Calcium messages in flagella are faster than messenger particles.

Calcium is one of the most versatile messengers for intracellular signaling. In the case of cilia and flagella calcium has the central role in transfer of communications between extracellular stimuli and intracellular formation of frequency modulated signal and their deciphering by target proteins. In this paper, the diffusion of fluorescently or otherwise tagged and un-tagged Ca2＋ particles is analyzed by solving the system of pertaining reaction-diffusion equations. We used Fourier transform tools to get asymptotic eigenfunctions for tagged (un-tagged) free and buffered Ca2＋ ions. We made some numerical estimations for diffusion coefficients corroborating the fact that messages diffuse faster than Ca2＋ messengers. From the best of our knowledge, this is the first time that Ca2＋ signaling in living cells is biophysically elaborated within the framework of model presented here. We suggest the experimental assay on the basis of radioactive Ca2＋ as tagged probe.

Effects of Grinding Methods and Water-to-Binder Ratio on the Properties of Cement Mortars Blended with Biomass Ash and Ceramic Powder.

To combat environmental challenges-such as the depletion of natural resources and a high carbon footprint-and contribute to the effort of achieving zero-waste technology and sustainable development, the use of agricultural and industrial wastes in the cement industry has created a research interest. This study explores the potential of two types of harvest residue ash (HRA) and three types of ceramic waste (CP) as supplementary cementitious materials (SCMs) through: (1) the characterization of raw materials and (2) examining the physical properties and mechanical performance of cement-based mortar samples prepared with 10%, 30% and 50%wt of the selected SCMs ground into powder form as cement replacement. Two main variables were the water-to-binder ratio (w/b) and the effect of different grinding procedures. Experimental results demonstrated that flexural and compressive strengths were not significantly impaired by SCM additions of up to 50%, but higher replacement levels led to an increased permeability and higher capillary water absorption due to the dilution effect. Also, a lower w/b was shown to effectively reduce the porosity of mortar and increase its mechanical properties, allowing for higher shares of SCMs to be utilized. This study verifies the technical feasibility of cob corn ash and ceramic powder application as SCMs in mortar formulations, further promoting the practice of incorporating industrial and agricultural by-products in greener cementitious composites.

Decoding the Bell-Shaped Calcium Spikes in Phosphorylation Cycles of Flagella.

We investigate the messenger role of calcium ions implicated in the regulation of wave-like bending dynamics of flagella. The emphasis is on microtubules of flagellar axoneme serving as nonlinear transmission lines for bell-shaped spikes of calcium ions. The calcium sensitive proteins, such as calmodulin, exhibit activation dependence on the spike train frequency and amplitude. Here, we analyze a Ca2+ decoding module IDA-I1 whose activity is controlled by Ca2+ activated kinase. We find that trains of Ca2+ spikes are advantageous compared to a constant rise in Ca2+ concentration as being more efficient and much less prone to noisy fluctuations.

Calcium ions tune the beats of cilia and flagella.

The cytoskeleton of cilia and flagella is so called axoneme a stable cylindrical architecture of nine microtubule doublets. Axoneme performs periodic bending motion by utilizing specific dynein motor family powered by ATP hydrolysis. It is still unclear how this highly organized "ciliary beat" is being initiated and strongly coordinated by the combined action of hundreds dynein motors. Based on the experimental evidences we here elaborate a plausible scenario in which actually calcium ions play the roles of catalytic activators and coordinators of dynein attachments doing it in superposition with already known mechanical control tools of "ciliary beat". Polyelectrolyte properties of microtubules incorporated in axoneme doublets enable the formation and propagation of soliton-like "ionic clouds" of Ca2+ ions along these "coaxial nanocables". The sliding speed of such Ca2+ "clouds" along microtubule doublets is comparable with the speed of propagation of "ciliary beat" itself. We elaborated the interplay between influx of Ca2+ ions in ciliary based body and the sliding of microtubule triplets therein. In second segment we considered how the dynein motors activated by Ca2+ ions contained within solitonic "ionic clouds" in competition with axoneme curvature regulate ciliary and flagellar beating.

How signals of calcium ions initiate the beats of cilia and flagella.

Cilia and flagella are cell organelles serving basic roles in cellular motility. Ciliary movement is performed by a sweeping-like repeated bending motion, which gives rise to a self-propagating "ciliary beat". The hallmark structure in cilia is the axoneme, a stable architecture of microtubule doublets. The motion of axoneme is powered by the axonemal dynein motor family powered by ATP hydrolysis. It is still unclear how the organized beat of cilium and flagella emerges from the combined action of hundreds of dynein molecules. It has been hypothesized that such coordination is mediated by mechanical stress due to transverse, radial or sliding deformations. The beating asymmetry is crucial for airway ciliary function and it requires tubulin glutamination a unique posttranslational modification of C-termini of constituent microtubules that is highly abundant in cilia and flagella. The exact role of tubulin glutamination in ciliary or flagellar function is still unclear. In this paper we analyze the role of calcium (Ca2+) ions based on the experimental evidence that the flagellar asymmetry can be increased due to the entry of extracellular Ca2+ through, for example, the nimodipine-sensitive pathway located in the flagella. We propose a new scenario based on the polyelectrolyte properties of cellular microtubules (MTs) such that dynamic influx of Ca2+ ions provides the initiation and synchronization of dynein sliding along microtubules. We also point out the possible interplay between tubulin polyglutaminated C-termini and localized pulses of Ca2+ ions along microtubules.

Metal contamination of short-term snow cover near urban crossroads: correlation analysis of metal content and fine particles distribution.

Snow samples were collected near crossroads in Novi Sad, Serbia, during December 2009 to assess metal concentrations (Ca, K, Zn, Fe, Cu, Mn, Al, Pb and Na), fine particle distribution and pH value. The filtered samples of melted snow were analysed, with a focus on particles smaller than a few µm. The most common values of the frequency number distribution curve were either in the range of 0.05-0.07 µm or one order of magnitude higher (0.2-0.5 µm). At examined locations metal concentrations varied from 0.0004 mg L(-1) for Pb to 18.9 mg L(-1) for Na. Besides Na, which mostly originated from de-icing salt, Ca is found to be the most abundant element in snow indicating the dominant influence of natural factors on snow chemistry. No significant difference was found in concentration of the elements at locations near crossroads with either low or high traffic volume, except for Na and Zn. To investigate how metals were related a correlation analysis was done for the concentrations of metals and with respect to the particle size distribution parameters and pH values. The major influence on the fine particle volume (mass) was concluded to be due to the elements from anthropogenic sources. This conclusion was based on the significant positive correlation between Fe, Zn and Al and the fine particle volume based distribution parameters.