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E R Schmidt

Publications and source records attributed to E R Schmidt.

At least 37 records · Page 2Linked to original sources

Trocar site seeding of inapparent gallbladder carcinoma during laparoscopic cholecystectomy.

There are increasing reports of seeding of tumor at the trocar sites following laparoscopic cholecystectomy in patients with unexpected or inapparent gallbladder carcinoma. A patient is reported here whose primary tumor appeared controlled by surgery and radiation, but who died of the disease after developing implant metastases at three untreated trocar sites. The second case report illustrates the difficulty in identifying gallbladder cancer during laparoscopic cholecystectomy, and the importance of a diligent preoperative effort to establish the diagnosis. Current literature suggests that tumor implantation occurring during laparoscopic cholecystectomy for inapparent carcinoma adversely affects prognosis, and, until the effect of laparoscopy on the spread of this tumor is better understood and controlled, open operation should be performed when carcinoma of the gallbladder is suspected. When laparoscopic cholecystectomy is done for inapparent gallbladder cancer, surgical and adjuvant radiotherapy to the trocar sites appears to improve outcome in association with extended treatment to the gallbladder bed and adjacent areas. Recent reports suggest that progress in diagnostic, surgical, and adjuvant techniques could substantially improve survival in carcinoma of the gallbladder.

Adenocarcinoma↗

A community based approach to bicycle helmet use counts.

OBJECTIVE: Bicycle helmet use has become an important measure of the effectiveness of bicycle safety programs and the effectiveness of helmet legislation. Accounts of analytical comparisons of observation site selection methods are scarce. This report addresses this gap by reporting the relative effectiveness and costs of two alternative approaches to the selection of observation sites for helmet use counts. METHODS: The community based (COBA) method of site selection entailed asking community informants to identify locations frequented by young bicycle riders. In the bicycle club/map (CLMA) method, site selections were based on recommendations from club members of sites at which cyclists were likely to be found and through examination of maps, keying on local features. These alternative site selection methods were compared in terms of their overall and cost effectiveness in locating youth riders. RESULTS: Despite fewer observer hours and fewer sites in a sparsely populated rural county, the COBA method yielded greater numbers of riding youth and from 1.9 to 4.6 times more youth riders per observer hour than did the CLMA method in two densely populated suburban counties. In addition, costs per youth rider observed associated with the COBA method were 2.9 to 7.0 times lower than those associated with the CLMA method. CONCLUSIONS: Community based site identification is both more efficient in locating youth riders and more cost effective.

Bicycling↗

Sequence and evolution of the gene for the monomeric globin I and its linkage to genes coding for dimeric globins in the insect Chironomus thummi.

We isolated genomic clones containing sequences encoding globins I and IA from a Chironomus thummi thummi genomic library. Three clones contain globin IA (ctt-1A) genes, while one contains a globin I (ctt-1) gene. The coding regions of the four genes are identical except for the single base substitution accounting for the globin I/IA polymorphism. The noncoding DNA flanking the coding region is more than 98% similar, confirming a previous hypothesis that the globin ctt-1 and ctt-1A genes are alleles. Hemoglobins I and IA are monomeric in the insect hemolymph. Earlier in situ hybridization studies suggested that monomeric and dimeric globin genes are clustered at different chromosomal loci. In situ hybridization of ctt-1 DNA to polytene salivary gland chromosomes places the ctt-1 gene on the same band as genes for the dimeric globins II beta and VIIB, forcing revision of the earlier hypothesis that genes for monomeric and dimeric globin genes are at different loci. The evolution of the ctt-1 and ctt-1A alleles and of the two globin gene loci are discussed.

Amino Acid Sequence↗

Transposition of minisatellite-like DNA in Chironomus midges.

Cla elements are a family of tandem repetitive DNA sequences present in the genome of several Chironomus species. Interspersed clusters of Cla elements are widely distributed all over the chromosomes in C. thummi thummi, while they seem to be limited to the centromeric regions in the closely related subspecies C. t. piger. Here we present molecular evidence that this differential distribution is due to a transposition of Cla elements during evolution of the C. t. thummi genome. We have cloned a "filled" integration site (containing a Cla element cluster) from C. t. thummi and the corresponding "empty"genomic site from C. t. piger and other related species. The comparison shows that tandem repetitive elements may be mobilized together with flanking DNA.

Animals↗

Centromeric heterochromatin and satellite DNA in the Chironomus plumosus species group.

Species of the Chironomus plumosus group display significant differences in their amount of centromeric heterochromatin. A tandem-repetitive satellite-like DNA has been isolated from C. plumosus. This DNA accounts for a major part of the centromeric heterochromatin. The DNA element has a Sau3AI restriction site ("Sau elements") and a monomer length of 165 or 166 bp. It is A-T rich (73%) and reveals a moderate DNA curvature, as shown by gel migration and computer analysis. The chromosomal localization and genomic organization of Sau elements were studied in 24 Chironomus species by in situ hybridization and (or) Southern analysis. The DNA is predominantly located in the centromeric regions of nine species, six from the plumosus group and three others. In some cases, inter- and intra-specific differences in the size of the centromeric heterochromatin seem to correlate with the strength of Sau element hybridization signals. Few species contain Sau repeats outside of the centromeres (C. borokensis, C. plumosus). Additionally, Sau elements are revealed to be present in ectopic threads between centromeres, and in B chromosomes found in C. borokensis and C. annularius.

Animals↗

Divergent evolution of an "orphon" histone gene cluster in Chironomus.

The histone genes of the midge Chironomus thummi thummi are organized in tandemly repeated gene groups, each containing the four core histone genes plus an H1 gene. These repetitive gene groups are found at five different loci, linked on one chromosomal arm. In addition to the clustered gene groups an isolated histone gene group exists which is found spatially separated on a different chromosome ("orphon" gene group). These orphon genes have been cloned and analysed in detail. Nucleotide sequence and in situ hybridization data suggest that the orphon gene group was established early during chironomid speciation, possibly by a transposition-like mechanism. This allowed the genes to be moved as an integer group. The comparison of orphon and "clustered" histone genes in C. thummi thummi indicates that the early spatial separation of the orphon genes from their tandemly organized relatives may have stimulated divergent sequence evolution. This is particularly true for the orphon H1 gene, which has diverged considerably by unusual mutation mechanisms. The translocation of normally clustered genes to new genomic sites may favour the generation of sequence variants, which could fulfill specialized functional tasks.

Animals↗

Structural and functional differences between histone H1 sequence variants with differential intranuclear distribution.

The chromatin of most cell types contains several different sequence variants of histone H1. The functional role of this heterogeneity is not known. In the larval tissues of the midge, Chironomus thummi, there are H1 variants of two types. H1 II-1, H1 II-2, and H1 III-1 have similar amino acid sequences and appear uniformly distributed in polytene interphase chromosomes. The total number of gene copies per genome for this type of H1 histones is about 40 in C. th. thummi and 50-60 in C. th. piger. In contrast, histone H1 I-1 is encoded by a single copy gene in C. th. thummi and by two to four genes in C. th. piger. It has a divergent structure and is found only in a limited number of condensed chromosome sites. The N-terminal domain of H1 I-1 contains an insertion that is lacking in the other H1 variants and that is part of a variant-specific bipartite sequence Lys-Ala-Pro-Lys-Ala-Pro-Xaa10-Lys-Val-Ala in front of the conserved central domain. N-terminal peptides of H1 I-1 including this motif, in contrast to the homologous peptide from H1 II-1, competed with the drug Hoechst 33258 for binding to the minor groove of the DNA double helix. Repeats of the sequence Lys-Ala-Pro are also present at the same distance from the conserved central domain, in a single H1 variant of a nematode and of a green alga. The motif could interact with linker DNA in intranuclear targeting or packaging a condensed subtype of chromatin, or both.

Amino Acid Sequence↗

The sex determining region of Chironomus thummi is associated with highly repetitive DNA and transposable elements.

The dominant male sex determiner in chromosome III of the midge Chironomus thummi thummi is closely linked to a large cluster of tandem-repetitive DNA elements, the Cla elements, which are otherwise highly repetitive and distributed over more than 200 sites on all chromosomes. Chromosome III displays a hemizygous cluster of Cla elements in males but not in females. The chromosomal location of this hemizygous Cla element cluster is in the region of the male determiner M as localized by cytogenetic analysis. With Cla elements as hybridization probe, it was possible to clone a large part of the sex determining region. Molecular analysis of the DNA of males and females in this region displayed a number of differences between the two sexes. One striking difference is an unusual transposable element associated with the male sex determining region. The sex determining region also contains several other tandem-repetitive DNA elements in addition to the Cla elements. They are interspersed with single copy DNA. The accumulation of repetitive elements in the sex determining region interpreted as the result of a lack of recombination between the male/female heteromorphic region, although recombination in the other sections of chromosome III occurs.

Animals↗

Bicycle helmet use among Maryland children: effect of legislation and education.

Although bicycle helmets are effective in preventing head injuries, use of helmets among children remains infrequent. In response to the bicycling deaths of two children, Howard County, Maryland, became the first US jurisdiction to mandate use of bicycle helmets for children. Schoolchildren were lectured by police about the law before its enactment. Prelaw and postlaw helmet use was observed in Howard County and two control counties: Montgomery (which sponsored a community education program) and Baltimore County (no helmet activities). Prelaw crude helmet use rates for children were 4% (95% confidence interval [CI] 0% to 10%) for Howard, 8% (95% CI 3% to 13%) for Montgomery, and 19% (95% CI 5% to 33%) for Baltimore. Postlaw rates were 47% (95% CI 32% to 62%), 19% (95% CI 11% to 27%), and 4% (95% CI 0 to 11%), respectively. The rate of bicycle helmet use by Howard County children is now the highest documented for US children. A similar increase in helmet use among children younger than 16 years nationwide could prevent about 100 deaths and 56,000 emergency-department-treated head injuries annually. Physicians and other health professionals should consider proposing and supporting the Howard County approach in their communities.

Adolescent↗

The organization, localization and nucleotide sequence of the histone genes of the midge Chironomus thummi.

Several histone gene repeating units containing the genes for histones H1, H2A, H2B, H3 and H4 were isolated by screening a genomic DNA library from the midge Chironomus thummi ssp. thummi. The nucleotide sequence of one complete histone gene repeating unit was determined. This repeating unit contains one copy of each of the five histone genes in the order and orientation mean value of H3 H4 mean value of H2A H2B H1 mean value of. The overall length is 6262 bp. The orientation, nucleotide sequence and inferred amino acid sequence as well as the chromosomal arrangement and localization are different from those reported for Drosophila melanogaster. The codon usage also shows marked differences between Chironomus and Drosophila. Thus the histone gene structure reported for Drosophila is not typical of all insects.

Amino Acid Sequence↗

Subrepeats result from regional DNA sequence conservation in tandem repeats in Chironomus telomeres.

Repeat units, widespread in eukaryotic genomes, are often partially or entirely built up of subrepeats. Homogenization between whole repeat units arranged in tandem usually can best be understood as a result of unequal crossing over. Such a mechanism is less plausible for maintaining similarities between subrepeats within a repeat unit when present in a regular array. In Chironomus telomeres, large blocks of tandemly repeated approximately 350 base-pair units contain two or three pairs of subrepeats with high mutual identities, embedded in linker DNA, non-repetitive within the repeat unit. Measurements of evolutionary base changes in two closely related species, Chironomus tentans and Chironomus pallidivittatus, permit us to conclude that the subrepeat arrangement is best explained as a consequence of regional sequence conservation after an earlier duplication of an ancestral half-unit.

Animals↗

New foldback transposable element TFB1 found in histone genes of the midge Chironomus thummi.

A new Foldback transposable element (TFB1) has been found in the histone H1-H3 intergenic region in the midge Chironomus thummi thummi. TFB1 has long terminal inverted repeats, composed of short, degenerate subrepeats and is flanked by nine or ten base-pair "target site" duplications. TFB1 is present in at least two adjacent histone gene units in Ch. th. thummi, indicating a homogenization of histone gene repeats. The copy number and chromosomal distribution of TFB1 are different in the closely related subspecies Ch. th. thummi and Ch. th. piger. showing that amplification, elimination and transposition of TFB1 have occurred recently during evolution.

Animals↗

Structure of a hemoglobin gene cluster and nucleotide sequence of three hemoglobin genes from the midge Chironomus thummi piger (Diptera, Insecta).

The aquatic larvae of the genus Chironomus (Diptera, Insecta) contain at least 12 different hemoglobin (Hb) variants in their hemolymph. In the present study we have analysed the structure and part of the nucleotide sequence of a Hb gene cluster cloned from the genomic DNA of Chironomus thummi piger. The cluster contains probably 6 different genes, separated by intergenic regions of various lengths. The nucleotide sequence of three putative Hb genes including the intergenic regions is presented. The inferred amino-acid sequences show clearly that two of these putative genes code for subvariants of the Hb variant VIIB. The third gene codes for a so far unknown Hb protein. As known already for other chironomid Hb genes, there are no intron sequences present in the coding regions.

Amino Acid Sequence↗

The nucleotide sequence and in situ localization of a gene for a dimeric haemoglobin from the midge Chironomus thummi piger.

A cluster containing at least four globin genes was isolated by screening an lambda EMBL3 genomic DNA library of the midge Chironomus thummi piger (Ctp) with a heterologous haemoglobin (Hb) gene IV (HbIV) probe from Chironomus thummi thummi (Ctt). This globin gene cluster was localized by in situ hybridization to chromosome II. One globin gene together with its 5'- and 3'-flanking regions has been sequenced. It can be deduced from the sequence that it is a new member of the dimeric HbVIIB family. The Ctp HbVIIB-5 gene displays 91.8% nucleotide sequence homology to a HbVIIB cDNA sequence, reported previously. There is no evidence for intron/exon structure in the Ctp HbVIIB-5 gene.

Amino Acid Sequence↗

Cotransposition of a highly repetitive DNA element with flanking sequences in the genome of the midge Chironomus thummi.

A family of highly repetitive DNA elements, the Cla-elements, is present in the genomes of the two sibling species Chironomus th. thummi and Ch. th. piger. These Cla-elements are organized in large tandem repetitive clusters as well as occurring as interspersed monomeric elements, in both subspecies. The analysis of a monomeric Cla-element and several kilobases of its flanking sequences from Ch. th. piger revealed that the short Cla-elements are cotransposed together with adjacent DNA. We found the same association of Cla-elements with specific flanking DNA in clones obtained from the rDNA of Ch. th. thummi and from nonribosomal Cla-DNA of Ch. th. piger. The Cla-element-flanking DNA is clearly also repetitive, but mainly of interspersed organization.

Animals↗

Clustered and interspersed repetitive DNA sequence family of Chironomus. The nucleotide sequence of the Cla-elements and of various flanking sequences.

The nucleotide sequence of more than 30 cloned members of the clustered and interspersed repetitive Cla-sequence family present in the genome of various chironomids has been determined. In four cloned Cla-element clusters, the 5' and 3'-flanking sequences including the junctions between the Cla-element clusters and the flanking sequences were also sequenced. The repetitive Cla-elements, which are able to transpose under certain circumstances, have a monomer length ranging from 110 to 119 base-pairs, are very A + T-rich (greater than 80% A + T) and display numerous palindromic sequences. The Cla-elements are organized in small (4 elements) to medium-sized (greater than 30 elements) tandem repetitive clusters, which are dispersed over more than 200 sites of the chromosomes of Chironomus thummi thummi, including the non-transcribed spacer of the ribosomal DNA repeating unit. The tandem repetitive Cla-elements show anomalous behaviour during high-percentage polyacrylamide gel electrophoresis, indicating a bent or globular conformation. The flanking sequences are also repetitive, but the sequenced parts did not reveal any tandem repetitive arrangement. Near the junctions of the Cla-element clusters and the flanking sequences, short duplications are found, ranging from 5 to 12 bases, present in both sides of the Cla-element clusters. The Cla-elements might be involved in the hybrid dysgenesis phenomenon that is observed after crossings between the two subspecies Ch. th. thummi and Ch. th. piger.

Animals↗