Initial growth processes in seeds in magnetic fields,strengthened or weakened in relation to the geomagnetic field

The effects of modifications of magnetic fields, simulating anomalies of natural magnetism of the Earth, were studied in the seeds of peas and winter wheat. It has been shown that strengthening or weakening of the geomagnetic field inhibits water absorption and initial growth processes. The influence of magnetic fields on the orientation of rootlets and development of plantlets is determined. The connection between the magnetic susceptibility of seeds and content of heavy metals in them is established, which obviously concerns the magnetic susceptibility and magnetotropism in plants.     

Magnetic susceptibility of iron in malaria-infected red blood cells

During intra-erythrocytic maturation, malaria parasites catabolize up to 80% of cellular haemoglobin. Haem is liberated inside the parasite and converted to haemozoin, preventing haem iron from participating in cell-damaging reactions. Several experimental techniques exploit the relatively large paramagnetic susceptibility of malaria-infected cells as a means of sorting cells or investigating haemoglobin degradation, but the source of the dramatic increase in cellular magnetic susceptibility during parasite growth has not been unequivocally determined. Plasmodium falciparum cultures were enriched using high-gradient magnetic fractionation columns and the magnetic susceptibility of cell contents was directly measured. The forms of haem iron in the erythrocytes were quantified spectroscopically. In the 3D7 laboratory strain, the parasites converted approximately 60% of host cell haemoglobin to haemozoin and this product was the primary source of the increase in cell magnetic susceptibility. Haemozoin iron was found to have a magnetic susceptibility of (11.0 ± 0.9) × 10^? 3 mL mol^? 1. The calculated volumetric magnetic susceptibility (SI units) of the magnetically enriched cells was (1.88 ± 0.60) × 10^? 6 relative to water while that of uninfected cells was not significantly different from water. Magnetic enrichment of parasitised cells can therefore be considered dependent primarily on the magnetic susceptibility of the parasitised cells.     

Magnetophoresis and magnetic susceptibility of HeLa tumor cells

A method for measuring the magnetic susceptibility of separate cells has been theoretically developed and implemented in experiments. It is based on fitting the videocomputer and predicted data for the integral motion curve of cells that settle in a fluid along a thin ferromagnetic bar by the action of a uniform magnetic field. The magnetic susceptibility of HeLa tumor cells and culture medium 199 has been measured.     

A first-principles bottom-up study of the magnetic interaction mechanism in the bulk ferromagnet p-O2N-C6F4-CNSSN

The crystals of the p-nitro perfluorophenyl dithiadiazolyl radical have been shown to present bulk ferromagnetism below 1.32 K. Using our first-principles bottom-up methodology, the mechanism of the magnetic interactions in these crystals has been studied to gain a rigorous quantitative understanding of such bulk ferromagnetism. The p-O₂N-C₆F₄-CNSSN crystal is found to present only two non-negligible interactions (J(d1) = 0.83 cm^?1 and J(d3) = 0.07 cm^?1). The dominant interaction J(d1) generates a three-dimensional (3D) magnetic topology that can be described as a distorted diamond-like arrangement. Using the appropriate minimal magnetic model to describe this topology, the magnetic susceptibility and heat capacity curves were computed. A good agreement is found between the computed and experimental magnetic susceptibility data. Furthermore, the critical temperature obtained from the heat capacity curve (0.6 K) agrees well with the experimental one. A comparison of the magnetic data for p-O₂N-C₆F₄-CNSSN and four nitronyl nitroxide bulk ferromagnets indicates that the critical temperature not only depends on the size of the largest J interactions, but also on the corresponding magnetic topology.     

Magnetic parameters of the bees Apis mellifera mellifera (L.) obtained by SQUID-magnetometry

It was found using SQUID-magnetometry that the dependence of the magnetization of a bee on the intensity of the applied magnetic fields has the form of a hysteresis loop. By using the parameters of the loop, the magnetic phases were identified and their characteristics were determined. It was found that the diamagnetic component is significant and has a susceptibility = -1,3335 x 10(-8) Gs x cm3/Oe. The ferromagnetite phase is represented by a multidomain magnetite with the coercive force of 70-80 Oe and magnetic saturation momnts of 4 x 10(-5) EMU (Gs x cm3) and residual moment of 3.07 x 10(-6) EMU.     

Magneto‐optical characteristics of human sperms: normal and deformed

In this study we report on magnetic orientation of human sperms. Samples were taken from 17 donors. Normal human sperms became oriented with their long axis perpendicular to the magnetic field (1 T maximum). Total orientation was achieved with magnetic field of about 1 T, while for abnormal sperms the magnetic behavior was different. The dependence of the measured degree of orientation on the intensity of the magnetic field was in good agreement with the theoretical equation for the magnetic orientation of diamagnetic substances. As a result of a numerical analysis based on the equation, the anisotropic diamagnetic susceptibility of normal sperm was found to be Δ_χ = 8 × 10^–20 J/T². The degree of orientation was influenced by the alterations in the shape of the head, body or the tail. It has been suggested that the DNA in the sperm head retain the strong magnetic anisotropy to counterbalance the magnetic anisotropy retained by flagellum microtubules. Recent studies demonstrated a well‐defined nuclear architecture in human sperm nucleus, where the head morphology has significant correlation with sperm chromatin structure assay SCSA. Then, as the methods to evaluate SCSA can be difficult and expensive our simple magnetic orientation technique can be an alternative to diagnose alteration in DNA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bacterial cell biology: managing magnetosomes

Sensing of magnetic fields by living organisms -- magnetosensing -- is best understood in magnetotactic bacteria. Recently work has provided new insight into the biogenesis of bacterial magnetosomes, and links these organelles to a newly recognized prokaryotic cytoskeletal filament which organizes magnetosomes into a sensory structure capable of aligning cells with the geomagnetic field.     

Magnetic field-induced increase of the yield of (bacterio)chlorophyll emission of some photosynthetic bacteria and of Chlorella vulgaris.

In photosynthetic bacteria, in which the iron-ubiquinone complex X is prereduced, a magnetic field induces an increase of the emmission yield, which is correlated with the decrease in reaction center triplet yield reported previously (Hoff, A.J., Rademaker, H., van Grondelle, R. and Duysens, L.N.M. (1977) Biochim. Biophys. Acta 460, 547--554). Our results support the hypothesis that under these conditions charge recombination of the oxidized primary donor and the reduced primary acceptor predominantly generates the excited singlet state of the reaction center bacteriochlorophyll. In Chlorella vulgaris and spinach chloroplasts, at 120 K, the magnetic field has an effect similar to that found in bacteria, which suggests that an intermediary electron acceptor between P-680 and Q is present in Photosystem II also.     

The magnetic susceptibilities of iron deposits in thalassaemic spleen tissue

The iron-specific magnetic susceptibility of tissue iron deposits is used in the field of non-invasive measurement of tissue iron concentrations. It has generally been assumed to be a constant for all tissue and disease types. The iron-specific magnetic susceptibilities chi(Fe) for spleen tissue samples from 7 transfusion dependent beta-thalassaemia (beta-thal) patients and 11 non-transfusion dependent beta-thalassaemia/Haemoglobin E (beta/E) patients were measured at 37 degrees C. Both groups of patients were iron loaded with no significant difference in the distribution of spleen iron concentrations between the two groups. There was a significant difference between the mean chi(Fe) of the spleen tissue from each group. The non-transfusion dependent beta/E patients had a higher mean (+/-standard deviation) spleen chi(Fe) (1.55+/-0.23 x 10(-6) m(3)/kg Fe) than the transfusion dependent beta-thal patients (1.16+/-0.25 x 10(-6) m(3)/kg Fe). Correlations were observed between chi(Fe) of the spleen tissue and the fraction of magnetic hyperfine split sextet in the (57)Fe M?ssbauer spectra of the tissues at 78 K (Spearman rank order correlation r=-0.54, p=0.03) and between chi(Fe) of the spleen tissue and the fraction of doublet in the spectra at 5 K (r=0.58, p=0.02) indicating that chi(Fe) of the spleen tissue is related to the chemical speciation of the iron deposits in the tissue.     

Discovery of potent anti-tuberculosis agents targeting leucyl-tRNA synthetase

Tuberculosis is a serious infectious disease caused by human pathogen bacteria Mycobacterium tuberculosis. Bacterial drug resistance is a very significant medical problem nowadays and development of novel antibiotics with different mechanisms of action is an important goal of modern medical science. Leucyl-tRNA synthetase (LeuRS) has been recently clinically validated as antimicrobial target. Here we report the discovery of small-molecule inhibitors of M. tuberculosis LeuRS. Using receptor-based virtual screening we have identified six inhibitors of M. tuberculosis LeuRS from two different chemical classes. The most active compound 4-{[4-(4-Bromo-phenyl)-thiazol-2-yl]hydrazonomethyl}-2-methoxy-6-nitro-phenol (1) inhibits LeuRS with IC₅₀ of 6 μM. A series of derivatives has been synthesized and evaluated in vitro toward M. tuberculosis LeuRS. It was revealed that the most active compound 2,6-Dibromo-4-{[4-(4-nitro-phenyl)-thiazol-2-yl]-hydrazonomethyl}-phenol inhibits LeuRS with IC₅₀ of 2.27 μM. All active compounds were tested for antimicrobial effect against M. tuberculosis H37Rv. The compound 1 seems to have the best cell permeability and inhibits growth of pathogenic bacteria with IC₅₀ = 10.01 μM and IC₉₀ = 13.53 μM.     

Effect of fenibut on the GABA B receptors of the spinal motor neurons

It has been established in experiments on the isolated spinal cord of 7-14-day-old rats that the GABAB-mimetic phenibut (10(-5)--10(-4) M) elicits a slow-developing depolarization of motoneurons, suppression of spontaneous activity and polysynaptic reflex discharges of motoneurons, recorded from the ventral roots. Administered under the same conditions GABA produces de- and hyperpolarization of motoneurons. The depolarization of motoneurons elicited by phenibut and GABA is not reversed by picrotoxin in contradistinction to the GABA-induced hyperpolarization of motoneurons, being associated with a direct action of the GABA-mimetics on postsynaptic GABAB receptors of motoneurons. Diazepam (10(-9)--10(-6) M) potentiates the effects of phenibut supposedly via benzodiazepine receptors bound with GABAA receptors (an independent interaction).     

Quantification of magnetic susceptibility in several strains of Bacillus spores: implications for separation and detection

Three strains of Bacillus: Bacillus atrophaeus (formally Bacillus globigii), Bacillus thuringiensis, and Bacillus cereus were tested for their intrinsic magnetic susceptibility. All three strains when sporulated demonstrated significant magnetic susceptibility using an instrument referred to as Cell Tracking Velocimetry. Energy dispersive spectroscopy also confirmed the presence of paramagnetic elements, Fe and Mn, in the spore form of the bacteria. It was demonstrated that this magnetic susceptibility is sufficient to separate and deposit these spores on glass slides in a magnetic deposition system. These results indicate the potential to separate spores with intrinsic magnetic susceptibility directly out of water or air samples.     

东天山地区庙儿沟雪坑中微生物多样性、群落结构与环境关系研究

通过荧光计数、恢复培养和变形梯度凝胶电泳(DGGE),分析了东天山地区庙儿沟不同深度积雪中的可培养细菌数量、多样性及其群落结构。结果表明,东天山地区冰雪微生物数量和多样性指数与气候环境替代指标钙离子、镁离子、氯离子等具有相关性。该地区雪坑中细菌隶属于4个不同系统发育群:proteobacteria(α-,β-,γ-),CFB,HGC和LGC,其中CFB类和proteobacteria类为主要类群。与青藏高原、南北极冰雪中微生物的比较分析发现Paracoccu和Aquasalina属是该地区的特殊微生物类群。直接培养和DGGE分析发现不同深度雪坑中微生物数量和群落结构都有明显的变化。结果表明,由于东天山地区的特殊地理位置,该地区冰雪微生物具有其特殊性。     

Theoretical analysis of an iron mineral-based magnetoreceptor model in birds

Sensing the magnetic field has been established as an essential part of navigation and orientation of various animals for many years. Only recently has the first detailed receptor concept for magnetoreception been published based on histological and physical results. The considered mechanism involves two types of iron minerals (magnetite and maghemite) that were found in subcellular compartments within sensory dendrites of the upper beak of several bird species. But so far a quantitative evaluation of the proposed receptor is missing. In this article, we develop a theoretical model to quantitatively and qualitatively describe the magnetic field effects among particles containing iron minerals. The analysis of forces acting between these subcellular compartments shows a particular dependence on the orientation of the external magnetic field. The iron minerals in the beak are found in the form of crystalline maghemite platelets and assemblies of magnetite nanoparticles. We demonstrate that the pull or push to the magnetite assemblies, which are connected to the cell membrane, may reach a value of 0.2 pN -- sufficient to excite specific mechanoreceptive membrane channels in the nerve cell. The theoretical analysis of the assumed magnetoreceptor system in the avian beak skin clearly shows that it might indeed be a sensitive biological magnetometer providing an essential part of the magnetic map for navigation.     

Development of arterial and lymphatic collaterals under the action of a UHF magnetic field]

The work performed in 48 experimental and 24 control rats dealt with the development of arterial and lymphatic collaterals of pelvic extremities under effects of magnetic field of ultra high frequency (15 and 30 vt) in terms from 2 up to 6 weeks after surgery and exposure to magnetic field. The methods of investigation were arterio- and lymphoroentgenography and dissection. It has been established that formation of arterial collaterals in experimental rats takes place in all zones during the second week after cutting femoral arteries. The rate of the development of arterial collaterals was accelerated as compared with control animals. The lymph outflow after exposure to the influence of magnetic field of UHF goes mainly along superficial collaterals to groin nodes. The influence of the magnetic field of UHF appears to be accompanied by stable dilatation of super ficial lymph vessels, and due to this the lymph outflows along these vessels.     

Translation mobility of water isolated in the cells of lyophilized Cryptococcus albidus var. diffluens yeasts by the NMR impulse method

The method of NMR spin echo in a combination with the impulse gradient of the magnetic field was used to study the self-diffusion of water isolated in the cells of lyophylized Criptococcus. A relative fall of the amplitude of spin echo (factor R) in relation to the value of magnetic field impulse gradient (g), their duration (delta) and temporary distance between them (delta). The studies were carried out in the temperature range of 20 degrees divided by 80 degrees C. It has been shown that the fraction of isolated mobile water is located in intracellular permeable compartments with an average size of 0.6.10--4 cm at 20 degrees C. The coefficient of selfdiffusion of isolated water of Criptococcus (0.25.10--5 cm2S--1 at 20 degrees C) and the activation energy of selfdiffusion (4.4 ccal/mole at 20 degrees divided by 60 degrees C) were determined, permeability of walls of water-containing compartments taken into account.     

Effect of inoculation on nitrogen fixation by chick pea, on its crop and protein content]

Active strains of Rh. cicer were found to increase the crop of chick pea by 25--36%, the content of protein by 2--6%, and the content of total nitrogen in the roots by 1.7--2%. Symbiotic fixation of nitrogen determined by a technique of "inoculation" varies within 40--60% depending on the activity of the strain. No correlation has been established between the effectiveness of the strains of nodule bacteria and the activity of their enzymes--dehydrogenases.     

Synthesis, spectroscopic characterization and biological activity on newly synthesized copper(II) and nickel(II) complexes incorporating bidentate oxygen-nitrogen hydrazone ligands

We report the synthesis of the hydrazone ligands, 1-(phenyl-hydrazono)-propan-2-one (PHP), 1-(p-tolyl-hydrazono)-propan-2-one (THP), 1-[(4-chloro-hydrazono)]-propan-2-one (CHP), and their Ni(II) and Cu(II) metal complexes. The structure of the ligands and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, UV, and EPR) measurements. IR spectra indicate that the free ligands exist in the hydrazo-ketone rather than azo-enol form in the solid state. Also, the hydrazo-NH exists as hydrogen bonded to the keto-oxygen either as intra or as intermolecular hydrogen bonding. In all the studied complexes, all ligands behave as a neutral bidentate ligands with coordination involving the hydrazone-nitrogen and the keto-oxygen atoms. The magnetic and spectral data indicate a square planar geometry for Cu²⁺ complexes and an octahedral geometry for Ni²⁺ complexes. The ligands and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. It may be concluded that the antimicrobial activity of the compounds is related to cell wall structure of bacteria.Protonation constant of (PHP) ligand and stability constants of its Cu²⁺ and Ni²⁺ complexes were determined by potentiometric titration method in aqueous solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the hydrazone ligand (PHP) titrated here has one protonation constant. The divalent metal ions Cu²⁺ and Ni²⁺ form with (PHP) 1:1 and 1:2 complexes. The insolubility of (THP) and (CHP) ligands in aqueous medium does not permit the determination of their protonation constants and formation constants of the corresponding complexes in aqueous solution.     

Red blood cell magnetophoresis

The existence of unpaired electrons in the four heme groups of deoxy and methemoglobin (metHb) gives these species paramagnetic properties as contrasted to the diamagnetic character of oxyhemoglobin. Based on the measured magnetic moments of hemoglobin and its compounds, and on the relatively high hemoglobin concentration of human erythrocytes, we hypothesized that differential migration of these cells was possible if exposed to a high magnetic field. With the development of a new technology, cell tracking velocimetry, we were able to measure the migration velocity of deoxygenated and metHb-containing erythrocytes, exposed to a mean magnetic field of 1.40 T and a mean gradient of 0.131 T/mm, in a process we call cell magnetophoresis. Our results show a similar magnetophoretic mobility of 3.86 x 10(-6) mm(3) s/kg for erythrocytes with 100% deoxygenated hemoglobin and 3.66 x 10(-6) mm(3) s/kg for erythrocytes containing 100% metHb. Oxygenated erythrocytes had a magnetophoretic mobility of from -0.2 x 10(-6) mm(3) s/kg to +0.30 x 10(-6) mm(3) s/kg, indicating a significant diamagnetic component relative to the suspension medium, in agreement with previous studies on the hemoglobin magnetic susceptibility. Magnetophoresis may open up an approach to characterize and separate cells for biochemical analysis based on intrinsic and extrinsic magnetic properties of biological macromolecules.     

Magnetic-field-induced vertigo: a theoretical and experimental investigation

Vertigo-like sensations or apparent perception of movement are reported by some subjects and operators in and around high field whole body magnetic resonance body scanners. Induced currents (which modulate the firing rate of the vestibular hair cell), magneto-hydrodynamics (MDH), and tissue magnetic susceptibility differences have all been proposed as possible mechanisms for this effect. In this article, we examine the theory underlying each of these mechanisms and explore resulting predictions. Experimental evidence is summarised in the following findings: 30% of subjects display a postural sway response at a field-gradient product of 1 T(2)m(-1); a determining factor for experience of vertigo is the total unipolar integrated field change over a period greater than 1 s; the perception of dizziness is not necessarily related to a high value of the rate of change of magnetic field; eight of ten subjects reported sensations ranging from mild to severe when exposed to a magnetic field change of the order of 4.7 T in 1.9 s; no subjects reported any response when exposed to 50 ms pulses of dB/dt of 2 Ts(-1) amplitude. The experimental evidence supports the hypothesis that magnetic-field related vertigo results from both magnetic susceptibility differences between vestibular organs and surrounding fluid, and induced currents acting on the vestibular hair cells. Both mechanisms are consistent with theoretical predictions.