Ferromagnetic crystals (magnetite?) in human tissue

In recent years, a variety of animals have been found which are able to synthesize the ferromagnetic mineral magnetite (Fe3O4). Lowenstam (1962) originally recognized biogenic magnetite in the radular teeth of a primitive marine mollusc, the chiton (Polyplacophora), and since then it has been identified as a precipitate in several magnetically sensitive organisms, including honey bees (Gould, Kirschvink & Deffeyes, 1978), homing pigeons (Walcott, Gould & Kirschvink, 1979) and in magnetotactic bacteria (Frankel, Blakemore & Wolfe, 1979). Zoeger, Dunn & Fuller (1980) also report a localized concentration of magnetite in dolphin heads, although magnetosensory behavioural experiments have not as yet been done on them. Magnetite is biologically unique because it is both ferromagnetic and conducts electricity like a metal; consequently it interacts strongly with magnetic and electric fields. Due to the numerous industrial and research environments which expose people to artificially intense electromagnetic conditions, it is of importance to know whether or not this material might exist in human tissue. Kirschvink & Gould (1980) have argued that there are probably one or more non-sensory metabolic functions for magnetite from which specialized magnetoreceptors could have evolved; consequently one might expect to find small amounts of magnetite in all animals, including humans. In an attempt to partially answer this question, I searched for magnetic remanence in four intact human adrenal glands which had been removed during autopsy and were frozen quickly in non-magnetic containers. Results of this analysis are shown on Fig. 1. Indeed, there is a measurable amount of high-coercivity ferromagnetic material present which appears to be finely disseminated throughout the tissue. Between 1 and 10 million single-domain magnetite crystals per gram would be necessary to account for the observed magnetic remanence. Although these measurements do not uniquely identify the crystal phase as magnetite, no other ferromagnetic minerals have ever been observed as biologic precipitates. Positive identification, of course, awaits the development of magnetic separation techniques capable of isolating and purifying these submicroscopic crystals. Barnothy & Sümegi (1969) have shown that mouse adrenals are particularly prone to degeneration in moderately strong magnetic fields; this effect might be due to the presence of magnetite

Palaeomagnetic Study on the Precambrian-Cambrian Boundary Candidate Stratotype Section at Meishucun, Yunnan

The Meishucun secton has been recommended as an international candidate stratotype secton of the Precambrian-Cambrian boundary. The paper deals with the palaeomagnetic study on the section. A total of 159 palaeomagnetic samples were successively collected from the platform-facies sequence of carbonates and phosphates at the section. Thermal demagnetization results indicate a great majority of the rocks at the section have been strongly overprinted by recent magnetic field, but 57 samples have preserved remanent magnetization with antipodal directions (mean D /1 = 4.2 ° / 7.1 °, K= 9, Α 95 = 6.6 ° ). Baaed on calculation, the location of the palaeomagnetic pole was at 68.8 ° N and 270.7 ° E, which is different from any palaeopoles obtained from younger Phanerozoic rocks in South China. The results reveal a polarity zonation which includes at least 9 reversal events. A comparison of China' s magnetostratigraphic records with those from Siberia, Australia and the western U.S.A. shows that all the sections are characterized by frequent polarity reversals'.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73060/1/j.1755-6724.1991.mp4001009.x.pd

The Earth's Worst Climate Disaster

Scientists, environmentalists, and the wiser members of the political class worry today about global climate change. Will rising tides plunge Tokyo, London, and New York beneath the ocean’s waves? Will meltwater pouring off of North America shift the circulation of the North Atlantic Ocean and plunge Europe into an Ice Age? Yet, as worrisome as these prospects are, the Earth has faced far greater climatic catastrophes in the past. The greatest among these was the Paleoproterozoic Snowball Earth event, which 2.3 billion years ago smothered the planet with a blanket of ice for tens of millions of years

The identification and biogeochemical interpretation of fossil magnetotactic bacteria

Magnetotactic bacteria, which most commonly live within the oxic-anoxic transition zone (OATZ) of aquatic environments, produce intracellular crystals of magnetic minerals, specifically magnetite or greigite. The crystals cause the bacteria to orient themselves passively with respect to the geomagnetic field and thereby facilitate the bacteria’s search for optimal conditions within the sharp chemical gradients of the OATZ. The bacteria may also gain energy from the redox cycling of their crystals. Because magnetotactic bacteria benefit from their magnetic moments, natural selection has promoted the development of traits that increase the efficiency with which the intracellular crystals impart magnetic moments to cells. These traits also allow crystals produced by magnetotactic bacteria (called magnetofossils when preserved in sediments) to be distinguished from abiogenic particles and particles produced as extracellular byproducts of bacterial metabolism. Magnetofossils are recognizable based on their narrow size and shape distributions, distinctive morphologies with blunt crystal edges, chain arrangement, chemical purity, and crystallographic perfection. This article presents a scheme for rating magnetofossil robustness based on these traits. The magnetofossil record extends robustly to the Cretaceous and with lesser certainty to the late Archean. Because magnetotactic bacteria predominantly live in the OATZ, the abundance and character of their fossils can reflect environmental changes that alter the chemical stratification of sediments and the water column. The magnetofossil record therefore provides an underutilized archive of paleoenvironmental information. Several studies have demonstrated a relationship between magnetofossil abundance and glacial/interglacial cycles, likely mediated by changes in pore water oxygen levels. More speculatively, a better-developed magnetofossil record might provide constraints on the long-term evolution of marine redox stratification. More work in modern and ancient settings is necessary to explicate the mechanisms linking the abundance and character of magnetofossils to ancient biogeochemistry

Paleoproterozic Icehouses and the Evolution of Oxygen Mediating Enzymes: The Case for a Late Origin of Photosystem -- II

Two major geological problems regarding the origin of oxygenic photosynthesis are: (1) identifying a source of oxygen predating biological oxygen production and capable of driving the evolution of oxygen tolerance, and (2) determining when oxygenic photosynthesis evolved. One solution to the first problem is the accumulation of photochemically-produced H2O2 at the surface of glaciers and its subsequent incorporation into ice. Melting at the glacier base would release H2O2, which interacts with seawater to produce O2 in an environment shielded from the lethal levels of ultraviolet radiation needed to produce H2O2. Answers to the second problem are controversial and range from 3.8 to 2.2 Ga. A skeptical view, based on metals that have redox potentials close to oxygen, argues for the late end of the range. The preponderance of geological evidence suggests little or no oxygen in the late Archaean atmosphere (< 1 ppm). The main piece of evidence for an earlier evolution of oxygenic photosynthesis comes from lipid biomarkers. Recent work, however, has shown that 2-methylhopanes, once thought to be unique biomarkers for cyanobacteria, are also produced anaerobically in significant quantities by at least two strains of anoxygenic phototrophs. Sterane biomarkers provide the strongest evidence for a date ≥2.7 Ga but could also be explained by the common evolutionary pattern of replacing anaerobic enzymes with oxygen-dependent ones. Although no anaerobic sterol synthesis pathway has been identified in the modern biosphere, enzymes that perform the necessary chemistry do exist. This analysis suggests that oxygenic photosynthesis could have evolved close in geological time to the Makganyene Snowball Earth Event and argues for a causal link between the two

How does the franchisor’s choice of different control mechanisms affect franchisees’ and employee-managers’ satisfaction?

Satisfaction of franchisees and employee-managers affects the overall performance of a franchise system. We argue that different actors in the same franchise system need to be treated in different ways. The franchisor’s choice of control mechanisms affects the satisfaction of franchisees and employee-managers differently. Drawing on data from the largest German franchise system, we show that the effectiveness of different control mechanisms depends on actor type and experience. Outcome control leads to higher satisfaction among franchisees and employee-managers, while behavior control enhances employee-managers’ satisfaction. Thereby, outcome control leads to higher satisfaction among more experienced franchisees, while behavior control enhances both highly and lowly experienced employee-managers’ satisfaction. Our results suggest that franchisors face a dilemma: On the one hand, behavior control is associated with high costs and has no impact on franchisees’ satisfaction at all. On the other hand, it might still be necessary to prevent franchisees from behaving opportunistically

Ferromagnetism in two mouse tumours

A variety of living organisms has been found recently that are biochemically able to precipitate the ferromagnetic mineral magnetite (Fe3O4). Originally discovered in the radular teeth of a primitive marine mollusc (Lowenstam, 1962), magnetite has since been reported in bacteria (Frankel, Blakemore & Wolfe, 1979), arthropods (Gould, Kirschvink & Deffeyes, 1978), and vertebrates (Walcott, Gould & Kirschvink, 1979; Zoeger, Dunn & Fuller, 1981; Walker & Dizon, 1981). Although the presence and biological origin of this material are clear, very little is yet known about the distribution or metabolic function of ferromagnetic minerals in vertebrate tissue. Magnetic remanence, which uniquely indicates the presence of ferromagnetic particles, has been previously detected in localized areas associated with the dura membranes of homing pigeons (Walcott et al. 1979) and dolphins (Zoeger et al. 1981), in pigeon neck muscles (Presti & Pettigrew, 1980), in the mid-brain of monkeys, and in human adrenal glands (Kirschvink, 1981). We report here the first discovery of anomalously high concentrations of ferromagnetic material in two strains of neoplasms, YC-8 lymphoma and Lewis lung tumour, as well as the apparent absence of such material in three human carcinomas (gastric, colon and renal)

Biophysics of magnetic orientation: strengthening the interface between theory and experimental design

The first demonstrations of magnetic effects on the behaviour of migratory birds and homing pigeons in laboratory and field experiments, respectively, provided evidence for the longstanding hypothesis that animals such as birds that migrate and home over long distances would benefit from possession of a magnetic sense. Subsequent identification of at least two plausible biophysical mechanisms for magnetoreception in animals, one based on biogenic magnetite and another on radical-pair biochemical reactions, led to major efforts over recent decades to test predictions of the two models, as well as efforts to understand the ultrastructure and function of the possible magnetoreceptor cells. Unfortunately, progress in understanding the magnetic sense has been challenged by: (i) the availability of a relatively small number of techniques for analysing behavioural responses to magnetic fields by animals; (ii) difficulty in achieving reproducible results using the techniques; and (iii) difficulty in development and implementation of new techniques that might bring greater experimental power. As a consequence, laboratory and field techniques used to study the magnetic sense today remain substantially unchanged, despite the huge developments in technology and instrumentation since the techniques were developed in the 1950s. New methods developed for behavioural study of the magnetic sense over the last 30 years include the use of laboratory conditioning techniques and tracking devices based on transmission of radio signals to and from satellites. Here we consider methodological developments in the study of the magnetic sense and present suggestions for increasing the reproducibility and ease of interpretation of experimental studies. We recommend that future experiments invest more effort in automating control of experiments and data capture, control of stimulation and full blinding of experiments in the rare cases where automation is impossible. We also propose new experiments to confirm whether or not animals can detect magnetic fields using the radical-pair effect together with an alternate hypothesis that may explain the dependence on light of responses by animals to magnetic field stimuli