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D Barker

Publications and source records attributed to D Barker.

At least 109 records · Page 6Linked to original sources
PubMed1987

Genetic linkage map of human chromosome 7 with 63 DNA markers.

High-density genetic maps of individual human chromosomes will permit accurate localization of disease-associated genes and provide signposts that will be useful in the construction of physical maps. We have constructed a genetic map of chromosome 7 with 63 polymorphic DNA markers by using segregation data from 23 three-generation families and recently developed multilocus linkage-analysis techniques. The map spans 250 centimorgans in females and 170 centimorgans in males, with much of the difference being concentrated in a few intervals. The density and informativeness of the markers are such that there is a high probability of detecting linkage to any disease gene on this chromosome for which 20 phase-known meioses are available.

Chromosome Mapping↗
PubMed1987

A genomic search for linkage of neurofibromatosis to RFLPs.

Our initial attempt to map NF was directed towards chromosomes 4 and 19, both of which had provided positive evidence for linkage in previous reports. This analysis showed no evidence in support of either hypothesis. Our second attempt at mapping NF was a general search of the genome, analysing a set of markers selected according to their degree of polymorphism, chromosomal location, ease of use, and availability. Data for linkage analysis were obtained from 17 multiplex families which are segregating a gene for NF. Linkage analyses were performed using PAP. Of note is the lod score of +1.17 at a recombination fraction of 0.1 between NF and the centromere of chromosome 17.

Chromosome Mapping↗
PubMed1986

Reinnervation and recovery of cat muscle receptors after long-term denervation.

After nerve injury muscles remain denervated until axons return to begin reinnervation and recovery. The delay between injury and recovery in human limb nerves averages 13 weeks after crush, and 16 weeks after transection and suture. In order to assess the effects of such long denervation periods on the recovery of cat muscle receptors, we crushed the common peroneal nerve and denervated peroneus brevis for 10 to 134 days; 39 days were allowed for reinnervation in each experiment. After 50 days denervation, the mean number of terminal bands in the regenerated spindle primary endings was 10.3 compared with a normal mean of 29.0. After 134 days, the mean was 0.6 and spindles were severely atrophied. Despite this most spindle afferent fibers continued to respond normally to ramp-and-hold stretch, abnormal responses being recognized as those that failed to maintain firing during the held phase of the ramp. After 50 days, 21% of spindle afferent fibers responded abnormally and about this proportion did so after all the longer denervation periods. Maximum afferent firing rates were all significantly lower than normal, and many afferent fibers fatigued more rapidly. Tendon organs were atrophied after 113 and 134 days and received fewer terminals, but their afferents fired apparently normally during muscle twitch. These results imply that the consequences of long-term denervation on human muscle spindles would be unlikely to affect the overall pattern of response to stretch of any Ia or II afferent fibers reinnervating them, though the quality of their response might be impaired.

Afferent Pathways↗
PubMed1986

Factors which equalize the representation of genome segments in recombinant libraries.

Genomic segments which contain inverted repetitions longer than 300 bp are frequently lost from recombinant libraries grown on rec+ hosts. We have found that 9% of phage lambda clones that contain 15-20-kb insertions of human or Drosophila DNA are inhibited on rec+ hosts and as a result will become under-represented in amplified genomic libraries. We have therefore examined several factors of both host and vector origin which affect the fidelity of representation of genomic sequences in recombinant DNA libraries constructed in bacteriophage lambda vectors. This loss may be diminished if the vector carries either a chi element or a functional gam gene. The most successful approach, however, involves using a host with mutations in recB, recC, and sbcB, or in recD. We have shown that recombinant clones which require such mutant hosts for growth are somewhat more likely to contain DNA derived from loci in the genome which are polymorphic than are clones recovered on conventional hosts.

Animals↗
PubMed1986

Pregnancy outcomes among adolescent and older women receiving comprehensive prenatal care.

This study compares three birth outcomes, gestational age, birthweight, and type of delivery, among adolescent and older mothers. Data were collected from 911 women who attended a comprehensive prenatal-care program in a large urban teaching hospital. Women aged 13-19 years were at increased risk for low-birth-weight babies (less than 2500 g) and for preterm infants of fewer than 38 weeks gestation, even with antenatal care, ethnicity, and other factors controlled. Results of bivariate analyses suggested that women aged 20-36 years are more likely than adolescent mothers to have a cesarean section; however, multivariate analyses suggested that maternal age was not an important factor in relation to type of delivery. Thus, even with similar comprehensive care, pregnant adolescents were at an increased risk of some adverse outcomes. However, the amount of antenatal care is a more important predictor of pregnancy outcome than is maternal age.

Adolescent↗
PubMed1986

Use of highly polymorphic DNA probes for genotypic analysis following bone marrow transplantation.

The use of DNA markers known as restriction fragment length polymorphisms is a sensitive and informative method of distinguishing patient and allogeneic donor cells after bone marrow transplantation. To apply the test, it is necessary in each case to find DNA probes that display patient-specific and donor-specific bands in Southern transfer hybridization. We have isolated a set of 12 cloned DNAs from highly polymorphic loci by which siblings can usually be distinguished. With just four of these probes, we can expect to distinguish the genotypes of the recipient and a sibling donor in more than 99% of cases (except between identical twins). The availability of many highly polymorphic probes also allows selection of an optimal probe for each case, one that can detect both the patient and donor-specific bands in a single hybridization with maximum resolution and sensitivity. We have applied these probes to the analysis of cells from peripheral blood and bone marrow after transplantation and demonstrated their usefulness in confirming engraftment of donor cells or graft rejection, and in detecting mixed lympho-hematopoietic chimerism.

Base Sequence↗
PubMed1985

Cystic fibrosis locus defined by a genetically linked polymorphic DNA marker.

A polymorphic DNA marker has been found genetically linked, in a set of 39 human families, to an autosomal recessive gene that causes cystic fibrosis (CF), a disease affecting one in 2000 Caucasian children. The DNA marker (called D0CRI-917) is also linked to the PON locus, which by independent evidence is linked to the CF locus. The best estimates of the genetic distances are 5 centimorgans between the DNA marker and PON and 15 centimorgans between the DNA marker and the CF locus, meaning that the location of the disease gene has been narrowed to about 1 percent of the human genome (about 30 million base pairs). Although the data are consistent with the interpretation that a single locus causes cystic fibrosis, the possibility of genetic heterogeneity remains. The discovery of a linked DNA polymorphism is the first step in molecular analysis of the CF gene and its causative role in the disease.

Aryldialkylphosphatase↗
PubMed1985

Form and classification of motor endings in mammalian muscle spindles.

The presynaptic features of 234 motor endings supplied to cat hindlimb muscle spindles have been studied in teased, silver preparations, and the postsynaptic features of a further 27 endings have been studied in serial, 1 micron thick, transverse sections. In the presynaptic study motor endings received by the three types of intrafusal muscle fibre were compared with the endings supplied to spindles by the various functional categories of motor axon. Three forms of motor ending were found that had significantly different presynaptic features. These forms correspond closely to those previously identified in the literature as p1 (beta), p2 (dynamic gamma) and trail (static gamma). The results of the postsynaptic study showed that the degree of indentation of the intrafusal muscle fibres by motor axon terminals increases with greater distance from the primary ending, irrespective of muscle-fibre type. We conclude that the postsynaptic form of intrafusal motor endings is determined by distance from primary ending and muscle-fibre type. It is not determined by type of motor axon, and cannot be correlated with presynaptic form so as to produce a unified classification of intrafusal motor endings.

Animals↗
PubMed1985

High-affinity and low-affinity vanadate binding to sarcoplasmic reticulum Ca2+-ATPase labeled with fluorescein isothiocyanate.

Conditions were found that allowed both the fluorescence detection of vanadate binding to the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum and the vanadate-induced formation of two-dimensional arrays of the enzyme. The fluorescence intensity of fluorescein isothiocyanate-labeled Ca2+-ATPase increased with high-affinity vanadate binding (Ka = 10(6) M-1) as reported by Pick and Karlish (Pick, U. and Karlish, S.D. (1982) J. Biol. Chem. 257, 6120-6126). The Ca2+ and Mg2+ dependencies for high-affinity vanadate binding were similar but not identical to those for orthophosphate. In addition, it was found that there is low-affinity (Ka = 380 M-1) vanadate binding, which causes a 25% decrease in fluorescence. The Ca2+ and Mg2+ dependencies of the low-affinity vanadate binding were different from those of orthophosphate or high-affinity vanadate binding. The covalent attachment of fluorescein isothiocyanate (FITC) in the ATP site of the Ca2+-ATPase did not affect the formation of two-dimensional arrays, as detected by negatively stained electron micrographs. Vanadate concentrations high enough to saturate the low-affinity binding caused two-dimensional arrays as reported by Dux and Martonosi (Dux, L. and Martonosi, A. (1983) J. Biol. Chem. 258, 2599-2603). In addition, freeze-fracture replicas of quick-frozen specimens showed rows of indentations in the inner leaflet of the bilayer that corresponds to the arrays seen on the outer leaflet. This appearance of indentations suggests that low-affinity vanadate binding causes a transmembrane movement of the Ca2+-ATPase. By contrast, high-affinity vanadate binding was shown to cause neither array formation nor the appearance of indentations.

Animals↗
PubMed1985

Sensory reinnervation of cat peroneus brevis muscle spindles after nerve crush.

Results are presented of examining the postcrush sensory reinnervation of cat peroneus brevis muscle spindles previously investigated physiologically by Hyde and Scott. It is shown that primary and secondary endings were successfully restored in their final form in the early stages of recovery. The primary endings were shorter than normal and had fewer transverse bands; 12% were judged to be hyperinnervated. Some secondary endings showed signs of growth through the primary region apparently designed to establish secondary terminals in the opposite pole. This is compared with the collateral regeneration of intact motor axons in partially denervated muscle. It is concluded that the defects observed in the regenerated sensory endings had no effect on their functional recovery.

Animals↗
PubMed1985

Sensory reinnervation of muscles following nerve section and suture in cats.

The common peroneal nerve was transected and repaired by epineurial suture in nine cats. In a further nine the nerve was transected twice and similarly repaired so as to produce a short autograft. Recovery of stretch receptors in peroneus brevis was monitored histologically and physiologically from six to fifty weeks. In recovery after single neurotomy functionally identifiable muscle-spindle and tendon-organ afferents were reduced to 25% and 45% of normal, respectively; after double neurotomy (autograft) both were reduced to about 10% of normal. Muscle spindles were reinnervated with annulospiral terminals, or wholly abnormal fine axon terminals, or both. Recovery evidently entails not only a reduction in number of stretch afferents, but also the making of some incorrect reconnections that presumably result in abnormal proprioceptive feedback and reflex action. When a graft is used the sensory impairment is compounded.

Animals↗
PubMed1985

The tendency to IUGR in preterm infants born to young women enrolled in a comprehensive prenatal program.

Low-birthweight infants born to young women in an urban poor and multiethnic community who attended an intensive comprehensive prenatal program were studied. Of the 801 young women followed, 69 (8.6%) delivered infants weighing less than or equal to 2500 gm. Despite comprehensive care, there was a high prevalence of maternal anemia though other obstetric factors were not significantly increased. Of the 69 low-birthweight infants, 82.6% were below the 50th percentile for weight. There was a tendency toward intrauterine growth retardation (IUGR) among preterm infants which was pronounced after 33 weeks gestation. Further studies are needed to determine what developmental insult could arrest growth and lead in some instances to preterm birth and in others to IUGR.

Adolescent↗
PubMed1985

Sleep apnea in amyloidosis.

Obstructive sleep apnea (OSA) occurs in patients with narrowing of the pharyngeal airway due to a variety of pathologic conditions. We documented obstructive and mixed sleep apnea in a patient with narrowing of the airway caused by macroglossia associated with amyloidosis. Tracheostomy relieved the symptoms of OSA (hypersomnolence, confusion upon awakening, and hyperkinesis during sleep) despite the emergence of striking central sleep apnea following the procedure.

Aged↗
PubMed1984

A second type II restriction endonuclease from Thermus aquaticus with an unusual sequence specificity.

A type II restriction endonuclease activity free of TaqI was prepared from Thermus Aquaticus YT. The fraction contains two endonucleolytic components with apparently different specificities, however the major activity is sufficiently dominant to allow partial digestion analysis of the position of recognition sites. A precise determination of the location of cleavage sites in pBR322 DNA and a computer-aided search for regions of homology in the vicinity of the cut sites indicate that this enzyme recognizes the nonpalindromic sequences GACCGA or CACCCA. Other related sequences are not cleaved, in particular, GACCCA and CACCGA, indicating that the enzyme requires the identity of nucleotides in the first and fifth positions, a type of specificity that has not been previously reported. The position of cleavage is located outside of the site and is represented as: (Formula: see text).

Base Sequence↗
PubMed1984

Restriction sites containing CpG show a higher frequency of polymorphism in human DNA.

Unique loci in the human genome were examined with restriction enzymes in order to detect restriction fragment length polymorphisms (RFLPs). Of 31 arbitrary loci, nine were detectably polymorphic, reflecting ten polymorphic restriction sites. Nine of the ten polymorphic sites were revealed with two restriction enzymes, Msp I and Taq I, whose recognition sequences have in common the dimer sequence CpG. The cytosines in the CpG sequence are known to be frequently methylated in mammals, and the occurrence of significant variation in Msp I and Taq I sites supports the view that methylated cytosine residues are hotspots for mutation in mammalian DNA.

5-Methylcytosine↗
PubMed1984

DNA polymorphic loci mapped to human chromosomes 3, 5, 9, 11, 17, 18, and 22.

Using the techniques of Southern filter hybridization and somatic cell genetics, seven genomic DNA fragments recognizing DNA polymorphic loci were mapped to specific chromosomes and regions of chromosomes. The seven probes, isolated from human genomic libraries, lacked repetitive sequences and were hybridized to DNA isolated from a set of human-rodent somatic cell hybrids segregating human chromosomes. These probes detected DNA sequences on human chromosomes 3, 5, 9, 11, 17, 18, and 22. These DNA polymorphic sites, which occur in 10% or greater of the population, will serve as markers for linkage studies with known polymorphic loci as well as to establish linkage with disease loci.

Animals↗
PubMed1984

A locus on chromosome 11p with multiple restriction site polymorphisms.

We have discovered and characterized a new polymorphic locus on chromosome 11p, D11S12, defined by an arbitrary genomic DNA segment cloned in the plasmid pADJ762. Four different polymorphic restriction sites with minor allele frequencies greater than 5% are revealed by Southern hybridization of this probe and its derivatives to digests of human DNAs. These include two MspI sites, a TaqI site, and a BclI site. The frequencies of the common haplotypes at this locus have been determined in a Utah population. Significant linkage disequilibrium has been demonstrated to exist between some pairs of polymorphic sites. A molecular map of this region has been determined, and the polymorphic sites have been localized. Comparison of physical separation with degree of linkage disequilibrium reveals an interesting case where an MspI site and a TaqI site that are separated by 6.8 kilobases (kb) show a greater degree of disequilibrium with each other than they do with two polymorphic sites located between them. One of the two interior sites is a BclI site that is approximately 0.2 kb away from the TaqI site but shows the same degree of disequilibrium with the TaqI site as with the MspI site 6.7 kb away. Although there is significant linkage disequilibrium at this locus, there are four major haplotypes with frequencies of 5% or greater, and the polymorphic information content (PIC) of this locus is .64.

Alleles↗