Exchange-bias phenomenon: the role of the ferromagnetic spin structure.

The exchange bias of antiferromagnetic-ferromagnetic (AFM-FM) bilayers is found to be strongly dependent on the ferromagnetic spin configuration. The widely accepted inverse proportionality of the exchange bias field with the ferromagnetic thickness is broken in FM layers thinner than the FM correlation length. Moreover, an anomalous thermal dependence of both exchange bias field and coercivity is also found. A model based on springlike domain walls parallel to the AFM-FM interface quantitatively accounts for the experimental results and, in particular, for the deviation from the inverse proportionality law. These results reveal the active role the ferromagnetic spin structure plays in AFM-FM hybrids which leads to a new paradigm of the exchange bias phenomenon.

Localization of an autosomal dominant retinitis pigmentosa gene to chromosome 7q.

Retinitis pigmentosa is a group of clinically and genetically heterogeneous retinopathies and a significant cause of worldwide visual handicap. We have typed DNA from members of a Spanish family segregating an autosomal dominant form of retinitis pigmentosa (adRP) using a large series of simple sequence polymorphic markers. Positive two-point lod scores have been obtained with fifteen markers including D7S480 (theta max = 0.00, Zmax = 7.22). Multipoint analyses using a subset of these markers gave a lod score of 7.51 maximizing at D7S480. These data provide definitive evidence for the localisation of an adRP gene on chromosome 7q, and highlight the extensive genetic heterogeneity that exists in the autosomal dominant form of this disease.

A 356-Kb sequence of the subtelomeric part of the MHC Class I region.

The subtelomeric part of the MHC Class I region contains 11 of the 21 genes described on chromosome 6 at position 6p21.3. The general organization of those and other genes resident in the region was revealed by determining a 356,376 bp sequence. Potential exons for new genes were identified by computer analysis and a large number of ESTs were selected by testing the sequence by the BLAST algorithm against the GenBank nonredundant and EST databases. Most of the ESTs are clustered in two regions. In contrast, the whole HLA-gene region is crammed with LINE and SINE repeats, fragments of genes and microsatellites, which tends to hinder the identification of new genes.

Is psychometric scoring of the McNew Quality of Life after Myocardial Infarction questionnaire superior to the clinimetric scoring? A comparison of the two approaches.

OBJECTIVE: 'Clinimetric' and 'psychometric' approaches are currently used to develop health related quality of life questionnaires. The Quality of Life after Myocardial Infarction questionnaire (QLMI) was originally developed using 'clinimetric' criteria; it was subsequently modified (McNew QLMI) and a new domain structure was defined using factor analysis. The objective of this study was to compare the measurement properties of the McNew QLMI scores when both approaches for scoring are used. METHODS: The McNew QLMI and SF-36 were administered to patients 2 weeks and 2 months after myocardial infarction. Two sets of scores for the McNew QLMI were computed using the original 'clinimetric' and the subsequent 'psychometrically' derived scoring systems. Reliability statistics for the two sets of domains were compared and construct validity was assessed by establishing a priori hypotheses on the expected correlation between each score and the dimensions of the SF-36. RESULTS: Both sets of scores had similar reliability (Cronbach's alpha between 0.64 and 0.93) and responsiveness (SRMs between 0.17 and 0.87) while validity was better for the 'clinimetric' set of scores (concordance between observed and expected correlations was moderate for the 'clinimetric' scores and fair for the 'psychometric' scores). CONCLUSION: Since overall measurement properties of the 'clinimetrically' scored McNew QLMI are better than the 'psychometrically' scored version, we suggest that either the original 'clinimetric' system is used or that an improved 'psychometric' version is developed.

The Drosophila SOX-domain protein Dichaete is required for the development of the central nervous system midline.

SOX-domain proteins are a class of developmentally important transcriptional regulators related to the mammalian testis determining factor SRY. In common with other SOX-domain genes, the Drosophila Dichaete gene has a dynamic expression profile in the developing central nervous system, including cells of the ventral midline. We find defects in the differentiation of midline glia and concomitant axonal defects in Dichaete mutants that are rescued by driving Dichaete expression in the midline. Since Dichaete is required for the correct specification or differentiation of midline glia, we have used the ventral midline as a model system to study SOX gene function in vivo and demonstrate a genetic interaction between Dichaete and the POU domain gene ventral veinless. In mammals, a protein related to Dichaete, SOX2, also interacts with POU transcription factors. The midline phenotypes of Dichaete mutations are rescued by expression of mouse SOX2. Our data suggest that SOX gene structure, function and interactions have been conserved during evolution.

Regulatory mutations of the Drosophila Sox gene Dichaete reveal new functions in embryonic brain and hindgut development.

Sox domain proteins encompass a conserved family of transcriptional regulators that are implicated in a variety of developmental processes in eukaryotes from worm to man. The Dichaete gene of Drosophila encodes a group B Sox protein related to mammalian Sox1, -2, and -3 and, like these proteins, it is widely and dynamically expressed throughout embryogenesis. In order to unravel new Dichaete functions, we characterized the organization of the Dichaete gene using a combination of regulatory mutant alleles and reporter gene constructs. Dichaete expression is tightly controlled during embryonic development by a complex of regulatory elements distributed over 25 kb downstream and 3 kb upstream of the transcription unit. A series of regulatory alleles which affect tissue-specific domains of Dichaete were used to demonstrate that Dichaete has functions in addition to those during segmentation and midline development previously described. First, Dichaete has functions in the developing brain. A specific group of neural cells in the tritocerebrum fails to develop correctly in the absence of Dichaete, as revealed by reduced expression of labial, zfh-2, wingless, and engrailed. Second, Dichaete is required for the correct differentiation of the hindgut. The Dichaete requirement in hindgut morphogenesis is, in part, via regulation of dpp, since ectopically supplied dpp can rescue Dichaete phenotypes in the hindgut. Taken together, there are now four distinct in vivo functions described for Dichaete that can be used as models for context-dependent comparative studies of Sox function.

[Bladder endometriosis simulating a bladder tumor]. / Endometriosis vesical simulando un tumor vesical.

Endometriosis is relatively frequent in females of menstrual age and consists in the appearance of active endometrial tissue at sites other than the uterine cavity (genital system or adjacent organs). Endometrial tissue has been described to colonize the urinary system, particularly the urinary bladder. The most common clinical features of vesical endometriosis are urgency and frequency, hypogastric pain and hematuria. We report on a case of vesical endometriosis whose presenting features were urgency and urinary incontinence. The urological work up disclosed a solid vesical mass. Cystoscopy was highly suggestive of endometrial submucosa formation which was confirmed by TUR.

[Hepatic markers (Ac-HVA-IgM and AcHBc-IgM) in cases of infectious hepatitis in Dominican children]. / Marcadores hepáticos (Ac-HVA-IgM y AcHBc-IgM) en casos de hepatitis infecciosas en niños dominicanos.

The presence of IgM antibodies for the HVA and HBc antigens in 90 children of 15 or less years with acute hepatitis were investigated, finding that 62% (58) were positive for HVA, 8.9% (8) for HBc and 27.8% (25) did not show antibodies for HVA or HBc (non-A non-B hepatitis); comments are made on some clinical and epidemiological findings such as a higher frequency of blood transfusions in HNANB, more males in HB and HNANB, and more hepatomegaly and liver sensitivity in HNANB.

Autosomal dominant retinitis pigmentosa (adRP): exclusion of a gene from three mapped loci provides evidence for the existence of a fourth locus.

Retinitis Pigmentosa (RP) is a group of inherited retinopathies which affect approximately 1 in 4,000 individuals. The disorder can be classified on the basis of inheritance; dominant, recessive and X-linked forms have been well documented. The existence of genetic heterogeneity within autosomal dominant RP (adRP) had been previously demonstrated. As a result of extensive linkage studies in 2 large Irish families and 1 American pedigree three adRP genes have been mapped. adRP genes have been localised to chromosome 3q close to the rod photoreceptor gene, rhodopsin; to chromosome 6p close to another transmembrane photoreceptor gene, peripherin/RDS and to the pericentric region of chromosome 8, although the causative gene in this region has not yet been identified. Here we report the results of a linkage study in a Spanish family, who exhibit an early-onset form of adRP. The adRP gene segregating in this family has been excluded from the three known adRP loci on chromosomes 3q, 6p and 8 using a series of both intragenic microsatellite markers from the rhodopsin and peripherin/RDS genes and markers flanking the three known loci. These results provide definitive evidence for the existence of a fourth adRP locus, further emphasising the genetic heterogeneity that exists within adRP.

The Dichaete gene of Drosophila melanogaster encodes a SOX-domain protein required for embryonic segmentation.

We have cloned and characterised a member of the High Mobility Group superfamily of genes from Drosophila, Sox70D, which is closely related to the mammalian testis determining gene SRY. Sox70D corresponds to the dominant wing mutation Dichaete. Homozygous deletions of the Sox70D gene and recessive lethal Dichaete alleles have a variable embryonic segmentation phenotype. Dichaete is expressed in early embryos in a dynamic pattern reminiscent of gap and pair-rule genes and is required for the appropriate expression of the primary pair-rule genes even skipped, hairy and runt. The molecular nature of Dichaete and its expression pattern during early embryogenesis suggest that the gene plays a key role in early development; the variability in both the segmentation phenotype and the effects on pair-rule gene expression suggests that this role is to support the transcriptional regulation of key developmental genes rather than directly regulate any one of them.

Identification of 96 single nucleotide polymorphisms in eight genes involved in iron metabolism: efficiency of bioinformatic extraction compared with a systematic sequencing approach.

Single nucleotide polymorphisms (SNPs) can significantly contribute to the characterization of the genes predisposing to iron overloads or deficiencies. We report an SNP survey of coding and non-coding regions of eight genes involved in iron metabolism, by two successive methods. First, we made use of the public domain sequence data, by using assembled expressed sequence tags, non-redundant sequences, and SNP database screening. We extracted 77 potential SNPs of which only 31 could be further validated by sequencing DNA from 44 unrelated multi-ethnic individuals. Our results indicate that a bioinformatic approach may be effective only in those cases where candidate SNPs are extracted from two different data sources or in cases of experimentally confirmed SNPs. Second, additional systematic sequencing of DNA from 24 unrelated Breton subjects increased the number of SNPs over a total length of 86 kb to 96. The average distance between the SNPs and minor allele frequencies were higher than reported by others authors; this discrepancy may reflect the nature of the genes studied and the ethnic homogeneity of our test population.