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Biomedical subjects

B N White

Publications and source records attributed to B N White.

At least 37 records · Page 2Linked to original sources
PubMed1994

Genetic variation of the St. Lawrence beluga whale population assessed by DNA fingerprinting.

Recent surveys suggest that the endangered St. Lawrence beluga (Delphinapterus leucas) population is not recovering significantly despite 20 years of protection. Dead individuals that have been autopsied show high levels of tumours and infections. This situation could be a result of pollution, loss of genetic variation, inbreeding depression or a combination of these factors. Analyses of DNA fingerprints from St. Lawrence belugas with three minisatellite probes (Jeffreys 33.6, 33.15 and M13) indicate a reduced level of genetic variation compared to Beaufort Sea animals. The average band-sharing between individuals of the St. Lawrence beluga population for the three probes (0.534, 0.573 and 0.478, respectively) was significantly higher than that of the Beaufort Sea beluga population (0.343, 0.424, 0.314, respectively). Higher levels of mean allele frequency in the St. Lawrence belugas (0.33 vs. 0.21) suggest that this population is composed of individuals which are related. Inbreeding depression could therefore be a factor in the lack of recovery of the St. Lawrence beluga population.

Alleles↗
PubMed1994

Forensic application of repetitive DNA markers to the species identification of animal tissues.

Highly repetitive DNA markers have been used for determining the species origin of animal tissues in cases of illegal commercialization and poaching of game animals. This approach has been used in cases involving white-tailed deer (Odocoileus virginianus), moose (Alces alces) and black bear (Ursus americanus). Digesting the DNA with various restriction enzymes, agarose electrophoresis and staining with ethidium bromide revealed unique banding patterns for each species. These patterns have been used to distinguish meat from game animal species from commercial sources of meat and organs. Data are presented from two Ontario court cases that demonstrate the application of the procedure.

Animals↗
PubMed1993

Isolation, sequencing and characterization of two cDNA clones coding for trypsin-like enzymes from the midgut of Aedes aegypti.

In order to understand the regulation of trypsin genes by the blood meal, we constructed a cDNA library from mRNA isolated from midguts of blood-fed female Aedes aegypti. The library was screened with a Drosophila melanogaster trypsin-like gene; twelve cDNAs were isolated and sequenced. Two clones were 846 bp and 788 bp long with 762 bp and 716 bp open reading frames, respectively. The cDNAs were identified as coding for serine proteases by the presence of conserved serine, histidine and aspartic acid residues; the presence of an aspartate residue at position 176 suggests that the clones were derived from trypsin-like gene transcripts rather than chymotrypsin or other serine proteases. One of the clones contained a 5' untranslated region and coding regions for putative signal and activation peptides, suggesting that the product is secreted as an inactive zymogen and processed by autoactivation. Southern analysis of genomic DNA suggests that trypsin is encoded by a multigene family in A. aegypti.

Aedes↗
PubMed1993

Application of DNA fingerprinting to enforcement of hunting regulations in Ontario.

DNA fingerprinting has been used in investigations of 40 cases of infractions of hunting regulations involving white-tailed deer (Odocoileus virginianus) and moose (Alces alces) in Ontario. In most of these cases, individual-specific DNA fingerprints obtained with the Jeffrey's 33.15 multilocus probe were used to link the animal remains found at the illegal kill site to blood and tissue samples of the dead animal associated with a suspect. DNA fingerprints from 27 white-tailed deer and 19 moose were obtained in order to establish the level of band-sharing in DNA fingerprints among unrelated individuals in each species. We also determined the levels of band-sharing among animals from the same region and calculated the probability of two individuals sharing the same DNA fingerprint. Details are presented from cases in which the evidence was presented and accepted by Ontario courts.

Animals↗
PubMed1992

Application of DNA fingerprinting to the recovery program of the endangered Puerto Rican parrot.

The Puerto Rican parrot was reduced to approximately 13 animals in 1975 and as a conservation measure, a captive population was established from a few founders taken from the wild between 1973 and 1983. The number of successful breeding pairs in captivity has been low, and the captive breeding program has not been as productive as that of the closely related Hispaniolan parrot. Therefore, a genetic study was initiated to examine the relative levels of relatedness of the captive founders using levels of bandsharing in DNA fingerprints. Unrelated captive founder Puerto Rican parrots had the same average level of bandsharing (0.41) as second-degree relatives of the Hispaniolan parrot (0.38, P > 0.05), with an inbreeding coefficient of 0.04. High levels of bandsharing (> 40%) between pairs of males and females correlated with reproductive failure, suggesting that inbreeding depression is partly responsible for the low number of breeding pairs. Consequently, DNA profiling can be used to guide the captive breeding program for the Puerto Rican parrot, and other endangered species, by identifying pairs of males and females with low levels of bandsharing.

Animals↗
PubMed1992

Characterization and assessment of an avian repetitive DNA sequence as an icterid phylogenetic marker.

The first tandemly repeated sequence examined in a passerine bird, a 431-bp PstI fragment named pMAT1, has been cloned from the genome of the brown-headed cowbird (Molothrus ater). The sequence represents about 5-10% of the genome (about 4 x 10(5) copies) and yields prominent ethidium bromide stained bands when genomic DNA cut with a variety of restriction enzymes is electrophoresed in agarose gels. A particularly striking ladder of fragments is apparent when the DNA is cut with HinfI, indicative of a tandem arrangement of the monomer. The cloned PstI monomer has been sequenced, revealing no internal repeated structure. There are sequences that hybridize with pMAT1 found in related nine-primaried oscines but not in more distantly related oscines, suboscines, or nonpasserine species. Little sequence similarity to tandemly repeated PstI cut sequences from the merlin (Falco columbarius), saurus crane (Grus antigone), or Puerto Rican parrot (Amazona vittata) or to HinfI digested sequence from the Toulouse goose (Anser anser) was detected. The isolated sequence was used as a probe to examine DNA samples of eight members of the tribe Icterini. This examination revealed phylogenetically informative characters. The repeat contains cutting sites from a number of restriction enzymes, which, if sufficiently polymorphic, would provide new phylogenetic characters. Sequences like these, conserved within a species, but variable between closely related species, may be very useful for phylogenetic studies of closely related taxa.

Animals↗
PubMed1990

Genetic mapping of two new DNA markers in Xq26-q28 relative to the fragile-X syndrome locus.

We have characterized and genetically mapped two new DNA markers (DXS311 and DXS312) with respect to 10 existing loci in Xq26----Xq28 in a set of 15 families in which the fragile-X [fra(X)] syndrome was segregating. Two-point and multipoint linkage analyses were performed taking into account the incomplete penetrance of the fra(X) mutation. The most likely order on the basis of these data is centromere-DXS79-DXS10-DXS311-DXS86-(F9-DXS99 )-(DXS98-DXS312)-fra(X)-DXS52- DXS15-F8C-telomere. DXS98 and one of the new loci, DXS312, were found to be the proximal markers closest to the fra(X) locus. The order F9-(DXS98-DXS312)-fra(X) was found to be 5.9 x 10(4) times more likely than the order (DXS98-DXS312)-F9-fra(X).

Chromosome Mapping↗
PubMed1990

Genetic mapping of X-linked albinism-deafness syndrome (ADFN) to Xq26.3-q27.I.

X-linked albinism-deafness syndrome (ADFN) was described in one Israeli Jewish family and is characterized by congenital nerve deafness and piebaldness. The ADFN mutation probably affects the migration of neural crest-derived precursors of the melanocytes. As a first step toward identifying the ADFN gene, a linkage study was performed to localize the disease locus on the X chromosome. The family was found to be informative for 11 of 107 RFLPs along the X, and two-point analysis showed four of them--factor 9 (F9), DXS91, DXS37, and DNF1--to have definite or suggestive linkage with ADFN. Multipoint linkage analysis indicated two possible orders within this cluster of loci, neither of which was preferable. In both orders F9 was the most distal, and the best estimate for the location of ADFN was between F9 and the next proximal marker (8.6 cM from F9 [Z = 8.1] or 8.3 cM from F9 [Z = 7.9]). These results suggest that the ADFN is at Xq26.3-q27.1. Disagreement between our data and previous localization of DXS91 at Xq11-q13 was resolved by hybridization of the probe pXG-17, which detects the DXS91 locus, to a panel of somatic cell hybrids containing different portions of the X chromosome. This experiment showed that this locus is definitely at Xq24-q26. Together with the linkage data, our results place DXS91 at Xq26 and underscore the importance of using more than one mapping method for the localization of molecular probes.

Albinism↗
PubMed1989

Relative tumorigenicities of hybrid cells with and without HSR-bearing chromosomes from a human melanoma cell line.

Some cell types within the human melanoma cell line MeWo contain homogeneously staining regions (HSRs) consisting of repetitive DNA sequences and ribosomal RNA (rRNA) genes derived from chromosome 15. To further examine the association between enhanced tumorigenicity and the presence of HSR-bearing chromosomes, hybrid cell lines were constructed by fusing X-HSR-containing MeWo cells with ouabain-resistant, HPRT-deficient Chinese hamster ovary cells and culturing in HAT medium containing ouabain. A hybrid containing the X-HSR chromosome and several MeWo chromosomes was more tumorigenic in BALB/c nude mice than derivative cells lacking the X-HSR and human chromosome 18. However, since this enhanced tumorigenicity could be due to sequences on either the X-HSR or chromosome 18, a second series of hybrids was constructed by micro-cell fusion. In this case, the tumorigenicity of hybrid cells containing 2 copies of the X-HSR as the only MeWo chromosome was similar to that of derivative cells lacking these chromosomes. Cytogenetic analysis revealed that the nucleolar organizer regions (NORs) on the HSR were inactive in the hybrid cells. Our data indicate that DNA sequences amplified on MeWo HSRs do not enhance tumorigenicity under experimental conditions in which rRNA genes are not expressed. As the only active NORs in MeWo HSR-containing cells are on the HSRs, we suggest that expression of these amplified rRNA genes is responsible for the selective growth advantage of these cell types in nude mice. Our data also indicate that the enhanced tumorigenicity of MeWo HSR-containing cells is not due to co-amplification of a dominant oncogene.

Animals↗
PubMed1989

Double in situ hybridization in combination with digital image analysis: a new approach to study interphase chromosome topography.

Double in situ hybridization with mercurated and biotinylated chromosome specific DNA probes in combination with digital image analysis provides a new approach to compare the distribution of homologous and nonhomologous chromosome targets within individual interphase nuclei. Here we have used two DNA probes representing tandemly repeated sequences specific for the constitutive heterochromatin of the human chromosomes 1 and 15, respectively, and studied the relative arrangements of these chromosome targets in interphase nuclei of human lymphocytes, amniotic fluid cells, and fibroblasts, cultivated in vitro. We have developed a 2D-image analysis approach which allows the rapid evaluation of large numbers of interphase nuclei. Models to test for a random versus nonrandom distribution of chromosome segments are discussed taking into account the three-dimensional origin of the evaluated 2D-distribution. In all three human diploid cell types the measurements of target-target and target-center distances in the 2D-nuclear image revealed that the labeled segments of the two chromosomes 15 were distributed both significantly closer to each other and closer to the center of the nuclear image than the labeled chromosome 1 segments. This result can be explained by the association of nucleolus organizer regions on the short arm of chromosome 15 with nucleoli located more centrally in these nuclei and does not provide evidence for a homologous association per se. In contrast, evaluation of the interphase positioning of the two chromosome 1 segments fits the random expectation in amniotic fluid and fibroblast cells, while in experiments using lymphocytes a slight excess of larger distances between these homologous targets was occasionally observed. 2D-distances between the labeled chromosome 1 and 15 segments showed a large variability in their relative positioning. In conclusion our data do not support the idea of a strict and permanent association of these homologous and nonhomologous targets in the cell types studied so far.

Cell Nucleolus↗
PubMed1989

DNA marker studies show that Machado Joseph disease is not an allele of the Huntington disease locus.

Machado Joseph Disease (MJD) is a progressive spinocerebellar atrophy (SCA) with an autosomal dominant mode of inheritance. On the basis of some similarities in the clinical features and in the abnormal profiles of brain proteins, it has been suggested that MJD might be an allele of the Huntington Disease (HD) locus. Using the DNA probe (pK082), we analyzed the linkage between the DNA marker locus D4S10 and the MJD locus in two large kindreds. The data exclude linkage between these two loci at a distance of 10 cm (Z = - 2.02). Since the D4S10 locus is linked to the HD locus at a distance of approximately 4 cm, we conclude that MJD is not an allele of the HD locus.

Alleles↗
PubMed1988

Parental origin of the extra chromosome in the cat eye syndrome: evidence from heteromorphism and in situ hybridization analysis.

Two individuals, a boy and girl, with a clinical diagnosis of cat eye syndrome had an extra bisatellited chromosome. In the girl, the diagnosis was made on the basis of coloboma of the right iris, right preauricular pit, and imperforate anus; in the boy, bilateral colobomata of the iris, down-slanting palpebral fissures, right preauricular skin tag, and right preauricular pit. Multiple staining techniques were used to characterize the extra chromosomes. With G-banding the extra chromosome usually appeared monocentric with two major G-positive bands, but with satellites on both ends; with C-banding, two C-band positive regions were evident, indicating that the chromosomes were likely dicentric. Silver staining demonstrated the presence of NORs near each end; Q-banding showed satellites on each end, differing in brightness and size. The chromosomes of the parents were normal; comparisons of Q-band heteromorphisms of the acrocentric chromosomes of the parents with those of the extra chromosome showed in each case one short arm/satellite region of the extra chromosome identical in appearance to one chromosome 22 of the mother and the other end of the extra bisatellited chromosome identical to the short arm/satellite of the mother's second chromosome 22. This extra chromosome, then, is the result of a maternal meiotic error in each case. In situ hybridization studies using the chromosome 22-derived probe p22/34, which identifies locus D22S9, showed 16% of the cells from the female patient to have silver grains on the proximal long arm of the normal chromosome 22 and 14% on the extra chromosome, while 10% of cells from the male had grains on the normal chromosomes 22 and an equal number on the extra chromosome, confirming the chromosome 22 origin of the extra chromosome in these patients.

Abnormalities, Multiple↗
PubMed1988

A complete deletion of the factor IX gene and new TaqI variant in a hemophilia B kindred.

We report a hemophilia B kindred in which the proband has a complete deletion of the factor IX gene extending a minimum of 80 kilobase pairs (kb) 3' of the gene. This individual has severe factor IX deficiency with no detectable circulating factor IX protein. In common with one previous report, despite a total deletion of the factor IX gene, this patient has not developed antibodies to factor IX. The mother of the proband was found to have a new TaqI variant of the factor IX gene on the nondeletion-bearing X chromosome. The location of the altered TaqI site was found to be 5' of exon IV between residues 9731-9734 and does not affect the function of the factor IX protein. The familial natures of both the variant allele and the deletion were established. In addition a study of this kindred at the DXS99 locus demonstrated the first reported recombination event between this site and the factor IX gene.

Blood Coagulation Tests↗
PubMed1988

Tumorigenicity of ten karyotypically distinct cell types present in the human melanoma cell line MeWo-A.

The earliest passage of the human melanoma cell line, MeWo-A, consists of ten cell types that can be distinguished on the basis of chromosome markers. Two of these cell types have chromosomes with long homogeneously staining regions (HSR) containing sequences derived from the short arm of a chromosome #15. In one cell type the HSR is found on a chromosome #15 and in the other it is on a der(15;10)-HSR chromosome. Four other cell types were identifiable by morphologic differences of the short arm of chromosome #13, whereas, the four remaining cell types were identifiable by the presence of prominent satellites on other chromosomes. This study was directed at assessing the relative tumorigenic properties of the different cell types by injecting different numbers of cells intraperitoneally, subcutaneously, or intravenously into Balb/c nude mice. The primary tumors and nodules that developed in the peritoneal cavity and lungs were explanted into tissue culture. One hundred metaphase chromosome spreads from each established cell line were analyzed cytogenetically to detect changes in proportions of the different cell types. The cell type containing the der(15;10)-HSR chromosome was present in only 20% of the cells injected, but increased in proportion to between 28% and 98% after growth in nude mice. Although the degree of selection of the der(15;10)-HSR-containing cell type was influenced by the number of cells injected, the consistent selection of these cells strongly suggests that this cell type has a growth advantage. Because the 15-HSR-containing cell type rarely increased in proportion, it is likely that the HSR by itself can not confer the enhanced tumorigenic phenotype but requires the expression of other sequences present on other MeWo chromosomes to provide the selective growth advantage to the cells in which it is found.

Animals↗
PubMed1988

Carrier detection strategy in haemophilia A: the benefits of combined DNA marker analysis and coagulation testing in sporadic haemophilic families.

A province wide study of carrier detection methods in haemophilia A is reported. The principal objective of this project was to compare the relative merits of coagulation testing and DNA marker analysis in carrier diagnosis for a large unselected haemophilic population. Factor VIII:C (F.VIII:C) and von Willebrand factor antigen (vWf:Ag) were measured on plasma samples sent to a central laboratory. Coagulation results were analysed by a logistic regression model of discrimination. Of 91 potential carriers tested, 15% had indeterminate coagulation test carrier probabilities. Two restriction fragment length polymorphisms were analysed in 123 women (42 obligate carriers and 81 potential carriers). The BcII polymorphism within the F.VIII gene and the locus DXS 52, approximately 5 cM (centimorgan) from F.VIII were used as DNA markers. Of the 81 potential carriers tested with RFLP analysis, a carrier diagnosis was achieved in 52%. Studies with the F.VIII intragenic BgII polymorphism in 23 of these families gave no additional information. Thirty-nine potential carriers remained undiagnosed after DNA marker analysis. Twenty-seven of these women were from families with a sporadic case of haemophilia. In this group of 27 women, 14 were found to have high probability carrier estimates derived from their coagulation tests. Combined coagulation and RFLP data was available in 42 potential carriers. Disagreement between DNA and coagulation carrier diagnoses was found in four instances. In each case, the coagulation data resulted in a carrier probability of indeterminate value. This study emphasizes some of the limitations associated with DNA marker linkage analysis as it pertains to haemophilia A carrier detection. Where a previous family history exists and appropriate females are informative for the DNA markers, this type of analysis is very productive. However, large numbers of potential carriers from 'sporadic' haemophilia families were a factor in this project. With this in mind, an optimal service for haemophilia A carrier diagnosis must continue to offer reliable coagulation test probabilities in addition to DNA marker studies.

Blood Coagulation Tests↗