Analysis of magnetic material in the human heart, spleen and liver

Isothermal remanent magnetization (IRM) acquisition and alternating field (A.F.) demagnetization analyses were performed on human heart, spleen and liver samples resected from cadavers. The magnetic properties of the samples were measured both at 77K and at 273K. A.F. demagnetization was performed at 273K. Results from the analyses of the tissue indicate the presence of ferromagnetic, fine-grained, magnetically interacting particles which, due primarily to magnetic properties, are thought to be magnetite and/or maghemite. The presence of superparamagnetic particles can be inferred from the increase in saturation IRM values when measured at 77K compared with measurements at 273K and the decay of remanent magnetization upon warming from 77K. The concentration of magnetic material (assuming it is magnetite or maghemite) in the samples varies from 13.7 ng g-1 to 343 ng g-1, with the heart tissue generally having the highest concentration. The presence of magnetic material in these organs may have implications for the function of biogenic magnetite in the human body.     

Superparamagnetic Magnetite in the Upper Beak Tissue of Homing Pigeons

Homing pigeons have been subject of various studies trying to detect magnetic material which might be involved in magnetic field perception. Here we focus on the upper-beak skin of homing pigeons, a region that has previously been shown to contain nerves sensitive to changes of the ambient magnetic field. We localized Fe³⁺ concentrations in the subcutis and identified the material by transmission electronmicroscopy (TEM) as aggregates of magnetite nanocrystals (with grain sizes between 1 and 5 nm). The particles form clusters of 1–3 m diameter, which are arranged in distinct coherent elongated structures, associated with nervous tissue and located between fat cells. Complementary low-temperature magnetic measurements confirm the microscopic observations of fine-grained superparamagnetic particles in the tissue. Neither electron-microscopic nor magnetic measurements revealed any single-domain magnetite in the upper-beak skin tissue.     

Magnetic and structural properties of magnetite in radular teeth of chiton Acanthochiton rubrolinestus

The teeth of the Polyplacophora Chiton Acanthochiton Rubrolinestus contain biomineralized magnetite crystallites whose biological functions in relation to structure and magnetic properties are not well understood. Here, using superconducting quantum interference device (SQUID) magnetometry, we find that the saturation magnetization (σ(s)) and the Verwey transition temperature (T(v)) of tooth particles are 78.4 emu/g and 105 K, respectively. These values are below those of the stoichiometric magnetite. An in situ examination of the structure of the magnetite-bearing region within an individual tooth using high-resolution transmission electron microscopy indicates magnetite microcrystals form electron dense polycrystalline sheets with typical lengths of about 800 nm and widths of about 150 nm. These polycrystalline sheets are arranged regularly along the longitudinal direction of the tooth cutting surface. In addition, the crystallites in polycrystalline sheets take on generally good crystallinity. The magnetic microstructures of in situ magnetic force microscopy demonstrate that the [111] easy direction of magnetite microcrystals are aligned along the length of the tooth, whereas the [111] direction is parallel to the thickness of the tooth. Both M?ssbauer spectra and magnetization versus temperature measurements under field cooled and zero-field cooled conditions do not detect superparamagnetic magnetite crystallites in the mature major lateral tooth particles of this chiton.     

Does pigeon homing depend on stimuli perceived during displacement?

Summary In order to test whether stimuli perceived during passive displacement are important for the subsequent homing, pigeons were transported in an apparatus designed to prevent them from receiving relevant information: The experimental birds were continuously rotated quite rapidly (1.5 cps, radial acceleration about 4 g); in addition, they were exposed to an artificial magnetic field and supplied with bottled air. Control birds were transported in open-air cages on top of the van with free view to all sides.Five pairs of releases from equal distances in opposite directions were conducted. Experienced birds were released at distances of about 15, 90, and 300 km from the loft, inexperienced birds at distances of about 180km. In each pair of releases both groups of pigeons were significantly homeward oriented. Neither in initial orientation nor in homing performance nor in the distribution of recoveries were the experimental birds inferior to the controls or in any perceptable way different from them.It is concluded that homing of passively displaced pigeons is not primarily based on information gathered during the outward journey.Abbreviations EP experimental pigeon(s) - CP control pigeon(s) The possibility to maintain our pigeon loft in a building that belongs to the Zoological Institute (Prof. M. Lindauer) of the University of Würzburg is gratefully acknowledged.     

The osmotic magnetometer: a new model for magnetite-based magnetoreceptors in animals

Homing pigeons and migratory birds are well known examples for animals that use the geomagnetic field for their orientation. Yet, neither the underlying receptor mechanism nor the magnetoreceptor itself is known. Recently, an innervated structure containing clusters of magnetite nanocrystals was identified in the upper beak skin of the homing pigeon. Here we show theoretically that such a cluster has a magnetic-field-dependent shape, even in fields as weak as the Earth's magnetic field; by converting magnetic stimuli into mechanical strain, the clusters can be assumed as primary units of magnetoperception in homing pigeons. Since the orientation of the strain ellipsoid indicates the direction of the external magnetic field, a cluster of magnetite nanocrystals also has the potential to serve as the basis of the so-called inclination compass of migratory birds. It is quantitatively demonstrated that the magnetic-field-induced shape change of a cluster can be amplified as well as counterbalanced by means of osmotic pressure regulation, which offers an elegant possibility to determine the magnetic field strength just by measuring changes in concentration. Received: 18 May 1998 / Revised version: 11 February 1999 / Accepted: 11 February 1999     

Biogenic magnetite as a basis for magnetic field detection in animals

Bacteria, sharks, honey bees, and homing pigeons as well as other organisms seem to detect the direction of the earth's magnetic field. Indirect but reproducible evidence suggests that the bees and birds can also respond to very minute changes in its intensity. The mechanisms behind this sensitivity are not known. Naturally magnetic, biologically precipitated magnetite (Fe₃O₄) has been found in chitons, magnetotactic bacteria, honey bees, homing pigeons, and dolphins. Its mineralization in localized areas may be associated with the ability of these animals to respond to the direction and intensity of the earth's magnetic field. The presence of large numbers (～10⁸) of superparamagnetic magnetite crystals in honey bees and similar numbers of single-domain magnetite grains in pigeons suggests that there may be at least two basic types of ferrimagnetic magnetoreceptive organelles. Theoretical calculations show that ferrimagnetic organs using either type of grain when integrated by the nervous system are capable of accounting for even the most extreme magnetic field sensitivities reported. Indirect evidence suggests that organic magnetite may be a common biological component, and may account for the results of numerous high field and electromagnetic experiments on animals.     

Brieftauben

Homing pigeons Homing pigeons are well known for their excellent homing abilities which allow them to return to their lofts from unknown releasing sites more than hundreds of kilometres away. Several orientation mechanisms – sun compass, earth's magnetic field, olfactory cues, visual cues – are known to be involved in homing performance as well as parameters such as motivation and experience. New technology give an insight in their homing behaviour and track preferences and it is shown that homing pigeons physiology and neurobiology seem to be functionally adapted to homing. Pigeons races are still common and it is shown how the pigeon breeder tries to maximize the success of his pigeons.     

Magnetic analysis of human brain tissue

Fourteen samples of human hippocampal tissue were resected during amygdalo-hippocampectomies performed on patients suffering from Mesial Temporal Lobe Epilepsy (MTLE). In addition, eight tissue samples from the hippocampus, cortex basalganglia, cerebellum and leptomeninges were resected from cadavers during routine autopsy and were not chemically fixed. All samples were preserved in liquid nitrogen and magnetic properties were measured at 77K and 273K. Measurements indicate that there are no systematic variations in magnetic particle concentrations or magnetic properties between MTLE patients and non-pathologic tissue from the cadavers. The presence of superparamagnetic particles can be inferred due to differences in the saturation remanence acquired at 77K and 273K. This is a further indication that biogenic magnetite and/or maghemite present in the human brain likely is not primarily associated with geomagnetic field sensing as it is known to occur in other organisms     

Bat head contains soft magnetic particles: Evidence from magnetism

Recent behavioral observations have indicated that bats can sense the Earth's magnetic field. To unravel the magnetoreception mechanism, the present study has utilized magnetic measurements on three migratory species (Miniopterus fuliginosus, Chaerephon plicata, and Nyctalus plancyi) and three non‐migratory species (Hipposideros armiger, Myotis ricketti, and Rhinolophus ferrumequinum). Room temperature isothermal remanent magnetization acquisition and alternating‐field demagnetization showed that the bats' heads contain soft magnetic particles. Statistical analyses indicated that the saturation isothermal remanent magnetization of brains (SIRM_{1T_brain}) of migratory species is higher than those of non‐migratory species. Furthermore, the SIRM_{1T_brain} of migratory bats is greater than their SIRM_{1T_skull}. Low‐temperature magnetic measurements suggested that the magnetic particles are likely magnetite (Fe₃O₄). This new evidence supports the assumption that some bats use magnetite particles for sensing and orientation in the Earth's magnetic field. Bioelectromagnetics 31:499–503, 2010. © 2010 Wiley‐Liss, Inc.     

The avian hippocampus, homing in pigeons and the memory representation of large-scale space

The extraordinary navigational ability of homing pigeons providesa unique spatial cognitive system to investigate how the brainis able to represent past experiences as memory. In this paper,we first summarize a large body of lesion data in an attemptto characterize the role of the avian hippocampal formation(HF) in homing. What emerges from this analysis is the criticalimportance of HF for the learning of map-like, spatial representationsof environmental stimuli used for navigation. We then exploresome interesting properties of the homing pigeon HF, using fordiscussion the notion that the homing pigeon HF likely displayssome anatomical or physiological specialization(s), comparedto the laboratory rat, that account for its participation inhoming and the representation of large-scale, environmentalspace. Discussed are the internal connectivity among HF subdivisions,the occurrence of neurogenesis, the presence of rhythmic thetaactivity and the electrophysiological profile of HF neurons.Comparing the characteristics of the homing pigeon HF with thehippocampus of the laboratory rat, two opposing perspectivescan be supported. On the one hand, one could emphasize the subtledifferences in the properties of the homing pigeon HF as possibledeparture points for exploring how the homing pigeon HF maybe adapted for homing and the representation of large-scalespace. Alternatively, one could emphasize the similarities withthe rat hippocampus and suggest that, if homing pigeons representspace in a way different from rats, then the neural specializationsthat would account for the difference must lie outside HF. Onlyfuture research will determine which of these two perspectivesoffers a better approximation of the truth.     

The Orientational Consequences of Flocking Behaviour in Homing Pigeons,Columba livia

Two experiments are described which investigate the orientational consequences of flocking in homing pigeons Columba livia. Previous experiments have shown that homing pigeons placed inside a clear-sided release box for 5 min before release from a familiar site have enhanced ground homing speed compared with those placed in an opaque-sided box. It is assumed that previewing the surrounding landscape allows for faster homing since a bird denied this information must accumulate the knowledge on release. In experiment 1, using the same technique developed in these experiments but releasing the birds in pairs we showed that within familiar areas, homing pigeons can exploit a partner that has acquired more information, allowing them to home more quickly. In experiment 2 we attempted to test three potential strategies which may occur during homing flights. The results do not conclusively distinguish between these three mechanisms but suggest that orientation of the pairs of birds is most likely to have resulted from a compromise of individual tendencies, or from following the best homer, but not from following a ‘governing leader’. The consequence of these mechanisms is discussed.     

Accurate route demonstration by experienced homing pigeons does not improve subsequent homing performance in naive conspecifics.

We describe an experiment that uses the grouping tendencies and navigational abilities of the homing pigeon (Columba livia) to investigate the possibility of socially mediated information transfer in a field setting. By varying the composition of paired-release types, we allowed some naive birds to receive an accurate demonstration of the home route whilst others were paired with similarly naive conspecifics. After this 'paired phase', we predicted that if any learning of spatial information occurred then naive members of the former pairs would outperform their untutored conspecifics when re-released individually during the subsequent 'single phase' of the experiment. This prediction was not confirmed. Neither homing speed nor initial orientation was superior in individually released tutored versus untutored birds, despite the fact that both performance measures were better in the earlier 'paired phase' with experienced demonstrators. Our results suggest that although naive homing pigeons clearly interact with their experienced partners, they are unable to transfer any individually useful spatial information to subsequent homing flights.     

Evidence that pigeons orient to geomagnetic intensity during homing

The influence of the Earth's magnetic field on locomotory orientation has been studied in many taxa but is best understood for homing pigeons (Columba livia). Effects of experimentally induced and naturally occurring perturbations in the geomagnetic field suggest that pigeons are sensitive to changes in geomagnetic parameters. However, whether pigeons use the Earth's magnetic field for position determination remains unknown. Here we report an apparent orientation to the intensity gradient of the geomagnetic field observed in pigeons homing from sites in and around a magnetic anomaly. From flight trajectories recorded by GPS-based tracking devices, we noted that many pigeons released at unfamiliar sites initially flew, in some cases up to several kilometres, in directions parallel and/or perpendicular to the bearing of the local intensity field. This behaviour occurred irrespective of the homeward direction and significantly more often than what was expected by random chance. Our study describes a novel behaviour which provides strong evidence that pigeons when homing detect and respond to spatial variation in the Earth's magnetic field--information of potential use for navigation.     

Characterization of iron compounds in tumour tissue from temporal lobe epilepsy patients using low temperature magnetic methods

Excess iron accumulation in the brain has been shown to be related to a variety of neurodegenerative diseases. However, identification and characterization of iron compounds in human tissue is difficult because concentrations are very low. For the first time, a combination of low temperature magnetic methods was used to characterize iron compounds in tumour tissue from patients with mesial temporal lobe epilepsy (MTLE). Induced magnetization as a function of temperature was measured between 2 and 140 K after cooling in zero-field and after cooling in a 50 mT field. These curves reveal an average blocking temperature for ferritin of 10 K and an anomaly due to magnetite at 48 K. Hysteresis measurements at 5 K show a high coercivity phase that is unsaturated at 7 T, which is typical for ferritin. Magnetite concentration was determined from the saturation remanent magnetization at 77 K. Hysteresis measurements at various temperatures were used to examine the magnetic blocking of magnetite and ferritin. Our results demonstrate that low temperature magnetic measurements provide a useful and sensitive tool for the characterisation of magnetic iron compounds in human tissue.Published online: March 2005     

空气污染对信鸽比赛个体归巢速度的影响

空气污染作为一种有害的环境因素,对人类及动物的生理、心理均有影响.在鸟类中,信鸽(Columba livia)是研究空气污染影响的理想模型.为探究空气污染的行为学效应,通过收集并筛选2018和2019年成都市信鸽协会春秋两个季节举办的64场赛事共285羽参赛5场及以上的信鸽不同空距等级下的归巢速度,利用混合线性模型分析...     

Konditionierung verfrachteter Brieftauben: eine ?neue“ Methode zur Analyse der Karte von Brieftauben

Zusammenfassung Es wird vorgeschlagen, mit Hilfe klassischer Konditionierung sowohl die physikalischen Charakteristika als auch die Verteilung der bei der Navigation von Tauben relevanten Faktoren zu überprüfen. Dabei wird ein neutraler, physikalisch eindeutig definierbarer Reiz mit der Heimkehrreaktion verfrachteter Brieftauben verknüpft. In standardisierten Versuchsreihen kann die Schnelligkeit, mit der Tauben die neue Reizmodalität mit der Aufgabe assoziieren, nach Hause zu fliegen, als Maß für die biologische Relevanz des Reizes dienen. Weiterhin kann mit dieser Methode im Freiland überprüft werden, ob die Taube mit einer vorgegebenen Reizmodalität einen Ort, eine Region oder eine Verfrachtungsrichtung assoziiert. Vorläufige Resultate einer laufenden Arbeit zeigen, daß Tauben in Heimkehrexperimenten auf künstliche Reize (im vorliegenden Fall Geruchsreize) konditioniert werden können. Die hiermit erhaltenen Ergebnisse sollten spezifischere Vorhersagen über mögliche Karteninformation erlauben als bisher, die dann experimentell getestet werden können.

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Conditioning of homing pigeons en route and at the release site: a new method to assess the map component

Summary The present study suggests classical conditioning as a possibility to assess the elusive map of the homing pigeon. In classical conditioning a previously neutral stimulus is associated with an already existing response. In case of the study of pigeon homing well defined physical cues (such as odours, magnetic fields or infrasound) can be presented to the pigeons prior to release. After a series of training sessions the pigeon learns to associate a given stimulus with a certain home direction.According to the preliminary results of this ongoing study, pigeons can learn in homing experiments to associate artificial odours with different home directions. Pigeons have been trained to associated amylacetate with releases from different sites located north of home and benzaldehyde with releases from the south. Exchange of the two odours for the experimental pigeons after ten training sessions results in impaired initial orientation and reduced homing speed of experimentals compared to controls when released at new sites.In comparative studies the time needed to achieve a preset level of performance could be used to rate the biological significance of different stimuli for homing. By releasing conditioned pigeons at different sites it can also be tested whether or not the simulus is being associated with a site, a region or a direction with respect to home. With this approach the distribution as well as the physical characteristics of different cues can be evaluated for their potential as information relevant for pigeon homing.

     

Bar magnets mask the effect of normal magnetic disturbances on pigeon orientation

Summary In a previous publication we reported a correlation between normal fluctuations of the earth's magnetic field and the day-to-day variations in the initial bearings chosen by homing pigeons released repeatedly at a single test site under sunny skies. We here examine the question whether this correlation reflects a cause-and-effect relationship. A series of 20 test releases was conducted in 1974 to compare the bearings of pigeons wearing bar magnets glued to their backs with the bearings of pigeons wearing brass bars. As in a pilot series conducted in 1970, the day-to-day variations in the bearings of the birds wearing brasses were inversely correlated with the variations in the K index of magnetic disturbance, whereas no such correlation was found for the bearings of the birds wearing magnets. We conclude that the magnets mask the effect of the K fluctuations, which suggests that it is the magnetic events themselves that influence the orientational response of normal pigeons. This conclusion is further supported by a demonstration that bar magnets, like natural magnetic disturbances, deflect the birds' bearings to the left.This research was supported by Grants BMS 72-02198-AO2 and BMS 75-18905-A02 from the National Science Foundation.     

Olfaction and homing in pigeons: Nerve-section experiments,critique, hypotheses

Summary At four sites in the cardinal directions from the home loft in about 180 km distance, 135 experimental pigeons (EPs) and 171 control pigeons (CPs) were released. The EPs had been made anosmic by bilateral olfactory nerve section. All birds were completely inexperienced in homing.Homeward orientation was clearly established in the CPs of which 19% returned to the loft. The performances of the EPs were significantly worse in (a) initial orientation, (b) vanishing intervals, (c) distribution of recoveries, and (d) homing success (none of them homed).The EPs still showed the loft-specific preferred compass direction (PCD).The recoveries of the EPs are much more widely scattered in direction than those of the rather well homeward oriented CPs, even if the distances from the release site are the same in both groups. It is concluded that the navigational capability rather than the motivation to fly or to return home is affected by olfactory deprivation. It is further concluded that homing of pigeons depends on olfactory stimuli perceived at the remote sites even at distances as large as 180km.In the data of the anosmic pigeons a non-olfactory component of homeward orientation persists which is much more pronounced on the W-E axis than on the N-S axis. This component alone appears to be insufficient for a return to the loft.Earlier results and conclusions that gave rise to some controversy are critically examined.The present as well as earlier findings are discussed with respect to two alternative hypotheses of olfactory navigation, the mosaic hypothesis (favoured by Papi) and the gradient hypothesis (favoured by the author).Abbreviations EP experimental pigeon(s) - CP control pigeon(s) - CLCP cueless transported control pigeon(s) (see p. 210) - PCD preferred compass direction I gratefully acknowledge the possibility to maintain our pigeon loft in a building that belongs to the Zoological Institute (Prof. M. Lindauer) of the University of Würzburg. I thank B. and K. Brendle, E. Thiele, and K. Wielander for the releasing of pigeons and for other technical assistance.     

Do release-site biases reflect response to the Earth's magnetic field during position determination by homing pigeons?

How homing pigeons (Columba livia) return to their loft from distant, unfamiliar sites has long been a mystery. At many release sites, untreated birds consistently vanish from view in a direction different from the home direction, a phenomenon called the release-site bias. These deviations in flight direction have been implicated in the position determination (or map) step of navigation because they may reflect local distortions in information about location that the birds obtain from the geophysical environment at the release site. Here, we performed a post hoc analysis of the relationship between vanishing bearings and local variations in magnetic intensity using previously published datasets for pigeons homing to lofts in Germany. Vanishing bearings of both experienced and naïve birds were strongly associated with magnetic intensity variations at release sites, with 90 per cent of bearings lying within ±29° of the magnetic intensity slope or contour direction. Our results (i) demonstrate that pigeons respond in an orderly manner to the local structure of the magnetic field at release sites, (ii) provide a mechanism for the occurrence of release-site biases and (iii) suggest that pigeons may derive spatial information from the magnetic field at the release site that could be used to estimate their current position relative to their loft.     

Normal fluctuations in the earth's magnetic field influence pigeon orientation

Summary In an attempt to determine whether naturally occurring fluctuations in the earth's magnetic field influence homing pigeons' initial bearings, three series of test releases (1970, 1972, 1973) at a site 45.7 miles north of the loft were conducted under an experimental design that controlled for most extraneous variables. The mean bearings for each series showed a significant inverse correlation with the K index of magnetic activity, i.e. the bearings were more to the left when K was high. In a single series of releases at a site 43.6 miles west of the loft, the means again showed a significant inverse correlation with K. Since most of the magnetic fluctuations in all four series were less than 70 gamma, it is concluded that the sensitivity of pigeons to magnetic cues probably approaches that already demonstrated for honeybees. A brief discussion of Lamotte's (1974) paper concerning the effect of bar magnets on initial orientation is appended.