Phenomenon Of Imprinting Research Articles

Abstract 193: Dissecting satellite and imprinting genes methylation status in cloned bovine: Aberrant methylation in imprinting loci

Abstract In mammals, genome-wide epigenetic reprogramming systems exist in primordial germ cells and zygote. It plays a crucial role in regulating genome functions at critical stages of embryo development and confers stability of gene expression during mammalian development. Inappropriate reprogramming of donor nuclei in somatic cell resulted in neonatal death and preimplantation defects during animal cloning technique. Specific demethylation events in differentiated tissues could then lead to further changes in gene expression as needed. In this study, six cloned bovines created by ear fibroblast nuclear transfer with short life span and multiple organ defects were used as the experimental materials. We focus on three imprinting genes included two growth factor genes IGF-2, H19 and Xist (X chromosome inactive regulated gene) by combined bisulfite and restriction assay (COBRA). Bisulfite sequencing was also applied to analyze the aberrant CpG sites in different imprinted genes loci in these cloned bovine genomes. Our data show that loss of imprinting (LOI) phenomenon was frequently appeared in IGF-2, Xist and H19 imprinted loci in several tissues of these cloned bovines. Furthermore, we detected the cloned bovine NTG-2 expression of these imprinting genes with quantitative real time PCR (Q-PCR). The data suggested that IGF-2 and H19 are extremely overexpressed in liver, vein, ear, skin and uterus. The IGF-2 mRNA expression in uterus and liver of NTG-2 cow are almost 1,200 and 800 folds compared to WT cow. The H19 expression level in liver of NTG-2 also exhibited a 34,000-fold higher than that of WT cow. According to our research, the extensively overexpression of IGF-2 and H19, probably were the major reason to cause the cloned bovine NTG-2 not only organ defects, but also aberrant embryonic development. In conclusion, the death of clones may be due to aberrant DNA methylation at the loci of imprinting genes and disruption of incompletely reprogrammed after nuclear transfer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 193.

Somatic development and embryo yield in crossbred F1 mice generated by different mating strategies

The aim of this study was to evaluate different mating strategies among endogamic strains to create F1 populations of mice, minimising the effect of inbreeding depression on somatic development and embryo yield. Females from the strains Swiss, CBA and C57Bl/6 were divided in nine experimental mate arrangements. The total numbers of pups born alive per dam and somatic development, estimated by weighing and measuring the crown-rump length, were recorded. Superovulation response was evaluated in outbreed females. Litter size differed among endogamic dams, irrespective of the sire. Somatic development results suggest heterosis and imprinting phenomena, once a differential parental effect was demonstrated. There was no difference in corpora lutea, ova or embryos recovered (P > 0.05), but recovery and viability rates differ among F1 groups (P < 0.05). The association of dam prolificity with somatic development and superovulation response of the pups should be considered for experimental F1 populations establishment. The use of outbreed animals, however, did not reduce response variability to hormone treatment.

Glucose Metabolism, Islet Architecture, and Genetic Homogeneity in Imprinting of [Ca2+]i and Insulin Rhythms in Mouse Islets

We reported previously that islets isolated from individual, outbred Swiss-Webster mice displayed oscillations in intracellular calcium ([Ca2+]i) that varied little between islets of a single mouse but considerably between mice, a phenomenon we termed “islet imprinting.” We have now confirmed and extended these findings in several respects. First, imprinting occurs in both inbred (C57BL/6J) as well as outbred mouse strains (Swiss-Webster; CD1). Second, imprinting was observed in NAD(P)H oscillations, indicating a metabolic component. Further, short-term exposure to a glucose-free solution, which transiently silenced [Ca2+]i oscillations, reset the oscillatory patterns to a higher frequency. This suggests a key role for glucose metabolism in maintaining imprinting, as transiently suppressing the oscillations with diazoxide, a KATP-channel opener that blocks [Ca2+]i influx downstream of glucose metabolism, did not change the imprinted patterns. Third, imprinting was not as readily observed at the level of single beta cells, as the [Ca2+]i oscillations of single cells isolated from imprinted islets exhibited highly variable, and typically slower [Ca2+]i oscillations. Lastly, to test whether the imprinted [Ca2+]i patterns were of functional significance, a novel microchip platform was used to monitor insulin release from multiple islets in real time. Insulin release patterns correlated closely with [Ca2+]i oscillations and showed significant mouse-to-mouse differences, indicating imprinting. These results indicate that islet imprinting is a general feature of islets and is likely to be of physiological significance. While islet imprinting did not depend on the genetic background of the mice, glucose metabolism and intact islet architecture may be important for the imprinting phenomenon.

Structural and dielectric properties of Ba 0.5Sr 0.5(Sn xTi 1− x)O 3 ceramics obtained by the soft chemical method

Ba 0.5Sr 0.5(Sn x Ti 1− x )O 3ceramics with different compositions ( x = 0 , 0.05, 0.10 and 0.20) were synthesized by the soft chemical method. X-ray diffraction patterns and Rietveld refinements revealed that these ceramics crystallize in a cubic structure. Secondary phases (BaSnO 3) were verified in Ba 0.5Sr 0.5(Sn x Ti 1− x )O 3 ceramics with Sn content x ≥ 0.10 . Raman spectra indicated a reduction in the Raman-active modes with the increase of Sn content in the lattice. Dilatometric measurements were used to analyze the sintering temperature behavior of these materials. Dielectric properties were investigated as a function of applied frequency. The increase in the remanent polarization was attributed to the imprint phenomenon due to the formation of oxygen vacancies. The domain pinning and the formation of BaSnO 3 phase favored the increase in the coercive fields.

A Mechanistic View of Genomic Imprinting

Genomic imprinting results in the expression of genes in a parent-of-origin-dependent manner. The mechanism and developmental consequences of genomic imprinting are most well characterized in mammals, plants, and certain insect species (e.g., sciarid flies and coccid insects). However, researchers have observed imprinting phenomena in species in which imprinting of endogenous genes is not known to exist or to be developmentally essential. In this review, I survey the known mechanisms of imprinting, focusing primarily on examples from mammals, where imprinting is relatively well characterized. Where appropriate, I draw attention to imprinting mechanisms in other organisms to compare and contrast how diverse organisms employ different strategies to perform the same process. I discuss how the various mechanisms come into play in the context of the imprint life cycle. Finally, I speculate why imprinting may be more widely prevalent than previously thought.

Trypanotolerance effect as a result of genomic imprinting in F2 murine population

African tsetse-fly transmitted trypanosomosis affects a wide range of wild and domesticated animal species. Trypanotolerance, the ability of some breeds to withstand the infection has been recognized and provides a sustainable option in animal production. While a genetic contribution, several behavioural traits are not in doubt, an attempt to find the responsible genes has proven to be complicated. One advance towards generating trypanotolerant animals has been the demonstration of an effective genetic imprinting phenomenon in crossbred mice, similar to that observed following challenge. We report a novel reciprocal crossing strategy that exploits epistasis and heterosis in inbred mouse strains to identify imprinting effect controlling trypanosomosis using an F2 (129/J x C57BL/6) resource populations. The results indicate that genetic control for trypanotolerance is complicated and the identification of imprinting effect may provide new insights of introgressing trypanotolerance in livestock Kenya Veterinarian Vol. 31 (2) 2007: pp. 68-71

WebWatch

BioTechniquesVol. 44, No. 4 WebWatchOpen AccessWebWatchKevin Ahern†Kevin Ahern††-Kevin Ahern - Please send web site recommendations to E-mail Address: ahernk@orst.eduSearch for more papers by this authorPublished Online:16 May 2018https://doi.org/10.2144/000112783AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinkedInRedditEmail Growing with the GrainThough it derives inspiration from the Grameen Bank, which makes loans to poor women in emerging economies, Gramene takes a decidedly different approach to improving the world, by trading in the currency of information, not money. The site, which is designed as a resource for comparative grass genomics, provides a cornucopia of research data on rice, sorghum, corn, wheat, barley, oats, and millet. Visitors can browse assembled genomes, search for protein structures, compare genetic maps, find genetic markers, examine phenotype-related loci, scan metabolic pathways, browse relevant literature, and upload information. They can also stay on top of news in the field, and there are even tutorials for newbies. That's a breakfast of champions for researchers and a relatively easy way to stay on top of this rapidly changing “landscape.”@ www.gramene.orgEpigenome HomeWe think of phenotypes as manifestations of nature and nurture, but the more the molecular underpinnings of biology are determined, the more there is to marvel about their complexity. For example, it is apparent that there is more to the nature component than genotype. Witness the epigenomic phenomena of imprinting, gene silencing, X chromosome inactivation, position effects, and bookmarking, which can all vary in an organism, despite the fact that the cells have identical DNA sequences. Experience the excitement of this rapidly evolving field at the Epigenome Network of Excellence.@ www.epigenome-noe.netPro-CreativeWhen was the last time you were asked to pontificate or “commentate”? If you're like most of us, you probably can't remember, but this can be changed quickly on your first visit to Science Creative Quarterly (SCQ), where scientists’ opinions and literary talents not only matter, but are encouraged. With a format aimed at bringing out researchers’ “inner voices,” David Ng's SCQ provides online opportunities to expand the creative horizons of its visitors. Looking for a laugh? You'll enjoy the humor section, which is peppered with funny articles like “Glacier Restoration Project Creeps Forward” or “Miracle on the 34th Replicate.” Serving a large spectrum spanning nerdy but talented writers to hungry readers, SCQ is indeed a rare medium, well done.@ www.scq.ubc.ca©2005 http://www.epigenome-noe.net/researchtools/protocol.php?protid=23Fume-Free FunPeople who like chemistry but can't stand to wear goggles and lab jackets don't have many options in pursuing their passion. They can (i) abandon the subject altogether or (ii) work in a virtual lab. The latter has several advantages, including numerous opportunities to learn without getting one's hands dirty and at virtually no expense, since the costs of chemicals, waste disposal, and the hazards of exposure are all virtual, too. If such a setup is your cup of tea, you should check out the ChemCollective. Noteworthy for its strong educational content, a pricing scheme that fits into any budget, and the complete absence of chemicals, the site works for both students and faculty, with content that includes not only clever lab exercises, but also tutorials for students and activities for instructors. There's even a mystery to solve.@ www.chemcollective.orgFlocks of LOXWhen it comes to enzymes linked to discomfort, you'll have to look pretty hard to find a more troublesome set than the lipoxygenases (LOX). The catalysts for forming leukotrienes and related compounds from arachidonic acid in animals (and linolenic acid in plants), lipoxygenases produce molecules implicated in inflammation, asthma, arthritis, and cancer. Ouch! Through knowledge comes power, though, and the LipOXygenases DataBase (LOX-DB) is a significant force, empowering researchers and helping them tackle these problems. It works by providing tools common to modern molecular research, including aligned sequences, ribbon diagrams, BLASTing, and sequence comparison matrices. A searchable reference section and another describing the relationship between LOX products and cancer round out this interesting site.@ www.dkfz.de/spec/lox-db/FiguresReferencesRelatedDetails Vol. 44, No. 4 Follow us on social media for the latest updates Metrics Downloaded 151 times History Published online 16 May 2018 Published in print April 2008 Information© 2008 Author(s)PDF download

Epithelial Progeny of Estrogen-Exposed Breast Progenitor Cells Display a Cancer-like Methylome

Estrogen imprinting is used to describe a phenomenon in which early developmental exposure to endocrine disruptors increases breast cancer risk later in adult life. We propose that long-lived, self-regenerating stem and progenitor cells are more susceptible to the exposure injury than terminally differentiated epithelial cells in the breast duct. Mammospheres, containing enriched breast progenitors, were used as an exposure system to simulate this imprinting phenomenon in vitro. Using MeDIP-chip, a methylation microarray screening method, we found that 0.5% (120 loci) of human CpG islands were hypermethylated in epithelial cells derived from estrogen-exposed progenitors compared with the non-estrogen-exposed control cells. This epigenetic event may lead to progressive silencing of tumor suppressor genes, including RUNX3, in these epithelial cells, which also occurred in primary breast tumors. Furthermore, normal tissue in close proximity to the tumor site also displayed RUNX3 hypermethylation, suggesting that this aberrant event occurs in early breast carcinogenesis. The high prevalence of estrogen-induced epigenetic changes in primary tumors and the surrounding histologically normal tissues provides the first empirical link between estrogen injury of breast stem/progenitor cells and carcinogenesis. This finding also offers a mechanistic explanation as to why a tumor suppressor gene, such as RUNX3, can be heritably silenced by epigenetic mechanisms in breast cancer.

&lt;b&gt;Imprinting in Fish: a Little Explored Phenomenon with Possible Implications for Fish Welfare&lt;/b&gt;

Imprinting, an early learning process that can determine later preferences for particular types of stimuli, is usually not a consideration in many activities related to fish. However, disruption of such learning and/or absence of suitable conditions for the development of preferences are frequent despite the lack of appropriate knowledge regarding the effects that these practices may have on later behaviour and health. The present study reviews the phenomenon of imprinting in fish and discusses its possible influence on fish welfare. Although there is also potential for acoustic imprinting, here we discuss how sexual, filial and olfactory imprinting should be considered when addressing welfare issues in fish. The review focuses on the relatively few fish species in which this phenomenon has been mainly researched, the results often proving that it may affect some behaviour patterns and social preferences. A diversity of factors, including species, context, behavioural repertoire and social systems may affect the actual existence of the phenomenon, although conditions normally prevailing in husbandry and other systems are not adjusted to allow the emergence of the process. Likewise, the effects of imprinting (or its absence) on fish welfare have still to be demonstrated in many fish species and should constitute a matter for further studies. The conclusion is drawn that much more needs to be learned. However, a better understanding of the relationship between this early learning process in fish and welfare is essential if a complete analysis of conditions promoting fish welfare is to be made.

Design of molecular imprinted polymers compatible with aqueous environment

The main problem of poor water compatibility of molecularly imprinted polymers (MIPs) was addressed in examples describing design of synthetic receptors with high affinity for drugs of abuse. An extensive potentiometric titration of 10 popular functional monomers and corresponding imprinted and Blank polymers was conducted in order to evaluate the subtleties of functional groups ionisation under aqueous conditions. It was found that polymers prepared using 2-trifluoromethacrylic acid (TFMAA) in combination with toluene as porogen possess superior properties which make them suitable for effective template recognition in water. The potential impact of phase separation during polymerisation on formation of high quality imprints has been discussed. Three drugs of abuse such as cocaine, deoxyephedrine and methadone were used as template models in polymer preparation for the practical validation of obtained results. The polymer testing showed that synthesized molecularly imprinted polymers have high affinity and selectivity for corresponding templates in aqueous environment, with imprinting factors of 2.6 for cocaine and 1.4 for methadone and deoxyephedrine. Corresponding Blank polymers were unable to differentiate between analytes, suggesting that imprinting phenomenon was responsible for the recognition properties.

Microscopic local fatigue in PZT thin films

The reduction in switchable polarization during fatigue largely limits the application of PZT thin films in ferroelectric nonvolatile memories. So, it is very important to understand the fatigue mechanism in PZT films, especially at a nanoscale level. In this paper, nanoscale fatigue properties in PZT thin films have been studied by piezoresponse force microscopy and local piezoloops. It has been found that a piezoloop obtained on a fatigued point exhibits a much more pinched shape and a local imprint phenomenon is observed after severe fatigue. Furthermore, the domain structure evolves from a simple single-peak profile to a complex fluctuant one. However, there is only some shift of the piezoloop when a unipolar field with the same amplitude is applied on the film. The available experimental data show that there exist obvious domain wall pinning and injection of electrons into the film during fatigue. Finally, a schematic illustration is suggested to explain the possible fatigue mechanism.

Direct linkage of mitochondrial genome variation to risk factors for type 2 diabetes in conplastic strains

Recently, the relationship of mitochondrial DNA (mtDNA) variants to metabolic risk factors for diabetes and other common diseases has begun to attract increasing attention. However, progress in this area has been limited because (1) the phenotypic effects of variation in the mitochondrial genome are difficult to isolate owing to confounding variation in the nuclear genome, imprinting phenomena, and environmental factors; and (2) few animal models have been available for directly investigating the effects of mtDNA variants on complex metabolic phenotypes in vivo. Substitution of different mitochondrial genomes on the same nuclear genetic background in conplastic strains provides a way to unambiguously isolate effects of the mitochondrial genome on complex traits. Here we show that conplastic strains of rats with identical nuclear genomes but divergent mitochondrial genomes that encode amino acid differences in proteins of oxidative phosphorylation exhibit differences in major metabolic risk factors for type 2 diabetes. These results (1) provide the first direct evidence linking naturally occurring variation in the mitochondrial genome, independent of variation in the nuclear genome and other confounding factors, to inherited variation in known risk factors for type 2 diabetes; and (2) establish that spontaneous variation in the mitochondrial genome per se can promote systemic metabolic disturbances relevant to the pathogenesis of common diseases.

CONSERVATION OF IMPRINTING IN SWINE AND COMPARATIVE ASPECTS OF IMPRINTING

Imprinted genes have been identified in placental mammals, and marsupials but not in egg-laying mammals (monotremes), birds, fishes, reptiles, or amphibians, suggesting that the phenomena of genomic imprinting and placentation have co-evolved. While marsupials are not placental mammals per se, they develop a non-invasive yolk-type placenta that, in the case of the opossum, is functional for a period of 3 days. The parental-conflict hypothesis proposes that paternal imprinting evolved as a way to enhance fetal growth, and maternal imprinting evolved as a way to control fetal growth. The hypothesis is supported by uniparental pregnancies, direct experimental evidence from null knockout mice, as well as human conditions associated with aberrant imprinting, all of which indicate that dysregulation of imprinted genes have a drastic effect on placental morphology and function. Thus, the evolutionary and experimental evidence supporting the co-evolution of placental function and imprinting reinforces the importance of concentrating on this family of genes when searching for candidate genes capable of affecting placental efficiency and fetal growth. This is important not only for human disorders such as intrauterine growth restriction and pre-eclampsia but also to elucidate the placental abnormalities commonly seen in somatic cell nuclear transfer clones of certain species, and to understand their impact upon litter size in species such as swine. As the placenta is one of the most divergent organs among placental mammals (ranging from highly invasive haemochorial to non-invasive epitheliochorial), we have utilized comparative genomics to better understand the role of imprinted genes in placental function. We have elected to focus our efforts on the non-invasive porcine placenta and have undertaken a systematic approach to identify and compare the family of imprinted genes in this species. Pregnancies generated from embryos derived from only maternal DNA (gynogenotes or parthenotes) produce small fetuses and placentas; in contrast, pregnancies generated with only paternal DNA (androge-notes) have large, overgrown placentas but only vestigial fetuses. As such, we conducted transcriptional profiling experiments of day 30 control and parthenogenetic porcine embryos using Affymetrix Porcine GeneChip microarrays. Four tissues were profiled: brain, fibroblast, liver, and placenta. At q< 0.05, we identified 13 known imprinted genes differentially expressed in at least one of the four tissue types: DCN, DIRAS3, IGF2, MEST, NDN, NNAT, PEG3, PEG10, PHLDA2, PLAGL1, SGCE, SLC38A4, and SNRPN. DIRAS3 was detected as differentially expressed in all tissues except placenta, MEST and SGCE in all tissues except liver, and IGF2 (known to be imprinted in swine) in all tissues except brain. NNAT was detected as differentially expressed only in brain and fibroblast. NDN, PEG10, PLAGL1, and SNRPN were detected as differentially expressed in all four tissues. To confirm the expression analysis results we followed up our screen for epigenetic asymmetry by interrogating the imprinting status of a subset of differentially expressed genes by pyrosequencing using an interbreed model. Our data also supports the lack of imprinting of GABRA5 and GNAS. These findings point to the usefulness of comparative models to clarify the tissue-specific epigenetic asymmetry of mammalian imprinted loci. This research was supported by USDA-CSREES grant 524383, and NIH grant HD048510 to JP and by a NSF Graduate Research Fellowship to ST. This work was performed as part of an initiative from the Center for Comparative Medicine and Translational Research (CCMTR) at the North Carolina State University College of Veterinary Medicine.

The 2007 Genetics Society of America Medal

THE recipient of the 2007 Genetics Society of America Medal is Shirley Tilghman. Shirley has made major scientific contributions to our understanding of gene expression and the epigenetic phenomenon of imprinting, but she has also been a national leader on matters of science policy and education.

Genomic Imprinting—The Story of the Other Half and the Conflicts of Silencing

Genomic imprinting is an epigenetic mechanism that produces functional differences between the paternal and maternal genomes and plays an essential role in mammalian development and growth. There are a number of genes in our genomes that are subject to genomic imprinting where one parent's copy of the gene is expressed while the other is silent. Silencing of one allele predetermines that any function ascribed to that gene are now dependant on the single active copy. Possession of only a single active allele can lead to deleterious health consequences in humans. If imprinted genes are crucial in mammalian development, one would also expect mutations in these genes to cause diseases. Since imprinting is an epigenetic mechanism, mistakes in maintaining epigenetic mark also cause imprinting disorders. Here we in this review focus on the current understanding of this unique genetic mechanism more than two decades after the first description of the imprinting phenomenon was given by McGrath and Solter. Although the possible molecular mechanisms by which imprinting is imposed and maintained are being identified, we have a long way to go in understanding the molecular mechanisms that regulate the expression of these oddly behaving genes, the function of imprinting and the evolution. Post genomic technologies might ultimately lead to a better understanding of the ‘imprinting effects’.

Normal development and neoplasia: the imprinting connection.

The observation that a number of autosomal genes are expressed in a parent of origin-dependent monoallelic manner has fuelled a frantic research effort into the underlying mechanisms and biological functions of this phenomenon, termed genomic or parental imprinting. The level of intrigue associated with this subject has been heightened by the discovery that the "transcriptional phenotype" of some imprinted genes shows developmental and tissue-specific variation, and that some imprinted genes are expressed biallelically in tumors. Here we describe some further examples of variation in the allele-specific transcription of an imprinted gene, human IGF2. Analysis of different sub-clones of an established tumor cell line (Jeg-3) revealed examples of both a switch from monoallelic to biallelic expression, as well as monoallelic expression from the opposite parental allele. Examination of IGF2 expression in adult human liver clearly demonstrated that the functional imprinting is manifested in a promoter-specific manner. The P1 promoter produced biallelically derived transcripts, whereas the remaining three promoters were utilized in a complex pattern of mono- and biallelic expression which varied from sample to sample. These observations emphasize the need to re-examine the imprinting phenomenon and its plasticity in terms of the cis elements and trans-acting factors involved in the transcriptional regulation of these genes both in the normal and pathological contexts.

IMPROVEMENT IN NON-DESTRUCTIVE READOUT RELIABILITY OF FERAM WITH ASYMMETRICAL PROGRAMMING

ABSTRACT A nondestructive readout (NDRO) scheme without polarization reversal in a ferroelectric random access memory (FeRAM) is proposed as a solution for extending the number of readout cycles. However, the readout signal in an NDRO FeRAM is so small that the NDRO operation is sensitive to deformation of the P−V hysteresis loop, which is a manifestation of imprint phenomena. In order to minimize the imprint effect in the NDRO FeRAM, we introduced an asymmetrical polarization programming scheme. Using this scheme, we can expect an extended number of readout cycles more than 1016 regardless of the imprint phenomena in ferroelectric capacitors.

Piezoelectric properties of Bi 4Ti 3O 12 thin films annealed in different atmospheres

Bismuth titanate (Bi 4Ti 3O 12—BIT) films were evaluated for use as lead-free piezoelectric thin-films in micro-electromechanical systems. The films were grown by the polymeric precursor method on Pt/Ti/SiO 2/Si (1 0 0) (Pt) bottom electrodes at 700 °C for 2 h in static air and oxygen atmospheres. The domain structure was investigated by piezoresponse force microscopy (PFM). Annealing in static air leads to better ferroelectric properties, higher remanent polarization, lower drive voltages and higher piezoelectric coefficient. On the other hand, oxygen atmosphere favors the imprint phenomenon and reduces the piezoelectric coefficient dramatically. Impedance data, represented by means of Nyquist diagrams, show a dramatic increase in the resistivity for the films annealed in static air atmopshere.

Simulating a perpendicular exchange-biased structure with a partially covering nonmagnetic insertion at the FM/AFM interface

Abstract The existence of minority spins, opposite to the perpendicular exchange bias, and majority spins aligned with this bias, and the dependence of the perpendicular exchange-bias field on the imprint effect, caused by the partially covering spacer at the ferromagnetic/antiferromagnetic (FM/AFM) interface, have been studied using Ising-type simulations. The present investigation suggests that the main factors influencing this phenomenon were dependent on the FM/AFM interface morphology, the balance between FM/AFM coupling and the FM-spins coupling, and the numerical balance between minority and majority spins. It was also determined that the imprint phenomenon can be used to enhance the perpendicular exchange-bias for small partial insertions at the FM/AFM interface.

Maaike van der Lugt, Le ver, le démon et la vierge: les théories médiévales de la génération extraordinaire: une étude sur les rapports entre théologie, philosophie naturelle et médecine, Collection L'Âne d'or, Paris, Les Belles Lettres, 2004, pp. xiv, 621, €37 (paperback 2-251-42018-5).

The worm, an animal formed by spontaneous generation, represents the Virgin Birth of Christ (“I am a worm and no man” of Psalm 22 could be read as a Christological text); the demon is a semi-spiritual creature capable of inseminating a woman; and the virgin, who gives birth parthenogenetically, is also, perhaps, the Virgin Mary. Maaike van der Lugt explores these three themes in medieval embryology through theological, philosophical, and medical texts from the eleventh to the fourteenth centuries. The introductory remarks on the Malleus maleficarum are something of a false trail; van der Lugt's focus is on scholastic accounts of human and animal generation in the Middle Ages, with a few excursions into more general texts. Van der Lugt convincingly argues that theologians, philosophers and physicians shared a discourse on development in which the Virgin Birth was a common theme. “Divine embryology” was concerned with four aspects of the Virgin Birth: the roles of Mary and the Holy Spirit, the influence of the stars, the timing of the formation of the embryo and its ensoulment, and the source of material from which it was formed. Scholastics made no absolute distinction between nature and miracle, and described the conception and Virgin Birth of Christ in the same terms as ordinary generation. The popular devotion to Maria Gravida also implied a real rather than a miraculous pregnancy: conception by the Holy Ghost was one more way, in addition to parthenogenesis, putrefaction and demonic insemination, by which a virgin could become pregnant. Van der Lugt then considers the limits of natural generation. Animals could become pregnant without insemination through the action of the wind (by proxy for the pneuma of semen) or the stars, though wind eggs and molar pregnancies were the imperfect results. Spontaneous generation yielded ignoble animals such as insects and vermin, though a search for nobler examples is suggested by medieval legends of barnacle geese, and vegetable lambs, which grew on trees. Medieval scholars accepted the possibility of conception by demons but, unlike later theologians, did not associate it with sorcery, and denied demons generative power, insisting on their borrowing or altering human semen to achieve offspring. Van der Lugt painstakingly compares French and English manuscript and printed sources on demonic reproduction: Merlin, who lacked a human father, is our conductor through a series of accounts of generation by incubi, succubi, and humans; parallels that made it easier to accept the Virgin Birth as a natural rather than a supernatural event. The chapters on the conception of Christ demonstrate that theologians drew on medical writings, some no longer extant, to describe the development of Christ in utero. Aristotelian embryology, via Arab translations, maintained that the mother provided the substance, not the form, of the embryo. If Christ, as the Nicene Creed stated, “took flesh” of the Virgin but nothing more, then her contribution, as Thomas Aquinas wrote, was no different from that of any other mother. The Franciscan view, articulated by John Duns Scotus, that Mary played an active role in the incarnation, was never accepted as orthodox, though the phenomenon of maternal imprinting—the formation of a foetus in the image of the mother's imagination—seemed to offer a means. One might speculate that the rejection of a formative maternal contribution to the foetus was due in part to theological arguments against a co-redemptrix. Van der Lugt does not address the wider theological issues or the “social or psychological dimension” of embryological theories. The presentation of primary material, much of it translated for the first time, is the book's strength, making it the most comprehensive account of medieval embryology available. Though the book's narrow focus necessarily leaves some peripheral areas, such as monstrous births and animal/human hybrids, unexplored, the re-establishment of theological embryology as a central theme is illuminating.