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At least 1,063 records · Page 59Linked to original sources

PubMed2002

Appearance-based segmentation of medial temporal lobe structures.

A new paradigm for the characterization of structure appearance is proposed, based on a combination of gray-level MRI intensity data and a shape descriptor derived from a priori principal components analysis of 3D deformation vector fields. Generated without external intervention, it extends into 3D more classic, 2D manual landmark-based shape models. Application of this novel concept led to a method for the segmentation of medial temporal lobe structures from brain magnetic resonance images. The strategy employed for segmentation aims at synthesizing, using the appearance model, a deformation field that maps a new volume onto a reference target. Any information defined on the reference can then be propagated back on the new volume instance, thereby achieving segmentation. The proposed method was tested on a data set of 80 normal subjects and compared against manual segmentation as well as automated segmentation results from ANIMAL, a nonlinear registration and segmentation technique. Experimental results demonstrated the robustness and flexibility of the new method. Segmentation accuracy, measured by overlap statistics, is marginally lower (< 2%) than ANIMAL, while processing time is six times faster. Finally, the applicability of this concept toward shape deformation analysis is presented.

Algorithms↗

PubMedDate not supplied

Reliability testing of a new scar assessment tool, Matching Assessment of Scars and Photographs (MAPS).

A new scar-assessment tool, the Matching Assessment of Scars and Photographs (MAPS), which uses a set of reference photographs, a numeric scale, and location technique, was tested for its reliability in two stages. First, using five adults, three raters assessed 32 burns scars twice within 3 days. Subsequently, reliability was tested during a 6-month time frame, emphasizing the process of localizing test areas as scars changed and raters forgot the previous assessment. Three raters, from a pool of five, each made three assessments on 29 scars in seven subjects, on average 8 weeks apart. Inter-rater reliability was tested, using Kendall's Tau C and intraclass correlations, respectively, for stages 1 and 2. Agreement was good for border height (0.63-0.70 and 0.78), moderate to good for thickness (0.60-0.74 and 0.81), and good for color (0.55-0.71 and 0.79), whereas for surface it was fair (0.25-0.38 and 0.40). The localization technique was reliable (accuracy within 3 mm) in 93% to 96% of recordings. The MAPS tool is considered ready for clinical use.

Burns↗

PubMed2002

Construction and analysis of a human-chimpanzee comparative clone map.

The recently released human genome sequences provide us with reference data to conduct comparative genomic research on primates, which will be important to understand what genetic information makes us human. Here we present a first-generation human-chimpanzee comparative genome map and its initial analysis. The map was constructed through paired alignment of 77,461 chimpanzee bacterial artificial chromosome end sequences with publicly available human genome sequences. We detected candidate positions, including two clusters on human chromosome 21 that suggest large, nonrandom regions of difference between the two genomes.

Animals↗

PubMed1997

Characterization of multicopy suppressor genes that complement a defect in the Wis1-Sty1 MAP kinase cascade involved in stress responses in Schizosaccharomyces pombe.

The Wis1-Sty1 mitogen-activated protein (MAP) kinase cascade is one of the major signaling systems involved in a wide range of stress responses in Schizosaccharomyces pombe. It is known that Deltawis1 and Deltasty1 mutants exhibit highly pleiotropic phenotypes, including a phenotype of temperature sensitivity for growth. In this study, we screened multicopy suppressor genes that allow both the Deltawis1 and Deltasty1 mutants to grow simultaneously at a non-permissive temperature, 37 degrees C. Two such multicopy suppressors were cloned and characterized as sds23(+) and hxk2(+) genes. The former is known to specify a protein that functions as a multicopy suppressor for mutations of the PP1 protein phosphatase and the 20S cyclosome/anaphase-promoting complex (APC), and the latter encodes hexokinase 2. It was revealed that the multicopy sds231 gene restored a defect in the mating efficiency caused by the Deltawis1 and Deltasty1 mutations, whereas the multicopy hxk2(+) gene suppressed a phenotype of heat-shock sensitivity for growth of these mutant cells. These findings are discussed with special reference to the Wis1-Sty1 MAP kinase signaling pathway in S. pombe.

Journal Article↗

PubMed2004

Percutaneous epicardial mapping during ablation of difficult accessory pathways as an alternative to cardiac surgery.

OBJECTIVES: The aim of this study was to define the role of percutaneous epicardial mapping for the ablation of previous failed ablation of accessory pathways. BACKGROUND: Cardiac surgery is the only curative option for failed radiofrequency (RF) catheter ablation of accessory pathway (AP)-mediated tachycardias. We investigated a combined percutaneous epicardial and endocardial approach for failed AP ablations. METHODS: We present our experience in a series of 6 cases (7 APs) with previous failed attempts at catheter ablation (median 2 attempts, range 1-4) and persistent symptomatic tachycardias. Endocardial mapping of the APs was performed using conventional techniques. Sites with local electrograms suggestive of AP location were selected. When initial endocardial mapping was not successful for ablation of the pathway, percutaneous transthoracic pericardial puncture was performed via a subxiphoid approach, and an ablation catheter was positioned at the epicardial aspect of the putative AP location for epicardial-endocardial electrogram comparison. Endocardial RF energy was applied to locations considered appropriate. Epicardial RF applications were delivered when endocardial applications failed. Coronary arteriography was performed to assess the proximity of coronary arteries to the ablation catheter. RESULTS: APs were located in the right free wall (4 patients, 5 APs) and the right (1 patient) and left (1 patient) posteroseptal regions. In all patients, epicardial mapping assisted in identifying successful ablation sites. In 3 patients, the earliest atrial activation during orthodromic tachycardia was present in an epicardial electrogram. Successful AP ablation was achieved with an epicardial RF application in 2 patients, either alone or with simultaneous endocardial-epicardial delivery. In the remaining 4 patients, APs were successfully ablated endocardially after epicardial mapping. These patients represent 18% of all cases referred to our institution for ablation of previously failed accessory pathways (6/32 patients). CONCLUSIONS: A combined endocardial-epicardial approach to mapping and RF ablation can facilitate successful endocardial ablation in most cases. In selected cases, APs can be ablated by epicardial delivery of RF. Epicardial mapping is an effective alternative to cardiac surgery for patients in whom prior attempts at AP ablation have failed.

Adolescent↗

PubMed1993

Genetic mapping of dinucleotide repeat polymorphisms and von Hippel-Lindau disease on chromosome 3p25-26.

A genetic map of highly polymorphic microsatellite markers spanning the von Hippel-Lindau region (VHL) of 3p25 was constructed using the CEPH reference pedigrees. A greater than 1000:1 odds map of pter-D3S1038-RAF1-D3S651-D3S656-D3S110- D3S1255-cen was found. Genotyping of six multigenerational VHL families showed the region surrounding the D3S1038 marker to be the most likely location for the VHL gene with a peak location score of 10.04 with VHL completely linked to D3S1038. These data provide an initial high resolution genetic map of this region; D3S1038 appears to be a highly polymorphic marker that should prove useful in the future for presymptomatic diagnosis.

Adult↗

PubMed2000

Signal-averaged isoharmonic body surface maps of patients with ischemic cardiomyopathy.

INTRODUCTION: Prevention of sudden arrhythmic cardiac death depends on accurate identification of individuals at high risk. Previous studies of signals recorded directly from arrhythmogenic tissue suggested that the predictive value of the signal-averaged ECG could be enhanced by expanded temporal, spectral, and spatial analysis. Accordingly, we performed a prospective study of 192-lead signal-averaged body surface maps from 43 patients with ischemic cardiomyopathy referred for electrophysiologic study. Three groups were included: 15 patients with clinical ventricular tachycardia (VT), 12 patients with inducible VT, and 16 patients with non-VT. METHODS AND RESULTS: The patients were well matched with regard to age, gender, infarct location, ejection fraction (28% +/- 9%), QRS duration, and incidence of nonsustained VT (96%). Isoharmonic maps of the entire cardiac cycle were constructed for each patient. The peaks of the 1-7 Hz isoharmonic maps distinguished patients with clinical VT from non-VT and inducible VT patients (1,152 +/- 273, 852 +/- 283, and 808 +/- 272, respectively; P = 0.003). After prospective observation for 22 +/- 16 months, the combined endpoint of spontaneous sustained VT, ventricular fibrillation, appropriate defibrillator therapy, and death was predicted by inducibility of VT (relative risk 3.8, P = 0.008) and by the signal-averaged isoharmonic body surface map (relative risk 3.1, P = 0.02). CONCLUSION: These results confirm the diagnostic utility of signal-averaged isoharmonic body surface maps in a rigorously defined patient population.

Aged↗

PubMed1993

The GDB Human Genome Data Base: a source of integrated genetic mapping and disease data.

The GDB Human Genome Data Base refers collectively to GDB and OMIM, Online Mendelian Inheritance in Man. GDB and OMIM are linked databases that provide an international repository for information generated by the Human Genome Initiative. GDB contains human gene mapping data, while OMIM offers the text of Dr. Victor A. McKusick's catalog of genetic disease and phenotype descriptions. These databases, updated and edited continuously, integrate bibliographic and full-text information with several types of mapping data. They are accessible through a flexible interface and are available through SprintNet and the Internet to the scientific community without cost. This paper provides an overview of the context, development, structure, content, and use of these databases.

Chromosome Mapping↗

PubMed1992

Restriction fragment length polymorphisms near the islet amyloid polypeptide gene in Japanese subjects.

Two restriction fragment length polymorphisms (RFLPs) near the human islet amyloid polypeptide (IAPP) gene were examined in 50 Japanese patients with non-insulin-independent diabetes mellitus (NIDDM) and 54 non-diabetic controls. RFLPs were identified with the enzymes PvuII (A1 = 21 kb and A2 = 18 kb) and BglII (B1 = 9 kb and B2 = 7 kb). These RFLPs were in complete linkage disequilibrium with A1 which was in disequilibrium with B2, as was A2 with B1. Since these two RFLPs map to different locations in the 5'-flanking region of the IAPP gene, they are most likely due to changes in the sequence of the sites recognized by PvuII and BglII rather than to an insertion/deletion-type DNA polymorphism. There were no differences in the genotypic or allelic frequencies of these RFLPs between Japanese subjects with NIDDM and non-diabetic controls implying that these RFLPs do not play a major role in the development of NIDDM in this population.

Adult↗

PubMed1992

Linkage map of eight human chromosome 11q markers, including DRD2, spanning 60 cM.

We have constructed a linkage map of eight RFLP markers located on chromosome 11q in the region of the dopamine D2 receptor gene (DRD2) recognized by probe hD2G1. Abnormalities in dopaminergic neurotransmission mediated by this receptor have been implicated in several psychiatric disorders. The map was generated using six large reference families (from 294 to 419 individuals per locus), which are largely independent of the CEPH families, primarily using the LINKMAP and ILINK programs of the LINKAGE package of Lathrop and Lalouel. The most likely order and recombination frequencies are: [sequence: see text] The relative order of D11S84-STMY, DRD2-D11S29, and D11S146-INT2 could not be resolved reliably. There were no significant sex differences in recombination frequency. We introduce here a version of LINKMAP adapted to run under distributed parallel processing (LINDA-LINKMAP). Using pairwise analyses, we have also placed D11S421 proximal to this group.

Chromosome Mapping↗

PubMedDate not supplied

Growth tracks in dental enamel.

The present paper evaluates the enamel growth tracks as tools in the chronological mapping of dental development, with special reference to hominids. Dental enamel consists of tightly packed hydroxyapatite crystals organized by differential orientation into a pattern of prisms and interprisms. The crystal organization is probably under the influence of both cellular and physico-chemical factors. The structure of mature enamel testifies to events that took place during enamel formation. The prisms are the fossilized tracks traced out by ameloblasts. The tangential diameter of ameloblasts and the central distance of prisms increase from the enamel-dentine junction to the enamel surface. Available evidence suggests that prism cross-striations are light microscopic expressions of prism varicosities and/or compositional variations, that these are due to a rhythm in enamel formation, and that this rhythm is diurnal. In human enamel the mean daily rate of enamel production is about 3.5 micron, but increases from inner to outer enamel and decreases from incisal/cuspal to cervical enamel. Conclusive evidence has shown that Retzius lines are incremental lines. Evenly spaced Retzius lines probably represent a 6-11 day rhythm in enamel formation, while other Retzius lines may be due to various types of stress. The geometry of the enamel growth tracks and their chronological significance are valuable tools in chronological mapping of dental development and for understanding temporal and spatial patterns in tooth morphogenesis. The taxonomic significance of prism packing patterns, prism decussation and enamel thickness should be clarified through further systematic descriptive research.

Ameloblasts↗

PubMed1990

Molecular analysis of human acatalasemia. Identification of a splicing mutation.

To search for the molecular defect of Japanese-type acatalasemia, we cloned the mutant catalase gene from a person with this deficiency. The nucleotide sequence of the mutant gene was determined for all exons, exon/intron junctions, and 5' and 3' flanking regions, and the findings were compared with the sequence from the normal gene. Seven base differences were found between the two genes. Among them, a G to A substitution at the fifth position of intron 4 (a splicing mutation) seemed most likely to be responsible for the defective catalase synthesis in the subject. To obtain suggestive evidence, we constructed chimeric genes that contained a segment of either the normal or mutant catalase gene, encompassing a 3' part of exon 4, the entire intron 4 and a 5' portion of exon 5, within the third exon of the human alpha-globin gene. When this chimeric gene construct was introduced into simian virus 40-transformed simian cells (COS-7), the transcript of the normal catalase/alpha-globin chimeric gene was spliced correctly, as revealed by Northern blotting and RNase mapping techniques. In contrast, the splicing of the mutant chimeric pre-mRNA occurred between the 5' donor site of the preceding intron and the 3' acceptor site of the intron containing the substitution, thereby skipping one entire exon sequence. Thus, the G to A transition at the fifth position of intron 4 of the catalase gene indeed severely limits the correct splicing of the RNA product. The same splice site mutation was found in the genomic DNA of another acatalasemic individual from an unrelated family. We suggest that this base substitution is the causal mutation of these cases of Japanese-type acatalasemia.

Acatalasia↗

PubMed2002

Fidelity and spatio-temporal control in MAP kinase (ERKs) signalling.

Extracellular signals transduced via receptor tyrosine kinases, G-protein-coupled receptors or integrins activate Ras, a key switch in cellular signalling. Although Ras can activate multiple downstream effectors (PI3K, Ral em leader ) one of the major activated pathway is a conserved sequential protein kinase cascade referred to as the mitogen activated protein (MAP) kinase module: Raf>MEK>ERK. The fidelity of signalling among protein kinases and the spatio-temporal activation are certainly key determinants for generating precise biological responses. The fidelity is ensured by scaffold proteins, a sort of protein kinase "insulators" and/or specific docking sites among the members of the signalling cascade. These docking sites are found in upstream and downstream regulators and MAPK substrates [Nat Cell Biol 2 2000 110]. The duration and the intensity of the response are in part controlled by the compartmentalisation of the signalling molecules. Growth factors promote nuclear accumulation and persistent activation of ERK (p42/p44 MAP kinases) during the entire G1 period with an extinction during S-phase. These features are exquisitely well controlled by (i) the temporal induction of the MAP kinase phosphatases, MKP1-3, and (ii) the compartmentalisation of the signalling molecules. We have shown that MKP1-2 induction is strictly controlled by the activation of the MAP kinase module providing evidence for an autoregulatory mechanism. This negative regulatory loop was further enhanced by the capacity of ERK to phosphorylate MKP1 and 2. This action reduced the degradation rate of these MKPs through the ubiquitin-proteasomal system [Science 286 1999 2514]. Whereas the two upstream kinases of the module, Raf and MEK remained cytoplasmic, ERK anchored to MEK in the cytoplasm of resting cells, rapidly translocated to the nucleus upon mitogenic stimulation. This process was rapid, reversible, and controlled by the strict activation of the MAPK cascade. Prevention of this nuclear translocation, by overexpression of a cytoplasmic ERK-docking molecule (inactive MKP3) prevented growth factor-stimulated DNA replication [EMBO J 18 1999 664]. Following long term stimulation, ERK progressively accumulated in the nucleus in an inactive form. This nuclear retention relied on the neosynthesis of short-lived nuclear anchoring proteins. Nuclear inactivation and sequestration was likely to be controlled by MAP kinase phosphatases 1 and 2. Therefore we propose that the nucleus represents a site for ERK action, sequestration and signal termination [J Cell Sci 114 2001 3433]. In addition, with the generation of mice invalidated for each of the ERK isoforms, we will illustrate that besides controlling cell proliferation the ERK cascade also controls cell differentiation and cell behaviour [Science 286 1999 1374].

Animals↗

PubMed1995

Genetic analysis of three loci homologous to human G9a: evidence for linkage of a class III gene with the chicken MHC.

The cDNA clones of two newly discovered genes in the class III region of the human major histocompatibility complex (MHC) were hybridized to chicken DNA. One of these cDNA clones (pG9a-4C7), which detects the single-copy human G9a (BAT8) gene, gave a repeatable restriction pattern. This heterologous cDNA clone was used to detect and map three different PstI restriction fragment length polymorphisms among the two internationally recognized chicken reference populations. Two of the loci were unlinked to previously mapped markers, but one polymorphism cosegregated with the EaB locus in the Compton mapping population. These results provide evidence that some genes of the mammalian class III region, such as G9a, may be linked to the MHC in chickens.

Animals↗

PubMed1997

A single bit RF domain complex cross-correlation velocity estimator for color flow mapping.

This paper evaluates the performance of a one bit mean frequency estimator to estimate blood flow velocity for ultrasound color flow mapping. This one bit mean frequency estimator, referred to as BC3 estimator, is derived from the recently introduced complex cross-correlation model (C3M) employing the full dynamic data range. The C3M velocity estimator is not suitable for application in color flow mapping because of its high hardware complexity and associated computational load. The BC3 estimator estimates the mean blood flow velocity using only two complex cross-correlation coefficients. For this purpose the latter are computed by means of a complex one bit cross-correlation operation. Each sample of the RF signals is converted into an one bit representation based on the sign of the real and imaginary part of the RF samples. A full derivation and mathematical description of the BC3 estimator is presented. In addition, a thorough performance evaluation of the BC3 estimator in comparison with the full dynamic range C3M velocity estimator is carried out by means of signal simulations to document the effect of signal to noise ratio, sample frequency and bandwidth. For the specific simulation conditions considered the standard deviation of both estimators (C3M and BC3) is comparable. The bias of the BC3 estimator appears to be a function of velocity, while the full dynamic range C3M velocity estimator exhibits no bias. The simulation results are confirmed by evaluation of data from an in vivo measurement. Taking into account the low hardware complexity and computational load in combination with the achieved precision, it may be concluded that the BC3 estimator is well suited for implementation in color flow mapping.

Blood Flow Velocity↗

PubMed2006

Molecular characterization, structure and developmental expression of Megane bHLH factor.

We report here the full-length sequence identification, molecular characterization, detailed demarcation expression analysis relevant to morphological marker genes and mapping of a bHLH transcription gene, referred to as Megane (Mgn). Mgn protein is structurally related to the neurogenic Drosophila hairy and Enhancer of split (h/E(spl)) proteins. The unique structural properties of Mgn factor in several characteristic residues define the gene as related to h/E(spl), but distinguish it from previously identified mammalian members of the family. Mgn is a single copy gene on mouse chromosome 8 and encodes a 27kDa protein that functions in the nucleus. First expression of Mgn is detected at mouse embryonic day 9.5 within the most rostral part of the cephalic flexure of the developing midbrain. Later, Mgn expression extends into other alar areas of the midbrain and forebrain, developmentally controlled in a regional specific pattern.

Amino Acid Sequence↗

PubMed1999

Persistent infection of bovine herpesvirus type 4 in bovine endothelial cell cultures.

Herpesviruses can establish a persistent infection in the cells and tissues of their natural hosts and thus may produce diseases due to cytolytic infections. We have isolated a herpesvirus from a bovine vascular endothelial cell culture after continuous subculturing. Typical cytopathic changes were observed in bovine endothelial cell cultures 2 days after inoculation of the virus. The virus had an icosahedral nucleocapsid of 100-150 nm in diameter and an envelope. The sequences of some DNA fragments of the virus were highly homologous to those of the bovine herpesvirus type 4 (BHV-4) strains. The DNA restriction maps of the virus and the reference strains of BHV-4, DN 599 and Movar 33/63 were very similar but not identical. Therefore, the newly isolated virus has been designated Taiwan strain. The presence of BHV-4 DNA in apparently normal bovine endothelial cell cultures was shown by Southern blot hybridization with the BamHI fragment of the newly isolated BHV-4 and was further confirmed by digestion of the DNA with BamHI plus AccI. In conclusion, we have demonstrated that BHV-4 persisted in the bovine endothelial cell cultures and continuous subcultures could lead to the production of infectious viral particles.

Animals↗

PubMed1991

Isolation of sequences that span the fragile X and identification of a fragile X-related CpG island.

Yeast artificial chromosomes (YACs) were obtained from a 550-kilobase region that contains three probes previously mapped as very close to the locus of the fragile X syndrome. These YACs spanned the fragile site in Xq27.3 as shown by fluorescent in situ hybridization. An internal 200-kilobase segment contained four chromosomal breakpoints generated by induction of fragile X expression. A single CpG island was identified in the cloned region between markers DXS463 and DXS465 that appears methylated in mentally retarded fragile X males, but not in nonexpressing male carriers of the mutation nor in normal males. This CpG island may indicate the presence of a gene involved in the clinical phenotype of the syndrome.

Base Sequence↗