Biomedical subjects
M A Walter
Publications and source records attributed to M A Walter.
Consumer product aspiration and ingestion in children: analysis of emergency room reports to the National Electronic Injury Surveillance System.
Inadvertent aspiration or ingestion of products in children is a reportable problem. The National Electronic Injury Surveillance System (NEISS) monitors 119 hospitals for product (nonfood) hazards through a network of emergency room physicians. Coins (52%) remain the most frequently ingested object (1988-1989). Pins, including nails and bolts, are second in rank. Spheres (eg, balls) are the most common cause of death. Most deaths (97%) occur in the home. Younger children (13.4 versus 22.7 months) are more at risk for death. This analysis suggests that shape, as well as availability, is important in children's injuries and deaths. Accurate reporting to NEISS of all aspirated objects remains essential so that product safety and the public's health can be improved. Food product injuries, however, are not reported to NEISS.
Epstein-Barr virus detection in neck metastases by polymerase chain reaction.
Cervical nodal metastasis from occult carcinomas represents a diagnostic challenge. This is a common presentation of undifferentiated nasopharyngeal carcinoma (UNPC), but metastatic carcinomas from other sites must be considered. UNPC has the distinguishing feature of a close association with Epstein-Barr virus (EBV). Since the polymerase chain reaction (PCR) can detect EBV in archival tissues, it offers significant advantages over previous methods for the detection of viral genomes. Its extreme sensitivity allows analysis of small samples from needle aspirates. Using the polymerase chain reaction to amplify EBV sequences from archival tissues, 15 of 18 NPC samples were positive for EBV. Of these 18, 14 of 14 with UNPC were positive, 1 of 2 with squamous cell carcinoma (SCC) were positive, and 10 of 2 with adenocarcinoma were positive. All 6 UNPC metastatic to lymph nodes were positive. Carcinoma metastatic to cervical nodes from 17 of 17 non-UNPC occult primaries lacked EBV. This demonstrates the utility of EBV detection by the polymerase chain reaction in the evaluation of patients with metastases to neck nodes from occult primary carcinomas in order to identify cases of UNPC.
Ig H chain variable and C region genes in common variable immunodeficiency. Characterization of two new deletion haplotypes.
Common variable immunodeficiency, a disorder characterized by diminished antibody production, manifests clinically as an increased susceptibility to bacterial infections. We have investigated the Ig H chain V and C region gene segments in 33 patients with common variable immunodeficiency, to identify the possible role these genes may have in the molecular basis of the defect. No major deletions were recognized for the VH gene segments of the VH2, VH5, and VH6 families, nor were there any differences in the RFLP patterns of mu- or alpha- switch regions or of C gamma genes. Two new deletion haplotypes were identified for the C region genes, the first encompassing C gamma 1 on a different haplotype from the C gamma 1 deletion described previously, and the second a novel deletion encompassing both C gamma 2 and C gamma 4. Based on these and previously described deletions in the IGHC region, we postulate that homologous regions are involved in the deletion process and that other new deletions likely exist in the population.
A deletion map of the human immunoglobulin heavy chain variable region.
Analysis of VH gene segments deleted in the process of immunoglobulin heavy chain (IGH) variable region assembly in three series of monoclonal B cell lines has been used to determine the human VH region organization. A deletion map of the relative positions of 21 different VH gene segments has been determined. The characterization of B cell lines from three unrelated adults of two racial groups yielded the same relative VH gene segment order, suggesting that the overall order of VH genes in the normal population is constant. This VH gene segment order was consistent with what we had previously generated from physical mapping techniques. DH segments from the second DH cluster, distinct from the major DH locus 3' of the VH region, were not observed to be used in 32 different rearrangements. Approximately 77% of the VH-(D)JH rearrangements involved VH gene segments within 500 kb of the JH region, indicating that human B cell lines preferentially rearrange JH-proximal VH gene segments. The switch, observed in mice, from the fetal use of JH-proximal VH gene segments to an adult VH use dependent upon VH family size may therefore not occur in humans. This detailed map of the VH gene segments is a necessary prerequisite for understanding VH usage in development and disease.
Localization and genetic linkage of the human immunoglobulin heavy chain genes and the creatine kinase brain (CKB) gene: identification of a hot spot for recombination.
The immunoglobulin heavy chain (IGH) gene cluster and the gene coding for the brain form of the enzyme creatine kinase (CKB) have previously been localized to chromosome 14, at 14q32.3 and 14q32, respectively. Here we report more precise regional localization of these genes by dosage studies using DNA from a child hemizygous for the region from 14q32.32 to 14qter. CKB and IGH are present in a single dose in the proband. Dosage studies in a second patient with a similar but smaller deletion due to a ring chromosome 14 show that CKB is proximal to the IGH cluster. An EcoRI restriction site polymorphism was found with probes for the CKB gene. Linkage analysis of family data indicates that CKB is closely linked to IGH. Linkage analysis also revealed unusually high recombination (beta = 3.2%) between the C delta and C gamma 3 genes of the IGH constant region, which are only 60 kb apart. This finding, in combination with a previous observation of linkage equilibrium in the region, suggests that the C delta-C gamma 3 region contains a recombination hot spot.
Susceptibility to multiple sclerosis is associated with the proximal immunoglobulin heavy chain variable region.
15 immunoglobulin heavy chain constant (CH) and variable region (VH) polymorphisms were selected to span the entire length of the heavy chain cluster. These polymorphisms were examined in 34 sib pairs concordant for multiple sclerosis (MS) and in 23 sporadic MS patients. Allele frequencies were calculated for the 2 MS patient groups and compared with those found in a control population from the same geographical location and of similar ethnic background. No significant association was found between MS and the 7 CH region polymorphisms examined. However, a significant correlation between the MS phenotype and a VH2 family polymorphism was observed in both MS patient populations (familial MS patients chi 2 = 8.16, P less than 0.005; sporadic MS patients chi 2 = 8.90, P less than 0.005). One allele of the VH2-5 gene segment was found to be over-represented in both MS groups. VH2-5 has recently been physically mapped close to the CH region, between 180 and 360 kb away. These results indicate that a locus near or within the CH-proximal VH region is associated with increased susceptibility to MS.
Predicting radioresistance in early glottic squamous cell carcinoma by DNA content.
Nuclear DNA content has been implicated as a prognostic factor in an increasing number of tumor types. Current data on the role of DNA content in head and neck carcinoma are conflicting and incomplete. To evaluate the role of DNA content in predicting radioresistance, 29 patients with T1N0M0 squamous cell carcinoma of the glottic larynx who had undergone uniform curative radiotherapy and whose clinical outcome was known had flow cytometric analysis for DNA content performed on their tumors with paraffin-embedded archival tissues. Five aneuploid lesions and 24 diploid lesions were identified. All aneuploid lesions occurred in radioresistant tumors. The probability of an aneuploid tumor failing radiotherapy was highly significant at p = .016. No DNA discordance was found in a sampling of half of the radioresistant lesions' pretreatment and recurrent specimens, for a 100% predictive value of moderate statistical power. On the basis of these findings, patients with aneuploid T1 glottic lesions should be referred for primary surgical therapy.
Nonuniform linkage disequilibrium within a 1,500-kb region of the human immunoglobulin heavy-chain complex.
We have characterized 10 VH polymorphic loci of the VH2, VH3, VH4, and VH5 families. Eight of 10 VH polymorphisms were found to be insertion/deletion polymorphisms, probably the result of nonhomologous recombination over the course of evolution of the current human VH repertoire. The 10 VH polymorphic loci were analyzed in 10 three-generation and 10 two-generation Canadian caucasoid families. Linkage disequilibrium (allelic association) was measured between pairs of VH polymorphic loci, and 12 significant associations were found. The degree of linkage disequilibrium measured between IGH polymorphic loci was then compared with the physical distance separating the loci. The physical distance between IGH polymorphic loci does not entirely determine the degree of linkage disequilibrium between polymorphic loci. Two regions, one in the VH region (between VH3f-2 and VH5-2 and one in the CH region (between C delta and C gamma 3), were found to have linkage disequilibrium values approximately 1/3,000 of that observed in other portions of the IGH region. The previous identification of recombinants in the C delta-to C gamma 3 region indicates that these areas of low linkage disequilibrium are consistent with the presence of recombination hot spots. The observed high amount of recombination in the subtelomeric portion of chromosome 14 therefore appears to be the result of specific hot spots for recombination, rather than a general increase in recombination in this region.
The physical organization of the human immunoglobulin heavy chain gene complex.
Two dimensional DNA electrophoresis (2D-DE) was used to map the variable (VH) region of the human heavy chain immunoglobulin gene cluster. Seventy-six VH gene segments were mapped to specific SfiI, BssHI and NotI fragments by 2D-DE. We have determined that a common insertion/deletion polymorphism of 80 kb, involving three VH gene segments, occurs in the VH region. The physical map suggests that the evolution of the human IGH gene complex involved duplication of blocks containing different VH families. This physical map will allow comparison of the usage of VH loci in human ontogeny with their proximity to the CH region. Knowledge of the germline repertoire of a particular DNA source studied in essential as the number of the dispersed VH gene segments of VH families, especially of the VH5 family, is variable. 2D-DE, as illustrated here for the IGH gene cluster, has general application in the development of large scale physical maps of gene and repeat families.
A multigene deletion in the immunoglobulin heavy chain region in a highly atopic individual.
Highly atopic individuals, with marked allergy, have extremely elevated total plasma IgE levels. To determine if atopy could be associated with structural alterations involving the IGHE gene of the immunoglobulin heavy chain constant region, the genomic DNA from five atopic individuals was examined. We describe here the identification of a deletion of approximately 120kb, including the IGHA1, IGHGP, IGHG2, AGHG4, and IGHE genes of the IGH constant region, in one atopic patient. This deletion arose de novo from a maternally derived chromosome. The deletion, although apparently not the primary cause of the atopic phenotype of this patient, could be indirectly responsible for the phenotype by exposing aberrant immunoglobulin-regulating elements within the paternally derived IGH constant region.
Genetic polymorphisms of the VH3 gene family.
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A method for two-dimensional DNA electrophoresis (2D-DE): application to the immunoglobulin heavy chain variable region.
The scarcity of single-copy probes creates difficulty in the generation of large-scale physical maps of mammalian gene families. A simple method of two-dimensional DNA electrophoresis (2D-DE) has been developed to overcome this problem. DNA (2 micrograms) is digested with a rare-cutting restriction endonuclease and size separated by pulsed-field gel electrophoresis (PFGE). The DNA, still contained within the lane of the PFGE gel, is digested with a second frequent-cutting restriction enzyme and is subjected to an electrical field perpendicular to that of the PFGE. 2D-DE allows the simultaneous mapping, to large restriction fragments, of all the genes detected by a particular probe. The human immunoglobulin variable region was used as an example for this procedure. Two VH5 genes, on 8- and 9-kb EcoRI fragments, were mapped to 200- and 65-kb SfiI fragments, respectively, by 2D-DE. This technique will be particularly useful in the generation of physical maps of complex human gene families and of repeat families.
Complete physical map of the human immunoglobulin heavy chain constant region gene complex.
We have found by pulsed-field gel electrophoresis that the human immunoglobulin heavy chain constant region gene complex maps entirely to a 350-kilobase (kb) Mlu I fragment. The enzyme Eag I was used with pulsed-field gel electrophoresis alone and in double digests with Spe I to map the region. C gamma 3, of the C gamma 3-C gamma 1-C psi epsilon 1-C alpha 1 cluster, maps 60 kb to the 3' side of C delta; C gamma 2 of the C gamma 2-C gamma 4-C epsilon-C alpha 2 cluster maps 80 kb to the 3' side of C alpha 1, where C gamma 3 encodes the constant region of the immunoglobulin gamma 3 chain, C gamma 1 encodes the constant region of the immunoglobulin gamma 1 chain, etc. C psi gamma maps 35 kb to the 3' side of C alpha 1 and is in the same transcriptional orientation as the other genes. Although in the cloned DNA many CpG-containing restriction sites were identified, most of these were methylated in peripheral blood leukocytes. The sites that were not methylated were predominantly found in three clusters, or Hpa I tiny fragment islands. One was found on the 5' side of C mu; the other two lie 30 kb to the 3' side of each of the C alpha genes and could indicate the presence of regulatory sequences or genes. A region showing strong linkage disequilibrium between all C gamma genes spans at least 160 kb. The 70-kb C mu-C gamma 3 region, however, shows no linkage disequilibrium, possibly indicating a recombination hot spot. The immunoglobulin heavy chain constant region has been almost entirely cloned and mapped, and thus most rearrangements occurring in this region should be detectable.
RsaI polymorphism of a human immunoglobulin VH5 subclass locus.
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Physical linkage of a human immunoglobulin heavy chain variable region gene segment to diversity and joining region elements.
Antibody genes are assembled from a series of germ-line gene segments that are juxtaposed during the maturation of B lymphocytes. Although diversification of the adult antibody repertoire results in large part from the combinatorial joining of these gene segments, a restricted set of antibody heavy chain variable (VH), diversity (DH), and joining (JH) region gene segments appears preferentially in the human fetal repertoire. We report here that one of these early-expressed VH elements (termed VH6) is the most 3' VH gene segment, positioned 77 kilobases on the 5' side of the JH locus and immediately adjacent to a set of previously described DH sequences. In addition to providing a physical map linking human VH, DH, and JH elements, these results support the view that the programmed development of the antibody VH repertoire is determined in part by the chromosomal position of these gene segments.
Analysis of genetic variation reveals human immunoglobulin VH-region gene organization.
We have investigated the extent of genetic variation and the number of germ-line heavy-chain-variable (VH) genes to obtain information on the organization and repertoire of the VH genes. Our studies revealed extensive genetic variation in this region, indicated by restriction-endonuclease site polymorphisms. Analysis of the distribution of selected polymorphic loci revealed evidence of linkage disequilibrium, particularly between VH2 and VH3 subclass loci, indicating that the subclasses are interdispersed in the human germ-line chromosome. Absolute correlation was detected between alleles of a VH2 locus and the alleles of three VH3 loci, evidence for an extra set of VH genes, which are present in 48% of the Caucasian population. A preliminary estimate of the number of VH genes, approximately 50, indicates a smaller number of VH genes than suggested by the amount of protein variation. The extensive genetic variation we have observed may be associated with genetic differences in the immune response and potentially with variable susceptibility to autoimmune disorders.
Apa I polymorphism of a human immunoglobin VH3 subclass locus.
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