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PubMed1993

Segregation analysis of random amplified polymorphic DNA (RAPD) markers in Picea abies Karst.

The reliability of arbitrarily primed amplification products was tested. The segregation analysis of 266 amplification products obtained using 17 different 10-mer oligonucleotides in 34 megagametophytes from a single tree of Picea abies was carried out. Fifty-four out of the 165 variable bands fit the 1:1 segregation ratio expected for Mendelian traits. The segregation ratio of a subset of six RAPD markers in five other individuals from the same population confirmed their genetic nature. Our results strengthen the evidence previously reported that RAPDs markers can be considered Mendelian traits useful in the detection of genetic variability among both different individuals and populations.

Base Sequence↗
PubMed1991

Chromosome strand segregation during sporulation in Bacillus subtilis.

After the initiation of spore formation in Bacillus subtilis, the products of the final round of DNA replication segregate into two cells, i.e. the prespore and the mother cell. The prespore, which is known to contain a single completed chromosome, develops into a mature endospore which can be readily separated from mother cells and non-sporulating cells on the basis of its resistance properties. We have used a procedure originally developed to label the terminus region of the B. subtilis chromosome to specifically label the newly synthesized strands of DNA during the final round of DNA replication before sporulation. We have purified prespore DNA and used strand-specific probes to measure the radioactivity incorporated. The results show that the sister chromosomes segregate at random into the prespore. This result has implications for the segregation of chromosomes during vegetative growth and for the generation of cellular asymmetry during sporulation.

Bacillus subtilis↗
PubMed1994

Lon-dependent proteolysis of CcdA is the key control for activation of CcdB in plasmid-free segregant bacteria.

The ccd locus contributes to the stability of plasmid F by post-segregational killing of plasmid-free bacteria. The ccdB gene product is a potent cell-killing protein and its activity is negatively regulated by the CcdA protein. In this paper, we show that the CcdA protein is unstable and that the degradation of CcdA is dependent on the Lon protease. Differences in the stability of the killer CcdB protein and its antidote CcdA are the key to post-segregational killing. Because the half-life of active CcdA protein is shorter than that of active CcdB protein, persistence of the CcdB protein leads to the death of plasmid-free bacterial segregants.

ATP-Dependent Proteases↗
PubMed1985

Balanced reciprocal translocations: risk factors for aneuploid segregant viability.

Reciprocal translocations were studied in two groups of balanced carrier couples: 202 had 210 translocation aneuploid between (LB) infants, and 95 couples had repetitive abortions (AB) without liveborn aneuploids. The observed translocation aneuploidies in the LB group were compared to predicted potential aneuploidies in AB by frequency of chromosome involvement, meiotic segregation mode, and mean trisomic, monosomic and combined genomic imbalances. Qualitative and quantitative differences identified genomic regions and chromosomes possibly vital for in utero survivability. LB aneuploidies indicate non-random chromosome involvement, selection of least detrimental segregants and segments, and predominant transmission from maternal balanced carriers (especially in 3:1 tertiary segregation, 93.5%). For an individual with a balanced reciprocal translocation and untested reproductive capability, an approach is given for predicting whether a translocation aneuploid conceptus will be liveborn or aborted.

Aneuploidy↗
PubMed1996

Unusual segregation of t(11;22) resulting from crossing-over followed by 3:1 disjunction at meiosis I.

Reciprocal translocation t(11;22)(q23;q11) is of particular interest because the unbalanced offspring of the translocation carriers usually present with a supernumerary derivative chromosome 22. This common unbalanced karyotype is the result of 3:1 chromosome segregation during meiosis. We report the third case of a rare segregation pattern of a paternal 11;22 translocation. The proband's karyotype revealed the presence of a der(11) and two copies of a der(22), i.e. 47,XX,t(11;22)(q23;q11),+der(22) t(11;22)pat. The karyotype is the result of paternal 3:1 segregation after crossing-over involving the derived and the normal chromosome 22, as revealed by chromosome polymorphism analysis. Contrary to the preferential maternal, transmission of this common unbalanced translocation, the data from the literature, including our case, may suggest preferential paternal transmission of this rare type of unbalanced translocation.

Abnormalities, Multiple↗
PubMed1983

Segregation of proteins and sodium in human plasma upon freezing.

The proteins and sodium in human source blood plasma are segregated and concentrated on freezing, particularly in plasma that is frozen slowly in a large container. The temperature and the concentration gradients at the freezing front induce a convection in the liquid phase and thus play the primary role in the segregation of proteins and sodium in the frozen mass. Unidirectional freezing, where the freezing front moves against gravity, minimizes segregation because the density gradient-induced convection is minimized at the solid-liquid interface. Microscopic observation of the freezing front of the plasma indicates that ice crystals are the primary solid formed. Their shape is generally irregular, and they become highly dendritic as the freezing rate increases. Apparently, the liquid phase at the freezing front is trapped between the ice crystals; it then undergoes a complex secondary freezing process at a lower temperature behind the primary freezing front of the ice crystals.

Blood Proteins↗
PubMed1982

The segregation into microsomal vesicles and core-glycosylation in vitro of a 300-kDa rat thyroglobulin subunit.

Translation of rat thyroid mRNA in a cell-free protein synthesis system derived from rabbit reticulocytes results in synthesis of a 300-kDa thyroglobulin polypeptide [C.G. Alvino et al. (1982) FEBS Lett. 137, 307-313]. In the presence of dog pancreas microsomal membranes this polypeptide is segregated into the microsomal vesicles and core-glycosylated, as shown by increased protection against proteolytic treatment and binding to concanavalin-A-Sepharose. The segregation process appears to be strictly coupled to glycosylation, i.e. no detectable amounts of unglycosylated chains are found in the vesicles, and both processes only occur cotranslationally. The glycosylated protein exhibits lower electrophoretic mobility with respect to its non-glycosylated form and comigrates with a glycosylated 330-kDa polypeptide found in rat thyroid epithelial cells cultured in vitro [F.S. Ambesi-Impiombato et al. (1980) Proc. Natl Acad. Sci. USA, 77, 3455-3459]. Both glycosylated and non-glycosylated forms are immunoprecipitated by antibodies to 19-S rat thyroglobulin. Some features of the tyroglobulin polypeptide segregation and glycosylation have been studied by synchronized translation of rat thyroid mRNA: (a) the signal sequence seems to be located at the amino-terminal portion of the nascent polypeptide chain; (b) the distribution of the carbohydrate units is mostly clustered in the amino-terminal half of the protein as monitored by posttranslational analysis of the polypeptides synthesized in the presence of pancreatic membranes during competition experiments carried out with the detergent Nonidet P40.

Animals↗
PubMed2006

Race, segregation, and physicians' participation in medicaid.

Many studies have explored the extent to which physicians' characteristics and Medicaid program factors influence physicians' decisions to accept Medicaid patients. In this article, we turn to patient race/ethnicity and residential segregation as potential influences. Using the 2000/2001 Community Tracking Study and other sources we show that physicians are significantly less likely to participate in Medicaid in areas where the poor are nonwhite and in areas that are racially segregated. Surprisingly-and contrary to the prevailing Medicaid participation theory--we find no link between poverty segregation and Medicaid participation when controlling for these racial factors. Accordingly, this study contributes to an accumulating body of circumstantial evidence that patient race influences physicians' choices, which in turn may contribute to racial disparities in access to health care.

Adult↗
PubMed1978

Reproductive compensation in families segregating for Cooley's anaemia in Ferrara.

The reproductive performance of 100 families segregating for Cooley's anaemia was studied and compared to the performance of 127 control families. The control families were those of the sibs of the parents in the segregating families. No differences was found in the variables which might affect fertility and fecundity in control and thalassaemic families, although a different shape of the distribution of the number of births per family was found; the distribution had a higher variance in thalassaemics than in controls. The interval between the birth of a normal and an affected child is significantly longer than the interval between the birth of an affected child and a subsequent one. It was thought that these findings are indicative of reproductive compensation in families segregating for Cooley's anaemia, and of the moderate effect of the genetic counselling given to them.

Adult↗
PubMed1979

The use of multiple thresholds and segregation analysis in analyzing the phenotypic heterogeneity of multifactorial traits.

(1) Three models based on multifactorial inheritance are introduced to account for phenotypic heterogeneities. These models are used to determine whether subforms of a triat are: (a) different degrees of the same process, (b) non-familial environmental variants of the same process, and (c) independently transmitted processes. (2) The parameters of each model consist of two population prevalences and either one, two, or three correlation coefficients which reflect the three hypotheses given above. The models are formulated so that a likelihood ratio test may be performed to discriminate between them. (3) The following types of analyses are described: (a) analysis of prevalence data with separate population prevalence estimates, (b) analysis of prevalence data with the proband a parent with specified spouse, (c) analysis of prevalence data with the proband an offspring with specified parents, and (d) the full segregation distribution of families using Complex Segregation Analysis. (4) When compared with the Analysis of Prevalences, Complex Segregation Analysis has the following advantages: (a) the number of degrees of freedom for parameter estimates is greater and separate estimates of the population prevalences are not necessary, (b) standard errors of the parameters are smaller, and (c) the power to discriminate models is increased. (5) Phenotypic heterogeneities such as age of onset, severity, and sex effect can be more completely understood by the methods of analyses described above. The nosology of familial disorders can also be clarified, and environments relevant to the transmission of the trait can be detected. This approach is particularly suitable for the analysis for behavioural traits since it does not require the assumption that environmental effects common to relatives be ignored. (6) Finally, our experience indicates that incorporating both prevalence and pedigree data into a single analysis decreases the time required to perform the analysis.

Environment↗
PubMed1994

Genetic epidemiology of hereditary non-polyposis colorectal cancer syndromes in Modena, Italy: results of a complex segregation analysis.

Complex segregation analysis was conducted in a series of patients with hereditary non-polyposis colorectal cancer (HNPCC) ascertained through probands registered in the Cancer Registry of the Health Care District of Modena in Northern Italy. Altogether there were 71 nuclear families segregating for HNPCC in 28 pedigrees. The analysis favoured the two-loci model, in which the segregation at the major locus is compatible with codominant transmission with a frequency of 0.0044 for the high-risk allele for HNPCC and a lifetime penetrance of 0.728 for heterozygotes.

Adult↗
PubMed2007

Complex segregation analysis accounting for GxE of bone mineral density in European pedigrees selected through a male proband with low BMD.

Osteoporosis is a common multifactorial disorder characterized by low bone mass (BMD) and high susceptibility to low-trauma fractures. Family and twin studies have found a strong genetic component in the determination of BMD, but the mode of inheritance of this trait is not yet fully understood. BMD is a complex trait whose expression is confounded by environmental influences and polygenic inheritance. Detection of potential gene-environment interactions is of great interest in the determination of bone health status. Here we have conducted segregation analyses, using the regressive class D models, in a sample of 100 European pedigrees (NEMO) with 713 subjects (524 measured for phenotypes) identified via a male with low BMD values at either the Lumbar Spine or the Femoral Neck. Segregation analyses were conducted on the residuals of LS-BMD and FN-BMD adjusted for gender, age and BMI. We tested for gene-covariate (GxE) interactions, and investigated the impact of significant GxE interactions on segregation results. Without GxE a major effect was found to be marginally significant in LS-BMD and highly significant in FN-BMD. For both traits the Mendelian hypothesis was rejected. Significant Age x gene and BMI x gene interactions were revealed. Accounting for GxE increased statistical evidence for a major factor in LS-BMD, and improved the fit of the data to the Mendelian transmission model for both traits. The best fitting models suggested a codominant major gene accounting for 45% (LS-BMD) and 44% (FN-BMD) of the adjusted BMDs. However, substantial residual correlations were also found, and these remained highly significant after accounting for the major gene.

Adult↗
PubMed1992

Non-linear processes in perceived region segregation: orientation selectivity of complex channels.

Models incorporating linear spatial-frequency- and orientation-selective channels explain many aspects of visual texture segregation. The inability of such models to fully explain texture segregation results, indicates that non-linear processes are also involved. One non-linearity that has been suggested is complex channels consisting of two stages of linear filtering separated by a rectification-type non-linearity (much like cortical complex cells). Here we further demonstrate the usefulness of complex channels in explaining texture segregation results and investigate the orientation-selectivity of the first stage of such complex channels. Our results suggest that the first stage is much more selective for orientation than are lateral geniculate nucleus cells, but that the first-stage orientation bandwidth is rather wide with some interaction occurring between perpendicular orientations.

Form Perception↗
PubMed2005

Segregation of urine calcium excretion in families ascertained for nephrolithiasis: evidence for a major gene.

BACKGROUND: The quantitative genetics of urine calcium excretion has not been established. It is a trait of interest because hypercalciuria is commonly found in subjects with nephrolithiasis. The aim of this study was to model the segregation of this trait in a sample of French-Canadian families ascertained through a stone former. METHODS: Major gene, polygenic, and mixed models were fit to 24-hour urine calcium excretion from 567 individuals in 221 nuclear families, while simultaneously taking into account gender, age at examination, body mass index (BMI), and the use of thiazide drugs. The nuclear families were extracted from 154 pedigrees, some of which were four generations, with at least two siblings with a history of calcium stones. RESULTS: All the proposed genetic models fit the data significantly better than the null model. The most parsimonious model was the mixed codominant/polygenic model but it was statistically indistinguishable from the single-gene codominant model. In both of these models the heritability attributable to the major gene was estimated to be 0.58. CONCLUSION: Our results suggest that a major gene with a relatively large effect on variation in urine calcium excretion is segregating in French-Canadian families with stone formers. This implies that the power of quantitative trait segregation analysis of urine calcium excretion may be increased in these families, and results indicate that it should be feasible to genetically map the quantitative trait locus.

Adult↗
PubMed2005

Integration and segregation in auditory scene analysis.

Assessment of the neural correlates of auditory scene analysis, using an index of sound change detection that does not require the listener to attend to the sounds [a component of event-related brain potentials called the mismatch negativity (MMN)], has previously demonstrated that segregation processes can occur without attention focused on the sounds and that within-stream contextual factors influence how sound elements are integrated and represented in auditory memory. The current study investigated the relationship between the segregation and integration processes when they were called upon to function together. The pattern of MMN results showed that the integration of sound elements within a sound stream occurred after the segregation of sounds into independent streams and, further, that the individual streams were subject to contextual effects. These results are consistent with a view of auditory processing that suggests that the auditory scene is rapidly organized into distinct streams and the integration of sequential elements to perceptual units takes place on the already formed streams. This would allow for the flexibility required to identify changing within-stream sound patterns, needed to appreciate music or comprehend speech.

Acoustic Stimulation↗
PubMed1998

Perceptual segregation and pitch shifts of mistuned components in harmonic complexes and in regular inharmonic complexes.

It is unclear whether the perceptual segregation of a mistuned harmonic from a periodic complex tone depends specifically on harmonic relations between the other components. A procedure used previously for harmonic complexes [W. M. Hartmann et al., J. Acoust. Soc. Am. 88, 1712-1724 (1990)] was adapted and extended to regular inharmonic complexes. On each trial, subjects heard a 12-component complex followed by a pure tone in a continuous loop. In experiment 1, a mistuning of +/- 4% was applied to one of the components 2-11. The complex was either harmonic, frequency shifted, or spectrally stretched. Subjects adjusted the pure tone to match the pitch of the mistuned component. Near matches were taken to indicate segregation, and were almost as frequent in the inharmonic conditions as in the harmonic case. Also, small but consistent mismatches, pitch shifts, were found in all conditions. These were similar in direction and size to earlier findings for harmonic complexes. Using a range of mistunings, experiment 2 showed that the segregation of components from regular inharmonic complexes could be sensitive to mistunings of 1.5% or less. These findings are consistent with the proposal that aspects of spectral regularity other than harmonic relations can also influence auditory grouping.

Acoustic Stimulation↗
PubMed1999

Sequential stream segregation in the absence of spectral cues.

This paper investigates the cues used by the auditory system in the perceptual organization of sequential sounds. In particular, the ability to organize sounds in the absence of spectral cues is studied. In the first experiment listeners were presented with a tone sequence ABA ABA ..., where the fundamental frequency (f0) of tone A was fixed at 100 Hz and the f0 difference between tones A and B varied across trials between 1 and 11 semitones. Three spectral conditions were tested: pure tones, harmonic complexes filtered with a bandpass region between 500 and 2000 Hz, and harmonic complexes filtered with a bandpass region chosen so that only harmonics above the tenth would be passed by the filter, thus severely limiting spectral information. Listeners generally reported that they could segregate tones A and B into two separate perceptual streams when the f0 interval exceeded about four semitones. This was true for all conditions. The second experiment showed that most listeners were better able to recognize a short atonal melody interleaved with random distracting tones when the distracting tones were in an f0 region 11 semitones higher than the melody than when the distracting tones were in the same f0 region. The results were similar for both pure tones and complex tones comprising only high, unresolved harmonics. The results from both experiments show that spectral separation is not a necessary condition for perceptual stream segregation. This suggests that models of stream segregation that are based solely on spectral properties may require some revision.

Adult↗
PubMed2004

Dynamic instability in a DNA-segregating prokaryotic actin homolog.

Dynamic instability-the switching of a two-state polymer between phases of steady elongation and rapid shortening-is essential to the cellular function of eukaryotic microtubules, especially during chromosome segregation. Since the discovery of dynamic instability 20 years ago, no other biological polymer has been found to exhibit this behavior. Using total internal reflection fluorescence microscopy and fluorescence resonance energy transfer, we observe that the prokaryotic actin homolog ParM, whose assembly is required for the segregation of large, low-copy number plasmids, displays both dynamic instability and symmetrical, bidirectional polymerization. The dynamic instability of ParM is regulated by adenosine triphosphate (ATP) hydrolysis, and filaments are stabilized by a cap of ATP-bound monomers. ParM is not related to tubulin, so its dynamic instability must have arisen by convergent evolution driven by a set of common constraints on polymer-based segregation of DNA.

Actins↗