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PubMed1991

Independent segregation of glutathione S-transferase and fatty acid ethyl ester synthase from pancreas and other human tissues.

Glutathione S-transferase (GST) isoenzymes of human pancreas were purified, characterized and evaluated for their possible role in the metabolism of ethanol. Human pancreas has at least two GST isoenzymes belonging to the Alpha class (pI 8.8 and 8.1), one belonging to the Mu class (pI 6.4) and one belonging to the Pi class (pI 4.9). During the purification of GSTs from pancreas as well as from heart, liver, lung, brain and muscle, the fatty acid ethyl ester synthase (FAEES) activity was monitored in order to evaluate the role of GSTs in metabolism of ethanol, as suggested in earlier studies. Both t.l.c. and h.p.l.c. were used to identify ethyl oleate in reaction mixtures to monitor FAEES activity. During the purification of GSTs with the use of affinity chromatography on GSH linked to epoxy-activated Sepharose 6B, FAEES and GST activities from each of these tissues segregated independently. Purified GST isoenzymes from these tissues did not exhibit any FAEES activity. Antibodies raised against Pi-class GST, as expected, immunoprecipitated most of the GST activity of brain and heart without precipitating FAEES activity. These results suggest that human GST isoenzymes belonging to the Alpha, Mu and Pi classes do not express FAEES activity. The independent segregation of GST and FAEES activities was further demonstrated by monitoring GST activity during the purification of FAEES from pancreas. It was found that purified FAEES had no GST activity towards 1-chloro-2,4-dinitrobenzene and a number of other electrophilic substrates. Results of these studies demonstrate that FAEES and GSTs are distinct proteins.

Acyltransferases↗
PubMed2001

The role of sequential stream segregation and frequency selectivity in the perception of simultaneous sentences by listeners with sensorineural hearing loss.

The purpose of this study was to determine the role of frequency selectivity and sequential stream segregation in the perception of simultaneous sentences by listeners with sensorineural hearing loss. Simultaneous sentence perception was tested in listeners with normal hearing and with sensorineural hearing loss using sentence pairs consisting of one sentence spoken by a male talker and one sentence spoken by a female talker. Listeners were asked to repeat both sentences and were scored on the number of words repeated correctly in each sentence. Separate scores were obtained for the first and second sentences repeated. Frequency selectivity was assessed using a notched-noise method in which thresholds for a 1,000 Hz pure-tone signal were measured in noise with spectral notch bandwidths of 0, 300, and 600 Hz. Sequential stream segregation was measured using tone sequences consisting of a fixed frequency (A) and a varying frequency tone (B). Tone sequences were presented in an ABA_ABA_... pattern starting at a frequency (B) either below or above the frequency of the fixed 1,000 Hz tone (A). Initially, the frequency difference was large and was gradually decreased until listeners indicated that they could no longer perceptually separate the two tones (fusion threshold). Scores for the first sentence repeated decreased significantly with increasing age. There was a strong relationship between fusion threshold and simultaneous sentence perception, which remained even after partialling out the effects of age. Smaller frequency differences at fusion thresholds were associated with higher sentence scores. There was no relationship between frequency selectivity and simultaneous sentence perception. Results suggest that the abilities to perceptually separate pitch patterns and separate sentences spoken simultaneously by different talkers are mediated by the same underlying perceptual and/or cognitive factors.

Adult↗
PubMed2003

Talker separation and sequential stream segregation in listeners with hearing loss: patterns associated with talker gender.

The purpose of this paper was to examine the relations between the ability to separate simultaneous sentences spoken by talkers of different gender and the ability to separate pitch patterns in a sequential stream segregation task. Simultaneous sentence pairs consisting of 1 sentence spoken by a male talker and 1 sentence spoken by a female talker were presented to 11 listeners with sensorineural hearing loss. Listeners were asked to repeat both sentences and were scored on the number of words repeated correctly. Separate scores were obtained for the male and female sentences. Sequential stream segregation was then measured using series of tones consisting of a fixed frequency (A) and a varying frequency tone (B). Tone series were presented in an ABA_ABA_... pattern starting at a varying frequency either below (ascending pattern) or above (descending pattern) the frequency of the fixed 1000 Hz tone. Fusion thresholds, defined as the frequency separation at which listeners could no longer perceptually separate the tones A and B, were obtained for both ascending and descending patterns. There was no significant difference between ascending and descending fusion thresholds based on the group data, but substantial individual differences were observed. Speech recognition scores for the male talker were strongly related to ascending fusion thresholds, but not descending thresholds. In contrast, speech recognition scores for the female talker were strongly related to the descending thresholds, but not the ascending thresholds. For both the male and female talkers, better recognition scores were associated with lower (nearer to normal) fusion thresholds. Results suggest that the importance of streaming in the perceptual separation of talkers may depend on the nature of the information provided by the changing pitch stream.

Aged↗
PubMed2002

CTLA-4 49 A/G dimorphism and type 1 diabetes susceptibility: a French case-control study and segregation analysis. Evidence of a maternal effect.

Several studies have demonstrated an association of cytotoxic T lymphocyte-associated molecule 4 (CTLA-4) (IDDM 12) alanine 17 with type 1 diabetes, but we wished to study the parental effect of CTLA-4 49 A/G dimorphism in diabetic families. The CTLA-4 exon 1 polymorphism (49 A/G), HLA-DRB1 and insulin gene (INS) variable number tandem repeats (VNTR) were analysed in 134 type 1 diabetic patients vs. 273 control subjects. The segregation analysis for transmission was carried out in 70 informative diabetic families using the transmission distortion test (TDT). All genotyping was performed by PCR-RFLP. CTLA-4 49 G allele frequency was not increased in diabetic patients compared to controls (41 vs. 38%, not significant). The distribution of GG, AG and AA CTLA-4 genotypes was similar in the two groups (13, 57 and 30% vs. 11, 54 and 35%, respectively) and was independent of HLA-DRB1 or INS VNTR polymorphism. The CTLA-4 49 G allele showed weak distorted transmission to the diabetic offspring, whereas random transmission was observed in unaffected offspring. This distortion is attributable to a maternal effect (71% compared to the 50% expected ratio; tdt = 4.8; P < 0.03). The combined transmission of maternal CTLA-4 G with HLA-DRB1*03 (90%; tdt = 6.4; P < 0.01) and VNTR class I (80%; tdt = 5.4; P < 0.02) enhanced the susceptibility effect of each marker separately. We noted a slight CTLA-4 49 G and HLA-DRB1*04 distortion of transmission shared in paternal and maternal diabetic meiosis. In non-diabetic offspring, the CTLA-4 49 A allele confers a protective effect in the presence of maternal HLA-DRB1*03 and paternal HLA-DRB1*04 alleles. Despite the absence of a positive association of the CTLA-4 49 G allele with type 1 diabetes, our segregation analysis supports the hypothesis of a modulation by CTLA-4 49 G/A dimorphism of the susceptibility conferred by maternal HLA-DRB1*03 inheritance. This potential parental effect needs to be confirmed in a larger data set.

Adenine↗
PubMed1999

The native virulence plasmid combination affects the segregational stability of a theta-replicating shuttle vector in Bacillus anthracis var. New Hampshire.

The segregational stability of a small, theta-replicating, non-mobilizable shuttle plasmid (pAEX-5E) was determined in fully virulent (pX01+/pX02+), partially cured (pX01+/pX02- and pX01-/pX02+) and fully cured (pX01-/pX02-) derivatives of Bacillus anthracis var. New Hampshire. Under the growth conditions used (L-broth, 37 degrees C, aerobic, batch culture), pAEX-5E remained segregationally stable in the pX01-/pX02+ and pX01-/pX02- derivatives for in excess of 100 culture generations, but was expelled from the pX01+/pX02+ and pX01+/pX02- derivatives (100% loss occurred after 101+/-3.8 and 54+/-6.0 culture generations, respectively). In the presence of antibiotic selection pressure to maintain pAEX-5E (5 microg erythromycin ml-1) no comparable loss of pX01 or pX02 was observed over 100 generations of growth in any of the derivatives of B. anthracis. Under these conditions the pX01+/pX02- derivative had an extended culture doubling time (td+/-S. E. of the mean) of 75.3 +/- 1.4 min compared with 47.3 +/- 1.1, 46.2 +/- 0.86 and 43.2 +/- 1.2 min for the pX01+/pX02+, pX01-/pX02+ and pX01-/pX02- derivatives, respectively. That antibiotic resistance was pAEX-5E-mediated was confirmed using a second antibiotic marker (kanamycin). After100 generations of growth in the presence of erythromycin, colonies were shown to have retained kanamycin resistance. Southern blot analysis, in conjunction with plasmid rescue to Escherichia coli confirmed that, after 100 culture generations in the presence of antibiotic selection pressure, pAEX-5E had remained structurally stable and had not integrated into the B. anthracis genome.

Animals↗
PubMed1999

Molecular markers linked to breeding system differences in segregating and natural populations of the cereal aphid Rhopalosiphum padi L.

The aphid Rhopalosiphum padi shows coexistence of sexual and asexual populations, providing an opportunity to study the evolution of breeding system variation in the context of theories on the origin and maintenance of sex. However, assessments of the distribution of sexual and asexual lineages of this aphid are complicated by the difficulties in rapidly characterizing their breeding system. To facilitate this task and to gain insight into the genetic relatedness between sexual and asexual genotypes, molecular markers linked to breeding system differences were recently developed. In this study, we have successfully converted a random amplified polymorphic DNA (RAPD) marker associated with life-cycle variation in R. padi into a codominant sequences-characterized amplified region (SCAR). Segregating and natural populations of known breeding systems were examined to evaluate the life cycle-SCAR marker association. Complete linkage was found in segregating populations while the association averaged 94% in field populations. Detailed analysis of allelic distribution and sequence divergence of the SCAR locus among sexual and asexual populations provides further evidence for a unique and apparently ancient loss of sexuality in this aphid. It also suggests that occasional gene flow occurs between populations differing in their breeding system, mediated by males produced by 'asexual' lineages. This system provides the possibility for the recurrent emergence of new asexual lineages, ensuring the longer persistence of asexuality, and would have important implications for the assessment of costs and benefits of sex in aphids.

Animals↗
PubMed2002

The P1 plasmid is segregated to daughter cells by a 'capture and ejection' mechanism coordinated with Escherichia coli cell division.

The fate of the P1 plasmid of Escherichia coli was followed by time-lapse photomicroscopy. A GFP-ParB fusion marked the plasmid during partition (segregation) to daughter cells at slow growth rate. The process differs from that previously inferred from statistical analysis of fixed cells. A focus of plasmid copies is captured at the cell centre. Immediately before cell division, the copies eject bidirectionally along the long axis of the cell. Cell division traps one or more plasmid copies in each daughter. They are not directed to a prescribed position but are free to move, associate and disassociate. Later, they are captured to the new cell centre to restart the cycle. A null P1 par mutant associates to form a focus, but it is neither captured nor ejected. A dominant negative ParB protein forms a plasmid focus that attaches to the cell centre but never ejects. It remains captive at the centre and blocks host cell division. The cells elongate. Eventually the intact focus is pushed to one side and the cells divide simultaneously in several places at the same time. This suggests that the wild-type plasmid imposes a regulatory node on the host cell cycle, preventing cell division until its own segregation is completed.

Bacterial Proteins↗
PubMed2003

Architecture of the ParF*ParG protein complex involved in prokaryotic DNA segregation.

The mechanism by which low copy number plasmids are segregated at cell division involves the concerted action of two plasmid-encoded proteins that assemble on a centromere-like site. This study explores the topology of the DNA segregation machinery specified by the parFG locus of TP228, a partition system which is phylogenetically distinct from more well-characterized archetypes. A variety of genetic, biochemical and biophysical strategies revealed that the ParG protein is dimeric. ParF, which is more closely related to the cell division regulator MinD than to the prototypical ParA partition protein of plasmid P1, is instead multimeric and its polymeric state appears to be modulated by ATP which correlates with the proposed ATP-binding activity of ParF. ParG interacts in a sequence-specific manner with the DNA region upstream of the parFG locus and this binding is modulated by ParF. Intriguingly, the ParF and ParG proteins form at least two types of discrete complex in the absence of this region suggesting that the assembly dynamics of these proteins onto DNA is intricate.

Adenosine Triphosphate↗
PubMed1997

Segregation analysis of ovarian cancer using diathesis to include other cancers.

Despite the recent cloning of BRCA1, BRCA2 and the mismatch repair genes, it will still be a long time before it is possible to specify any individual's risk for ovarian cancer based on her genotype. Most women concerned about their risk on the basis of one or two affected relatives do not belong to extensive ovarian cancer families. Risk calculations depend on a reliable genetic model for ovarian cancer derived, ideally, from the population from which an individual is drawn. We have carried out a segregation analysis using data collected from consecutive ovarian cancer patients in two different centres in the UK. Complex segregation analysis was carried out with the addition of diathesis as a separate parameter allowing other cancers, associated with ovarian cancer, to be taken into account. The use of diathesis in the derivation of this alternative model is described. Analysed under joint likelihood without diathesis, the gene frequency is 0.0028 and penetrance to age 70 years is 50%. This is in agreement with other published models. Incorporating diathesis into the model under joint likelihood gives similar parameters for a single locus model but gives the best fit with a two locus model where both genes are rare.

Adult↗
PubMed1999

Combined segregation and linkage analysis of nonsyndromic orofacial cleft in two candidate regions.

We applied a complex segregation analysis to 46 pedigrees with a total of 121 nuclear families and 660 individuals, to verify hypotheses regarding the inheritance of OFC and linkage with markers on chromosomes 6 and 2. The POINTER program for segregation analysis strongly rejected the hypothesis of no familial transmission of OFC in these families. When the hypothesis of a two-locus model was tested with COMDS, the analysis showed the presence of at least two loci and the model assuming a dominant major gene and a recessive modifier locus was statistically accepted. Given the fitted two-locus model, we tested for a possible linkage between the major OFC locus and the two markers studied. For D6S259, the estimate of the recombination fraction was theta = 0.098, corresponding to a LOD score around 2.1. On the contrary, the data analysis concerning the D2S378 marker showed an estimate of the recombination fraction not significantly different from the independence hypothesis.

Chromosomes, Human, Pair 2↗
PubMed2002

The shortened replicative life span of prohibitin mutants of yeast appears to be due to defective mitochondrial segregation in old mother cells.

Prohibitin proteins have been implicated in cell proliferation, aging, respiratory chain assembly and the maintenance of mitochondrial integrity. The prohibitins of Saccharomyces cerevisiae, Phb1 and Phb2, have strong sequence similarity with their human counterparts prohibitin and BAP37, making yeast a good model organism in which to study prohibitin function. Both yeast and mammalian prohibitins form high-molecular-weight complexes (Phb1/2 or prohibitin/BAP37, respectively) in the inner mitochondrial membrane. Expression of prohibitins declines with senescence, both in mammalian fibroblasts and in yeast. With a total loss of prohibitins, the replicative (budding) life span of yeast is reduced, whilst the chronological life span (the survival of stationary cells over time) is relatively unaffected. This effect of prohibitin loss on the replicative life span is still apparent in the absence of an assembled respiratory chain. It also does not reflect the production of extrachromosomal ribosomal DNA circles (ERCs), a genetic instability thought to be a major cause of replicative senescence in yeast. Examination of cells containing a mitochondrially targeted green fluorescent protein indicates this shortened life span is a reflection of defective mitochondrial segregation from the mother to the daughter in the old mother cells of phb mutant strains. Old mother phb mutant cells display highly aberrant mitochondrial morphology and, frequently, a delayed segregation of mitochondria to the daughter. They often arrest growth with their last bud strongly attached and with the mitochondria adjacent to the septum between the mother and the daughter cell.

Cell Division↗
PubMed2001

Pseudomonas aeruginosa in cystic fibrosis: cross-infection and the need for segregation.

Evidence-based reasons for segregation of patients colonized with Pseudomonas aerugionsa in the outpatient setting are unclear. To clarify local decisions, Pseudomonas genotyping of the local environment, patients and patient contacts was undertaken in 1993. The hospital environment was re-swabbed in 1997. Pseudomonas genotyping of old and new patients attending the North Staffordshire cystic fibrosis clinic has subsequently been undertaken and more recently been repeated on an annual basis to assess whether the same Pseudomonas genotypes can be found in both the environment and in patients, and whether the same Pseudomonas genotype can be transferred from one patient to another. No Pseudomonas genotype found in the local environment in 1993 or in 1997 has been found in any of our patients. Nine children attending the same special school for many years and sharing the same physiotherapy facilities showed no evidence of cross-infectivity. Except for siblings living in the same household our cross-infectivity rate is very low and where cross-infection has potentially occurred the level of contact between these patients has been minimal. This study does not support the suggestion that patients with cystic fibrosis attending the North Staffordshire clinic and colonized with Pseudomonas aeruginosa should be segregated from non-colonized patients.

Adolescent↗
PubMed2002

[Migration and health: is segregation inevitable?].

In the immigrant-absorbing countries migrants are regularly confronted with manifold forms of segregation and exclusion. This is also true of the health care system, thus impeding it in its humanitarian goals. One must try to understand why there should be a traditional tendency to encourage segregation. Among the reasons are explicit rejection of migration as such, poor understanding of other peoples, fear of infectious diseases and rising health care costs. In addition a misunderstanding of the integration process plays an important role. What is necessary is, firstly, a realistic view of the world-wide process of migration which inevitably affects the rich industrial nations and, secondly, respect for ethnic identity instead of an out-dated concept of assimilation.

Acculturation↗
PubMed2005

Results on quantitative trait loci for flushing date in oaks can be transferred to different segregating progenies.

Flushing date (bud burst) is one of the most important traits for the adaptation to different environments and climates in the temperate zone. Because of their wide geographic distribution, Quercus robur L. and Q. petraea (Matt.) Liebl. are suitable as model plants to study the genetic basis of bud burst. QTLs (Quantitative Trait Loci) with comparatively large effects have been mapped in a former study in a Q. robur x Q. robur full-sib family (French cross). In the present study, we performed a Bulked Segregant Analysis (BSA) in the F (1) progeny comprising 144 seedlings derived from a cross between a single Q. robur tree as common seed parent and five different pollen donors both from Q. robur and Q. petraea (Q. robur x Q. spp., Diekholzen crosses). In addition, markers linked to two bud burst QTLs with comparably strong effect in the above-mentioned full-sib family (French cross) were tested for their association with bud burst in the Q. robur x Q. spp. (Diekholzen) progeny. Using three microsatellite markers as anchor points, we could map QTLs on linkage group 7 and on linkage group 2, together explaining 16.2 % of the total phenotypic variance (PVE) in 1999 and 38.1 % in 2003. Out of 10 markers that segregated in both mapping progenies, four markers including the two microsatellite markers, showed a significant effect on bud burst in both materials. At microsatellite loci ssrQpZAG1/5 (linkage group 7) and ssrQpZAG119 (linkage group 2) alleles associated with early (allele 166 bp in ssrQpZAG1/5) and late bud burst (allele 57 bp in ssrQpZAG119) in the Q. robur x Q. robur full-sib family (French cross) showed a highly significant association with the same polarity of the effect in the Q. robur x Q. spp. (Diekholzen) progeny. The usefulness of these markers for marker-assisted selection in full-sib and half-sib families is discussed.

Genetic Linkage↗
PubMed1983

Clinical implications of chromosomal inversions. A pericentric inversion in No. 18 segregating in a family ascertained through an abnormal proband.

Chromosomal inversions are being detected in humans with increasing frequency due to the application of chromosomal banding techniques. Inversions have occurred in all chromosomal groups. These structural aberrations may lead to infertility, reproductive loss, or abnormal offspring. To illustrate their clinical significance, we report a family in which an inversion in chromosome No. 18 is segregating. This family was ascertained through a proband whose anomalies were consistent with the deletion 18q syndrome. The chromosomal imbalance originated by recombination within the parental inversion during meiosis. Consideration of this family and 6 others with similar breakpoints (18p11 and 18q12 or q21) suggests that the risk of unbalanced (recombinant) livebirths may be higher for female inv(18) heterozygotes than for males. The paucity of male carriers detected could be due to prenatal selection or chance. Overall, there may be preferential segregation for the aberrant chromosomes (inversions plus recombinants). Amniocentesis and cytogenetic analysis of pregnancy losses is recommended for families in which inversions are detected.

Abnormalities, Multiple↗
PubMed1999

Axial segregation of granular materials.

When mixtures of granular materials are rotated, it is often found that they segregate into bands, along the axis of rotation, which are rich in the various components. This effect is discussed experimentally and theoretically, with emphasis on a mechanism based on surface flow. The complimentary phenomenon of radial segregation is reviewed, and a mechanism is proposed. Finally, we consider the long-time behavior of rotating mixtures, particularly their anomolous coarsening. (c) 1999 American Institute of Physics.

Journal Article↗
PubMed2005

Segregation in aqueous methanol enhanced by cooling and compression.

Molecular segregation in methanol-water mixtures is studied across a wide concentration range as a function of temperature and pressure. Cluster distributions obtained from both neutron diffraction and molecular dynamics simulations point to significantly enhanced segregation as the mixtures are cooled or compressed. This evolution toward greater molecular heterogenity in the mixture accounts for the observed changes in the water-water radial distribution function and there are indications also of a change in the topology of the water clusters. The observed behavior is consistent with an approach to an upper critical solution point. Such a point would appear to be "hidden" below the freezing line, thereby precluding observation of the two-fluid region.

Journal Article↗
PubMed2006

Superficial segregation in nanoparticles: from facets to infinite surfaces.

We compare the superficial segregations of the Cu-Ag system for a nanoparticle and for surfaces that are structurally equivalent to each of its facet. Based on a lattice-gas model and within a mean-field formalism, we derive segregation isotherms at various temperatures in the canonical ensemble, i.e., for a given overall solute concentration, and in the semigrand canonical ensemble, i.e., for a given bulk solute concentration. If both processes are very similar for high temperatures, they differ substantially at lower temperatures. Due to the finite-size effect and the indirect coupling between facets and edges, the relative position of the phase transitions of the facets and the corresponding surfaces is inversed when displayed as a function of the solute bulk concentration. Moreover, we show that working in the semigrand canonical ensemble is a much more efficient way to study this phenomenon, although nanoparticles are "canonical" objects in essence.

Journal Article↗