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Biomedical subjects

D L Nelson

Publications and source records attributed to D L Nelson.

At least 163 records · Page 9Linked to original sources
PubMed1995

Positional cloning reaches maturity.

The identification of genes involved in human genetic disease is no longer the province of those who would make a career of 'not finding' a gene. Developments from the human genome initiative have vastly facilitated the process of localizing genetic intervals segregating mutations, as well as that of obtaining the physical regents necessary for characterizing the region. In a few years' time, efforts aimed at the assignment of genes to the physical map, coupled with increasing quantities of sequence data from both cDNA and genomic sources, will provide numerous candidate genes for analysis, with consequences for the approaches used to define the gene and mutations(s) involved in the disease of interest.

Animals↗
PubMed1995

The fragile X syndromes.

Fragile X syndrome is a leading cause of mental retardation worldwide, with an incidence of approximately one case in 2000 live births. It is amongst the most common of human genetic diseases, and was the first to be associated with an unstable trinucleotide (CGG) repeat sequence. It is also characterized by a chromosomal fragile site which was the first of (now) four such sites to be identified at the molecular level. Each shows very similar features suggesting that other representatives of this type of fragile site will likely involve similar sequences. As with the other unstable trinucleotide repeats, the sequence at the fragile X locus is found to be remarkably unstable upon genetic transmission, however many features differ from the other repeats. As repeat expansion at the fragile X locus results in loss of expression of the co-resident FMR1 gene, the basis for clinical features is best understood in this disorder. Two additional fragile sites in the vicinity have been identified, and at least one of these is associated with mental retardation.

Animals↗
PubMed1995

Metabolism by Schistosoma mansoni of a new schistosomicide: 2-[(1-methylpropyl)amino]-1-octanethiosulphuric acid.

In order to investigate the mode of action of a new class of schistosomicides, the N-alkylaminoalkanethiosulphuric acids, the [outer 25S] 2-[(1-methylpropyl)amino]-1-octanethiosulphuric acids was synthesized. Labelling studies of adult Schistosoma mansoni were performed in infected mice and in in vitro incubations. After a single oral dose of the drug to infected mice, 5 metabolites were detected by thin-layer chromatogrpahy in organic extracts of male and female adult schistosomes. In vitro studies showed that the same compounds were present in organic extracts obtained from adult male and female worms. One of these metabolites was identified by mass spectroscopy as being the dimeric disulphide derivative of the parent labelled thiosulphuric acid.

Animals↗
PubMed1995

Age effects in cued recall: sources from implicit and explicit memory.

In 2 experiments, young and old adults were compared on cued recall using direct and indirect test instructions. Participants studied words under an incidental orienting task of rating each word for concreteness. Test cues were meaningfully related to the targets, and participants used them either to recall the studied word (direct test) or to generate a related word (indirect test). Target words and test cues varied in the number of associates linked to them prior to the laboratory experience, and effects of the size of the sets of associates were used as indicators of implicit memory search. Age differences were observed in the effects of target and cue set size as well as in the effects of type of test instruction.

Adolescent↗
PubMed1995

Intragenic loss of function mutations demonstrate the primary role of FMR1 in fragile X syndrome.

Nearly all cases of fragile X syndrome result from expansion of a CGG trinucleotide repeat found in the 5' untranslated portion of the FMR1 gene. Methylation of the expanded repeats correlates with down-regulation of transcription of FMR1; thus fragile X syndrome is postulated to be due to a loss of function of the FMR1 gene product, and this has been demonstrated at the protein level. However, the nature of the mutation offers the possibility of methylation spreading to adjacent genes with consequent loss of expression and contribution to the phenotype. Deletions of FMR1 and flanking sequence (some of substantial size) have been reported in patients with phenotypes consistent with a diagnosis of fragile X-syndrome, however, none is strictly intragenic. We report here the identification of two different intragenic loss of function mutations in FMR1: a single de novo nucleotide deletion in a young male patient (IJ) and an inherited two basepair change in an Adult male (SD), each with classical features of fragile X syndrome.

Amino Acid Sequence↗
PubMed1995

Evolution of the cryptic FMR1 CGG repeat.

We have sequenced the 5' untranslated region of the orthologous FMR1 gene from 44 species of mammals. The CGG repeat is present in each species, suggesting conservation of the repeat over 150 million years of mammalian radiation. Most mammals possess small contiguous repeats (mean number of repeats = 8.0 +/- 0.8), but in primates, the repeats are larger (mean = 20.0 +/- 2.3) and more highly interrupted. Parsimony analysis predicts that enlargement of the FMR1 CGG repeat beyond 20 triplets has occurred in three different primate lineages. In man and gorilla, AGG interruptions occur with higher-order periodicity, suggesting that historical enlargement has involved incremental and vectorial addition of larger arrays demarcated by an interruption. Our data suggest that replication slippage and unequal crossing over have been operative during the evolution of this repeat.

Animals↗
PubMed1995

Production of monoclonal antibodies to Bruton's tyrosine kinase.

Bruton's X-linked agammaglobulinemia is caused by mutations in a cytoplasmic protein tyrosine kinase termed Bruton's tyrosine kinase (BTK). The protein is expressed in all members of the B cell lineage and is critical for B cell development. The protein consists of several modules, including a pleckstrin homology domain and the Src homology domains SH1, SH2, and SH3. We report here the production of monoclonal antibodies against the pleckstrin homology domain of human BTK. The antibody was produced by immunizing mice with a FLAG-BTK fusion protein. Hybridoma supernatants were screened by ELISA using a GST-BTK fusion protein as the antigen. Selected monoclonal antibodies recognize denatured BTK on Western blots of peripheral blood mononuclear cell lysates. Mouse BTK protein is also detected. These antibodies should be useful in assessing patients with immune deficiency, as well as in studying normal B cell development.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

An integrated physical and genetic map of a 35 Mb region on chromosome Xp22.3-Xp21.3.

We have constructed a detailed physical map of the 35 Mb region spanning human chromosome Xp22.3-Xp21.3. The backbone of the map is represented by a single oriented contiguous stretch of 585 overlapping yeast artificial chromosome (YAC) clones covering the entire region. The map is formatted with 615 map objects that include 324 YACs, 185 sequence tagged sites, 28 genes, 85 chromosomal breakpoints and 37 highly polymorphic markers. Physical mapping was both guided and confirmed using 183 bins defined by chromosomal breakpoints and by overlapping regions of YAC clones. The localization of polymorphic markers in the physical map permits the integration of physical and genetic data across the region. These data establish chromosome Xp22.3-Xp21.3 as one of the best characterized large regions in the human genome. The map should greatly facilitate finer scale mapping and sequencing as well as the identification of disease genes from this portion of the human genome.

Base Sequence↗
PubMed1995

Population survey of the human FMR1 CGG repeat substructure suggests biased polarity for the loss of AGG interruptions.

Both sequence length and sequence content are important parameters in determining stability of the fragile X syndrome CGG repeat. In order to estimate the incidence of uninterrupted CGG repeats in the general population and to gain insight into mechanisms responsible for the loss and acquisition of AGG interruptions, 406 randomly selected FMR1 CGG repeat alleles from four broad ethnic groups were assayed for AGG punctuation. Among the 79 different classes of alleles detected, long uninterrupted tracts of pure repeats were rare in the general population, with only 1/406 or 0.25% found at the instability threshold (34-37 pure CGG repeats). There was no significant difference (P>0.05) in the distribution of alleles with long (>20) pure repeat tracts among the different ethnic groups, suggesting that different ethnic groups should be equally susceptible to the development of the disease. Analysis of an additional 43 alleles with total repeat lengths between 35 and 50 repeats, revealed that highly interrupted CGG repeats alleles (>2 AGG interruptions) occur preferentially at modal repeat lengths in the population, providing confirmatory evidence that the presence of AGG interruptions confers stability. A consideration of length variation of the most 3' tract of pure repeats revealed a bimodal distribution pattern with maxima at approximately 10 and 20 repeats. Only unimodal distributions with maxima 9 or 10 were observed for the 5' tract and middle CGG tract within the FMR1 CGG repeat substructure. These results suggest that the loss of the most 3' AGG interruption or its conversion to CGG is a common event in the human population, occurring by a mechanism which preserves overall repeat length. This bias for loss of the distal-most AGG interruption likely plays an important part in predisposing human alleles to the development of the X syndrome.

Alleles↗
PubMed1995

A muscle-specific DNase I-like gene in human Xq28.

A novel cDNA which maps to human Xq28 has been isolated and characterized. Sequence similarity to DNase I is high at the DNA and peptide sequence levels. The transcript is present at highest levels in skeletal and cardiac muscle, with lower expression in other tissues. Mutation analysis has been performed using DNA samples from two unrelated patients with Barth syndrome, and from 11 unrelated patients with Emery-Dreifuss muscular dystrophy, two genetic disorders linked to Xq28. No disease-associated mutations were detected in the coding region of the gene; however, a novel 190 base pair insertion/deletion polymorphism was found in the 3' untranslated region. Translation of the long open reading frame found in the cDNA yields a putative 302 amino acid protein with 37.6% identity to human DNase I. The protein is predicted to contain a signal sequence at the amino terminus, a transmembrane domain near the carboxyl terminus, and a helix-loop-helix domain.

Amino Acid Sequence↗
PubMed1995

130 kb of DNA sequence reveals two new genes and a regional duplication distal to the human iduronate-2-sulfate sulfatase locus.

Deficiency of IDs activity results in Hunter Syndrome (mucopolysaccharidosis type II), a fatal X-linked recessive disorder. We report characterization of 28 cosmids around the IDS locus in Xq28. Four overlapping cosmids have been sequenced in their entirety generating a 130-kb contig. These studies show the fine structure of the IDS gene and identify an IDS pseudogene-like structure located 20 kb distal to the active gene. Two novel genes have also been identified in this sequence, and one of these genes is also locally duplicated. Both homologs are expressed, and a number of alternative transcript products have been characterized. The presence of a highly conserved pseudogene-like structure within a larger duplicated region close to the IDS gene has significant implications for the study of mutations at this locus.

Base Sequence↗
PubMed1995

Gonadal mosaicism for incontinentia pigmenti in a healthy male.

Incontinentia pigmenti (IP) is a genodermatosis that segregates as an X linked dominant trait with male lethality. The disease has been linked to Xq28 in a number of studies. A few affected males have been documented, most of whom have a 47,XXY karyotype. We report a family with two paternally related half sisters, each affected with IP. The father is healthy, clinically normal, and has a 46,XY normal male karyotype. Linkage analysis of 12 polymorphic markers (two X linked and 10 autosomal) confirms paternity. X inactivation studies with the human androgen receptor (HUMARA) indicate that the paternal X chromosome is inactivated preferentially in each girl, implying that this chromosome carries the IP mutation, and that the father is a gonadal mosaic for the IP mutation.

Abortion, Habitual↗
PubMed1995

Occupationally embedded exercise versus rote exercise: a choice between occupational forms by elderly nursing home residents.

OBJECTIVES: The provision of options in the occupational form that encourages meaningful choices and subsequent purposeful occupational performances is a basic premise of occupational therapy. This study examines the preferences of elderly nursing home residents when presented with an occupationally embedded exercise versus a rote exercise and addresses the methodological problems identified in similar past research. METHODS: Fifty-two elderly nursing home residents were presented with a choice between an occupationally embedded exercise that involved unilateral dunking of a small, spongy ball into a basketball hoop and a rote exercise that involved moving the arm above the head in a simulation of the dunking exercise. Both exercises required flexion of the shoulder joint. Random assignment of the 52 subjects into one of four groups controlled for the order of the presentation of the exercises and the order of the choice statements. RESULTS: Sixty-nine percent of the subjects chose the occupationally embedded exercise. Analysis with the significance of a proportion statistic revealed a statistically significant difference (z = 2.77; p (one-tailed) = .003). CONCLUSION: Results were consistent with the hypothesis that elderly nursing home residents would tend to choose the occupationally embedded exercise. To further confirm this basic premise of occupational therapy, future studies that investigate therapeutic patterns of movement embedded in common occupations are recommended.

Aged↗
PubMed1995

The fragile X premutation in carriers and its effect on mutation size in offspring.

The pattern of inheritance in the fragile X (fra(X)) mutation follows a multistage intergenerational process in which the premutation evolves into the full mutation and the characteristic phenotype of the fra(X) syndrome after passing through oogenesis or a postzygotic event. Findings from our multicenter study confirm a strong direct relationship between fra(X) premutation size in the mother and probability of a full mutation in offspring with the mutation. Remarkably, the best-fitting equations are nonlinear asymptotic functions. The close approximation to both the logistic model and Gompertz suggests a process of accumulation of errors in DNA synthesis, as has been proposed previously. We also note that a larger-than-expected number of daughters of transmitting males have premutations that are smaller than their fathers', and that proportion is significantly higher than the proportion of daughters whose premutations are smaller than their mothers'. Intergenerational decreases in premutation size have been reported in other trinucleotide-repeat disorders and also appear to be parent-of-origin specific. Thus, while intergenerational expansion to the full mutation in fra(X) may manifest a postzygotic event, decreases in mutation size may occur during or prior to meiosis.

Female↗
PubMed1994

Radioimmunotherapy of nude mice bearing a human interleukin 2 receptor alpha-expressing lymphoma utilizing the alpha-emitting radionuclide-conjugated monoclonal antibody 212Bi-anti-Tac.

The efficacy, specificity, and toxicity of bismuth (212Bi) alpha particle-mediated radioimmunotherapy was evaluated in nude mice bearing a murine lymphoma transfected with the human CD25 [human Tac; interleukin 2 receptor alpha (IL-2R alpha)] gene. The therapeutic agent used was the tumor-specific humanized monoclonal antibody anti-Tac conjugated to 212Bi. The human IL-2R alpha-expressing cell line was produced by transfecting the gene encoding human Tac into the murine plasmacytoma cell line SP2/0. The resulting cell line, SP2/Tac, expressed approximately 18,000 human IL-2R alpha molecules/cell. Following s.c. or i.p. injection of 2 x 10(6) SP2/Tac cells into nude mice, rapidly growing tumors developed in all animals after a mean of 10 and 13 days, respectively. The bifunctional chelate cyclohexyldiethylenetriaminepentaacetic acid was used to couple 212Bi to the humanized anti-Tac monoclonal antibody. This immunoconjugate was shown to be stable in vivo. Specifically, in pharmacokinetic studies in nude mice, the blood clearance patterns of i.v. administered 205/206Bi-anti-Tac and coinjected 125I-anti-Tac were comparable. The toxicity and therapeutic efficacy of 212Bi-anti-Tac were evaluated in nude mouse ascites or solid tumor models wherein SP2/Tac cells were administered either i.p. or s.c., respectively. The i.p. administration of 212Bi-anti-Tac, 3 days following i.p. tumor inoculation, led to a dose-dependent, significant prolongation of tumor-free survival. Doses of 150 or 200 microCi prevented tumor occurrence in 75% (95% confidence interval, 41-93%) of the animals. In the second model, i.v. treatment with 212Bi-anti-Tac 3 days following s.c. tumor inoculation also resulted in a prolongation of the period before tumor development. However, prevention of tumor occurrence decreased to 30% (95% confidence interval, 11-60%). In both the i.p. and s.c. tumor trials, 212Bi-anti-Tac was significantly more effective for i.p. (P2 = 0.0128 50/100 microCi 212Bi-anti-Tac versus 50/100 microCi Mik beta; P2 = 0.0142 150/200 microCi anti-Tac versus 150/200 microCi Mik beta) and for s.c. tumors (P2 = 0.0018 100 microCi anti-Tac versus 100 microCi Mik beta; P2 = 0.0042 200 microCi anti-Tac versus 200 microCi Mik beta 1) than the control antibody Mik beta 1 coupled to 212Bi at comparable dose levels. In contrast to the efficacy observed in the adjuvant setting, therapy of large, established s.c. SP-2/Tac-expressing tumors with i.v. administered 212Bi-anti-Tac (at doses up to 200 microCi/animal) failed to induce tumor regression.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗