽  
Time Intervals ◽  
Regular Time ◽  
Constant Rate ◽  
Phases Of Development ◽  
Bud Morphology

The entire course of flower development in Antirrhinum majus L., from initiation to maturity, is described in terms of regular time intervals. Floral meristem and bud morphology was determined by scanning electron microscopy for a sequence of 58 plastochrons. These can be grouped to define 15 stages or 7 phases of development, providing a temporal framework for gene expression and key morphological events, such as the formation of the complex corolla. The time course is also used to estimate overall growth rates of sepals and petals. Sepals initially grow at a constant rate, but growth rate gradually declines at later stages and sepal growth eventually arrests before flower development is complete. Petals initially grow at a similar rate to that of early sepals, but this growth rate is maintained for a longer period, accounting for the larger size of mature petals relative to sepals. Comparisons with Arabidopsis indicate that the duration of growth also makes an important contribution to variation in flower size.Key words: Antirrhinum, flower development, meristems, zygomorphy, developmental timing, petal.

Interactive effect of inhaled bradykinin with histamine and PGD2 in bronchial asthma

1993 ◽  
Vol 75 (5) ◽  
pp. 1996-2002 ◽  
Author(s):  
K. Rajakulasingam ◽  
G. Gnanakumaran ◽  
M. K. Church ◽  
P. H. Howarth ◽  
S. T. Holgate
Keyword(s):  
Time Course ◽  
Interactive Effect ◽  
Forced Expiratory Volume ◽  
Time Intervals ◽  
Pharmacological Interaction ◽  
Regular Time ◽  
Airway Caliber ◽  
Rate Of Recovery ◽  
Time Courses ◽  
Pharmacologically Active

Interaction among mediators such as bradykinin (BK), histamine (H), and prostaglandin (PG) D2 may contribute to reduction in airway caliber in asthma. Ten stable asthmatic subjects took part in a study to investigate possible mediator interaction. The provocative concentration of mediator required to reduce forced expiratory volume in 1 s (FEV1) by 12.5% from the starting baseline value (PC12.5) and that required to reduce the fall in FEV1 from 12.5 to 25% (PC25–12.5) of H, BK, and PGD2 were determined. On three subsequent occasions, subjects inhaled either the vehicle plus BK PC12.5 or the vehicle plus H or PGD2 PC25–12.5, and FEV1 was measured at regular time intervals up to 40 min. Predicted time course curves were calculated from these results. On two additional occasions, interactive time course studies were undertaken when the subject inhaled BK PC12.5 followed by H or PGD2 PC25–12.5. On a further three visits, the time courses of individual mediators were studied. When BK was combined with H and PGD2, the maximum fall in FEV1 and the rate of recovery after inhalation of the second mediator were not significantly different from those values of predicted time course responses for the same combination of mediator. Thus, by employing pharmacologically active concentrations of inhaled BK, H, and PGD2, which act through separate receptor mechanisms, we were unable to demonstrate any pharmacological interaction on airway caliber in asthma.

Genetic variation in aspects of leaf growth of Populusclones, using the leaf plastochron index

1988 ◽  
Vol 18 (8) ◽  
pp. 1069-1077 ◽  
Author(s):  
R. Ceulemans ◽  
I. Impens ◽  
V. Steenackers
Keyword(s):  
Growth Rate ◽  
Production Rate ◽  
Growth Rates ◽  
Leaf Growth ◽  
Controlled Environment ◽  
Time Intervals ◽  
Leaf Production ◽  
Leaf Maturity ◽  
Regular Time ◽  
Plastochron Index

Leaf growth characteristics of seven clones of Populustrichocarpa, P. nigra, and interspecific hybrids with P. deltoides were examined on 1-year-old cuttings grown in a controlled-environment growth chamber. The plastochron index, a morphological time scale that is a linear function of time and correlated with other morphogenetic and physiological developmental processes, was applied to this development and growth study. Uniformity of leaf initiation was studied; new leaves were initiated at regular time intervals, at least under the controlled conditions of this study. Clones with a high leaf production rate (e.g., P. nigra clone Italica) had a low leaf growth rate and leaves reached maturity at a high leaf plastochron index (LPI 11). Fast-growing and high-yielding P. trichocarpa × P. deltoides hybrids showed the highest leaf growth rates and had a similar leaf production rate to P. trichocarpa. Despite considerable differences in leaf production rates, leaf maturity, and absolute leaf growth rates, only small differences in relative leaf growth rate were observed among the clones.

Functional Properties of p-Anisoylated Plasmin-Staphylokinase Complex

1993 ◽  
Vol 70 (02) ◽  
pp. 326-331 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
R A G Smith ◽  
D Collen
Keyword(s):  
Human Plasma ◽  
Rate Constant ◽  
Time Course ◽  
Bolus Injection ◽  
Similar Rate ◽  
Clot Lysis ◽  
Lag Phase ◽  
Plasma Clot ◽  
Rapid Clearance ◽  
Stoichiometric Complex

SummaryThe kinetic and fibrinolytic properties of a reversibly acylated stoichiometric complex between human plasmin and recombinant staphylokinase (plasmin-STAR complex) were evaluated. The acylation rate constant of plasmin-STAR by p-amidinophenyl-p’-anisate-HCI was 52 M-1 s-1 and its deacylation rate constant 1.2 × 10-4 s-1 (t½ of 95 min) which are respectively 50-fold and around 3-fold lower than for the plasmin-streptokinase complex. The acylated complex was stable as evidenced by binding to lysine-Sepharose. However, following an initial short lag phase, the acylated plasmin-STAR complex activated plasminogen at a similar rate as the unblocked complex, whereas the acylated plasmin-streptokinase complex did not activate plasminogen. These findings indicate that STAR, unlike streptokinase, dissociates from its acylated complex with plasmin in the presence of excess plasminogen. In agreement with this hypothesis, the time course of the lysis of a 125I-fibrin labeled plasma clot submerged in citrated human plasma, is similar for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR (50% clot lysis in 2 h requires 12 nM of each agent). The plasma clearances of STAR-related antigen following bolus injection in hamsters were 1.0 to 1.5 ml/min for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR, as a result of short initial half-lives of 2.0 to 2.5 min.The dissociation of the anisoylated plasmin-STAR complex and its consequent rapid clearance suggest that it has no apparent advantages as compared to free STAR for clinical thrombolysis.

scholarly journals Speech rhythm: a metaphor?

2014 ◽  
Vol 369 (1658) ◽  
pp. 20130396 ◽  
Author(s):  
Francis Nolan ◽  
Hae-Sung Jeon
Keyword(s):  
Traditional View ◽  
Time Intervals ◽  
Speech Rhythm ◽  
Linguistic Structure ◽  
Regular Time ◽  
Linguistic Functions ◽  
Absence Of Evidence ◽  
Metaphorical Extension ◽  
Analogical Process

Is speech rhythmic? In the absence of evidence for a traditional view that languages strive to coordinate either syllables or stress-feet with regular time intervals, we consider the alternative that languages exhibit contrastive rhythm subsisting merely in the alternation of stronger and weaker elements. This is initially plausible, particularly for languages with a steep ‘prominence gradient’, i.e. a large disparity between stronger and weaker elements; but we point out that alternation is poorly achieved even by a ‘stress-timed’ language such as English, and, historically, languages have conspicuously failed to adopt simple phonological remedies that would ensure alternation. Languages seem more concerned to allow ‘syntagmatic contrast’ between successive units and to use durational effects to support linguistic functions than to facilitate rhythm. Furthermore, some languages (e.g. Tamil, Korean) lack the lexical prominence which would most straightforwardly underpin prominence of alternation. We conclude that speech is not incontestibly rhythmic, and may even be antirhythmic. However, its linguistic structure and patterning allow the metaphorical extension of rhythm in varying degrees and in different ways depending on the language, and it is this analogical process which allows speech to be matched to external rhythms.

Processing and Excellent Oxidation Resistance of Nanocrystalline Fe-Cr Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 1122-1125
Author(s):  
Rajeev K. Gupta ◽  
B.V. Mahesh ◽  
R.K. Singh Raman ◽  
Carl C. Koch
Keyword(s):  
Oxidation Resistance ◽  
Secondary Ion Mass Spectrometry ◽  
Nanocrystalline Alloy ◽  
High Energy ◽  
Processing Route ◽  
Protective Oxide ◽  
Time Intervals ◽  
Regular Time ◽  
Order Of Magnitude ◽  
Energy Ball

Nanocrystalline and microcrystalline Fe-10Cr alloys were prepared by high energy ball milling followed by compaction and sintering, and then oxidized in air for 52 hours at 400°C. The oxidation resistance of nanocrystalline Fe-10Cr alloy as determined by measuring the weight gain after regular time intervals was compared with that of the microcrystalline alloy of same chemical composition (also prepared by the same processing route and oxidized under identical conditions). Oxidation resistance of nanocrystalline Fe10Cr alloy was found to be in excess of an order of magnitude superior than that of microcrystalline Fe10Cr alloy. The paper also presents results of secondary ion mass spectrometry of oxidized samples of nanocrystalline and microcrystalline Fe-Cr alloys, evidencing the formation of a more protective oxide scale in the nanocrystalline alloy.

Decomposition of Growth Curves into Growth Rate and Acceleration: a Novel Procedure to Monitor Bacterial Growth and the Time-Dependent Effect of Antimicrobials

2021 ◽  
Author(s):  
M. Luisa Navarro-Pérez ◽  
M. Coronada Fernández-Calderón ◽  
Virginia Vadillo-Rodríguez
Keyword(s):  
Growth Rate ◽  
Mathematical Models ◽  
Bacterial Growth ◽  
Time Course ◽  
Antimicrobial Agents ◽  
Numerical Procedure ◽  
Growth Curves ◽  
Predictive Microbiology ◽  
Insight Into ◽  
Over Time

In this paper, a simple numerical procedure is presented to monitor the growth of Streptococcus sanguinis over time in the absence and presence of propolis, a natural antimicrobial. In particular, it is shown that the real-time decomposition of growth curves obtained through optical density measurements into growth rate and acceleration can be a powerful tool to precisely assess a large range of key parameters [ i.e. lag time ( t 0 ), starting growth rate ( γ 0 ), initial acceleration of the growth ( a 0 ), maximum growth rate ( γ max ), maximum acceleration ( a max ) and deceleration ( a min ) of the growth and the total number of cells at the beginning of the saturation phase ( N s )] that can be readily used to fully describe growth over time. Consequently, the procedure presented provides precise data of the time course of the different growth phases and features, which is expected to be relevant, for instance, to thoroughly evaluate the effect of new antimicrobial agents. It further provides insight into predictive microbiology, likely having important implications to assumptions adopted in mathematical models to predict the progress of bacterial growth. Importance: The new and simple numerical procedure presented in this paper to analyze bacterial growth will possibly allow identifying true differences in efficacy among antimicrobial drugs for their applications in human health, food security, and environment, among others. It further provides insight into predictive microbiology, likely helping in the development of proper mathematical models to predict the course of bacterial growth under diverse circumstances.

Fast-phase transvascular fluid flux and the Fahraeus effect

1987 ◽  
Vol 62 (4) ◽  
pp. 1513-1520 ◽  
Author(s):  
W. N. Richardson ◽  
D. Bilan ◽  
M. Hoppensack ◽  
L. Oppenheimer
Keyword(s):  
Mechanical Properties ◽  
Slow Rate ◽  
Time Course ◽  
Rate Of Change ◽  
Distributed Model ◽  
Slow Phase ◽  
Fluid Flux ◽  
Fast Phase ◽  
Constant Rate ◽  
Fahraeus Effect

Transvascular fluid flux was induced in six isolated blood-perfused canine lobes by increasing and decreasing hydrostatic inflow pressure (Pi). Fluid flux was followed against the change in concentration of an impermeable tracer (Blue Dextran) measured directly with a colorimetric device. The time course of fluid flux was biphasic with an initial fast transient followed by a slow phase. Hematocrit changes unrelated to fluid flux occurred due to the Fahraeus effect, and their contribution to the total color signal was subtracted to determine the rate of fast fluid flux (Qf). Qf was related to Pi to derive fast-phase conductance (Kf). Slow-phase Kf was calculated from the constant rate of change of lobe weight. For a mean change in Pi of 7 cmH2O, 40% of the color signal was due to fluid flux. Fast- and slow-phase Kf's were 0.86 +/- 0.15 and 0.27 +/- 0.05 ml X min-1. cmH2O–1 X 100 g dry wt-1. The fast-phase Kf is smaller than that reported for plasma-perfused lobes. Possible explanations discussed are the nature of the perfusate, the mechanical properties of the interstitium, and the slow rate of rise of the driving pressure at the filtration site on the basis of a distributed model of pulmonary vascular compliance.

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 The Toxic Effect of Manganese on the Acetylcholinesterase Activity in Rat Brains

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Vahid Yousefi Babadi ◽  
Leila Sadeghi ◽  
Kobra Shirani ◽  
Ali Akbar Malekirad ◽  
Mohammad Rezaei
Keyword(s):  
Toxic Effect ◽  
Ache Activity ◽  
Time Course ◽  
Acetylcholinesterase Activity ◽  
Time Intervals ◽  
Chronic Dose ◽  
Essential Nutrient ◽  
Short Time ◽  
Chronic Doses ◽  
Dose Dependent

Manganese (Mn) is a naturally occurring element and an essential nutrient for humans and animals. However, exposure to high levels of Mn may cause neurotoxic effects. Accumulation of manganese damages central nervous system and causes Parkinson’s disease-like syndrome called manganism. Mn neurotoxicity has been suggested to involve an imbalance between the DAergic and cholinergic systems. The pathological mechanisms associated with Mn neurotoxicity are poorly understood, but several reports have established it is mediated by changing of AChE activity that resulted in oxidative stress. Therefore we focused the effect of Mn in AChE activity in the rat’s brain by MnCl2injection intraperitoneally and analyzed their brains after time intervals. This study used different acute doses in short time course and different chronic doses at different exposing time to investigate which of them (exposing dose or time) is more important in Mn toxic effect. Results showed toxic effect of Mn is highly dose dependent and AChE activity in presence of chronic dose in 8 weeks reaches acute dose in only 2 days.

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