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PubMed1992

[Successful selective electrical ablation of the retrograde pathway in atrioventricular nodal reentry tachycardia associated with syncope].

A 55-year-old man was admitted to the intensive care unit on account of repeatedly occurring syncopes which developed at the peak of physical exertion. The attack was reproduced by exercise on a bicycle ergometer: the patient developed paroxysmal tachycardia with a narrow QRS and a frequency of 160/min leading after 20 sec. to severe hypotension and loss of consciousness. The same tachycardia caused by programmed atrial stimulation caused a drop of tension in the recumbent position by 30 mmHg and after more detailed analysis during electrophysiological examination it was evaluated as atrioventricular nodal reentrant tachycardia. By an electric discharge of 300 J administered by means of a stimulation electrode 7F USCI into the area of the AV node the retrograde conduction through the perinodal rapid pathways was completely interrupted and 1st. degree atrioventricular block developed. Repeated electrophysiological examination and exercise tests on a bicycle ergometer provided evidence of the disappearance of the retrograde pathway and the impossibility to elicit AVNRT. The authors express the view that the rapid perinodal pathway is interrupted in successful cases in both directions and the 1st. degree AV block is due to conduction along a slow pathway and not incidental slowing of conduction along the rapid pathway which is the generally accepted interpretation. Modification of the atrioventricular conduction by interruption of the rapid pathway by fulguration is according to data in the literature and the described patient a method which makes is possible to cure severe atrioventricular nodal reentrant tachycardias.

Electrocoagulation↗
PubMed2001

Length of uninterrupted repeats determines instability at the unstable mouse expanded simple tandem repeat family MMS10 derived from independent SINE B1 elements.

Mouse expanded simple tandem repeats (ESTRs) provide highly informative loci for analyzing spontaneous and induced germline mutation. We have conducted an extensive sequence database search and identified 17 new members of the highly unstable rodent-specific ESTR family called MMS10. This family has arisen by independent expansions of a common GGCAGA repeat unit from within a subset of both ancestral and modern SINE B1 elements during the course of mouse evolution. Analysis of the interspersion patterns of variant repeats along alleles of 20 of these MMS10 loci revealed two distinct classes of tandem arrays: one composed of uninterrupted GGCAGA repeats and the second with generally larger arrays interrupted by variant units. Surveys of allelic diversity at 11 representative members of these two classes of loci in various laboratory strains and BXD recombinant inbred lines revealed that the level of repeat instability was positively correlated with the length of uninterrupted repeats. Turnover processes at MMS10 loci, therefore, appear similar to the type of mechanism observed at human microsatellites. The MMS10 family thus provides a potentially useful murine model for studying dynamic mutation at simple tandem repeats.

Alleles↗
PubMed1999

Clustered adenine/thymine stretches are essential for function of a fission yeast replication origin.

We have determined functional elements required for autonomous replication of the Schizosaccharomyces pombe ars2004 that acts as an intrinsic chromosomal replication origin. Internal deletion analysis of a 940-bp fragment (ars2004M) showed three regions, I to III, to be required for autonomously replicating sequence (ARS) activity. Eight-base-pair substitutions in the 40-bp region I, composed of arrays of adenines on a DNA strand, resulted in a great reduction of ARS activity. Substitutions of region I with synthetic sequences showed that no specific sequence but rather repeats of three or more consecutive adenines or thymines, without interruption by guanine or cytosine, are required for the ARS activity. The 65-bp region III contains 11 repeats of the AAAAT sequence, while the 165-bp region II has short adenine or thymine stretches and a guanine- and cytosine-rich region which enhances ARS activity. All three regions in ars2004M can be replaced with 40-bp poly(dA/dT) fragments without reduction of ARS activity. Although spacer regions in the ars2004M enhance ARS activity, all could be deleted when an 40-bp poly(dA/dT) fragment was added in place of region I. Our results suggest that the origin activity of fission yeast replicators depends on the number of adenine/thymine stretches, the extent of their clustering, and presence of certain replication-enhancing elements.

AT Rich Sequence↗
PubMed1996

Evaluation of a new interrupter device for measuring bronchial responsiveness and the response to bronchodilator in 3 year old children.

The interrupter technique for measuring airway resistance is non-invasive and convenient, and therefore ideally suited for the assessment of induced changes in airway calibre in preschool children. The aim of this study was to evaluate a commercially available interrupter device (based on Microlab 4000), which calculates the interrupter resistance (Rint) from pressure and flow following a brief interruption of expiration during quiet breathing. The repeatability of Rint was assessed, and its response to methacholine challenge and the bronchodilator salbutamol were compared with an indirect technique, the fall in transcutaneous oxygen tension (Ptc,O2), using the sensitivity index (SI, i.e. the change after challenge expressed in multiples of the baseline standard deviation) in 12 wheezy children (aged 3 yrs +/- 2 months). The mean (SD) baseline value of Rint was 0.91 (0.20) kPa.L-1.s. Short-term repeatability and baseline variability were satisfactory for Rint (intraclass correlation coefficient = 0.6; mean intrasubject coefficient of variation = 13%). Although 10 of the 12 subjects obtained a significant response using Rint at maximal bronchoconstriction (i.e. SI > 2), overall, Rint was five times less sensitive than Ptc,O2 (geometric mean SI: Rint 3 vs Ptc,O2 16; p < 0.0001). Reversal of obstruction with administration of a bronchodilator was clearly demonstrated in almost all subjects: Rint after challenge (mean +/- SD) 1.25 (0.22) kPa.L-1.s; after salbutamol 0.78 (0.19) kPa.L-1.s; p < 0.001. In conclusion, the convenient interrupter resistance method appears more promising for detecting bronchodilator responses than induced bronchoconstriction in wheezy preschool children; however, measurement of transcutaneous oxygen tension provides a reliable indirect means of detecting induced airway obstruction in this age-group.

Airway Resistance↗
PubMed1976

Prenatal diagnosis of hemoglobinopathies. A review of 15 cases.

We attempted prenatal diagnosis of hemoglobinopathies in 15 cases--11 for beta-thalassemia and four for sickle-cell disease. Fetoscopy was used in seven cases, and placental aspiration in eight. One premature labor, with fetal loss, followed placental aspiration. Globin synthesis was assessed by incubation of samples with 3H-leucine and chain separation on carboxymethylcellulose columns. Homozygous disease was predicted in two pregnancies, which were interrupted, and the diagnosis confirmed. In one case homozygosity was suspected. A repeat test was advised but not accepted. The fetus had thalassemia trait. One pregnancy was interrupted despite our prediction of thalassemia trait. Eight pregnancies went to term. Seven predictions that the infants would not have homozygous disease were confirmed. One prediction of sickle trait proved to be sickle-cell disease. Although prenatal diagnosis of hemoglobinopathies is feasible, the present frequency of fetal loss and diagnostic error indicates need for improvement.

Anemia, Sickle Cell↗
PubMed2004

Resistance to the impact of interruptions during multitasking by healthy adults and dysexecutive patients.

Two experiments (one with healthy adult volunteers and the other with controls and dysexecutive patients) assessed the impact of interruptions on a novel test of multitasking. The test involved switching repeatedly between four tasks (block construction, bead threading, paper folding, alphabetical searching) over a 10 min period. In Experiment 1, there were four groups of 20 healthy participants. One group attempted multitasking with no interruption, a second group was interrupted early in the test, a third group late in the test and a fourth group was interrupted both early and late. Interruption involved carrying out a fifth, unexpected task for a period of 1 min before returning to the four main tasks. There was no difference in multitasking performance between the groups. In Experiment 2 the participants were seven dysexecutive patients and 14 age-matched controls. A repeated measures approach was employed to assess the impact of two interruptions (early and late) for both groups. Contrary to predictions, the patients as well as controls were resistant to the effects of interruptions, despite their clearly impaired multitasking performance. These results suggest that the ability to deal with interruptions may be separable from the ability to organise and execute multiple tasks within a limited time frame.

Adult↗
PubMed1995

Evidence for insertion of a new intron into an Mhc gene of perch-like fish.

The evolution of the major histocompatibility complex (Mhc) has been studied to understand the origin of the immune system, of which it constitutes an essential part. In the present study, the Mhc is used to shed light on questions regarding the origin of introns and the phylogeny of fishes. The organization of the coding (exon) and non-coding (intron) regions of both class I and class II major histocompatibility complex (Mhc) genes is highly conserved in all vertebrate classes; the only variation observed until now is in the number of exons encoding the membrane-anchoring part. Moreover, there is a good correspondence between the exon-intron organization at the DNA level and the division into structurally and functionally defined domains at the protein level. Here we describe the first major exception to this uniformity. The immunoglobulin-like domain of the class II beta-chains in perch-like fishes (Percomorpha) is not encoded in one exon, as it is in all other vertebrates studied thus far, but in two exons. The length of the extra intron varies from gene to gene and from species to species, but is generally less than 200 base pairs (b.p.). Only one of the sequenced introns is about 500 b.p. long. In some of the genes, the intron contains a hexamer repeat. The repeat is present in the transcript at the site at which the intron interrupts exon 3 in the genomic DNA. The intron may therefore have arisen by repeated tandem duplication of this sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Intervening sequences in the ribosomal RNA genes of Ascaris lumbricoides: DNA sequences at junctions and genomic organization.

An rDNA size class in the genome of the nematode Ascaris lumbricoides is described which is interrupted by a 4.5-kb long intervening sequence located in the 26S coding region. This molecular form occurs in approximately 15 copies per haploid genome and amounts to approximately 5% of the total nuclear rDNA. Intervening sequences are present only in the 8.8-kb rDNA, but not in the 8.4-kb rDNA repeating units of A. lumbricoides. Cloning of the interrupted rDNA units revealed, in addition to the main 4.5-kb insertion, shorter intervening sequences of 4-kb and 119-bp length. Both shorter rDNA forms are present in the single copy range of the haploid genome. Sequence analyses of the intervening sequence/rDNA junctions show an identical right-hand junction for all of the three different rDNA forms. The two shorter intervening sequences are a coterminal subset of the right-hand end of the main 4.5-kb insertion, whereas all three insertions have a different left-hand junction with the coding region of rDNA. Each intervening sequence is flanked by a short direct repeat of variable length, being only once present in the uninterrupted rDNA. The intervening sequences of A. lumbricoides show striking similarity to the organization of type I insertion family in dipteran flies, even though they are inserted at different positions in the 26S coding region. Additional rDNA intervening sequences may be present outside of the rDNA cluster, but in not more than 15-20 homologous copies per haploid genome.

Animals↗
PubMed2004

Composition and structure of the centromeric region of rice chromosome 8.

Understanding the organization of eukaryotic centromeres has both fundamental and applied importance because of their roles in chromosome segregation, karyotypic stability, and artificial chromosome-based cloning and expression vectors. Using clone-by-clone sequencing methodology, we obtained the complete genomic sequence of the centromeric region of rice (Oryza sativa) chromosome 8. Analysis of 1.97 Mb of contiguous nucleotide sequence revealed three large clusters of CentO satellite repeats (68.5 kb of 155-bp repeats) and >220 transposable element (TE)-related sequences; together, these account for approximately 60% of this centromeric region. The 155-bp repeats were tandemly arrayed head to tail within the clusters, which had different orientations and were interrupted by TE-related sequences. The individual 155-bp CentO satellite repeats showed frequent transitions and transversions at eight nucleotide positions. The 40 TE elements with highly conserved sequences were mostly gypsy-type retrotransposons. Furthermore, 48 genes, showing high BLAST homology to known proteins or to rice full-length cDNAs, were predicted within the region; some were close to the CentO clusters. We then performed a genome-wide survey of the sequences and organization of CentO and RIRE7 families. Our study provides the complete sequence of a centromeric region from either plants or animals and likely will provide insight into the evolutionary and functional analysis of plant centromeres.

Base Composition↗
PubMed1985

Clinical data for radiation embryology. Investigation programme 1967, report 1984.

In 1967 a prospective clinical study was started with the aim of providing optimum counselling for married couples who desire continuation of a pregnancy despite radiation exposure at an early stage as a result of X-ray diagnostics. Recommendations were devised as to whether an interruption of pregnancy should be applied for or not. These results were discussed repeatedly. Within the framework of the prospective study, embryological examinations were made in cases of interruption of pregnancy, and clinical and genetic examinations in cases of children who had been subject to radiation stress in utero. Up to July 1st 1984 nearly 200 cases of consultations have been or are being surveyed. The children were subjected to selected longterm examinations of up to 13 years. The results of cytogenetic, biochemical-genetic, clinical, and other examinations are considered and special characteristics of interesting cases are discussed. The conclusion was drawn that the recommendation to our patients to continue pregnancy in cases of exposure to radiation in utero below 0.1 Sv, was right. Furthermore the question arose of whether this dose limit could be increased. The study will be continued.

Abnormalities, Radiation-Induced↗
PubMed1997

Molecular cloning of the bovine alpha 1(IV) procollagen gene (COL4A1) and its use in investigating the regulation of expression of type IV procollagen by retinoic acid in bovine lens epithelial cells.

This report is the first to describe the isolation of a 400 base pair cDNA clone encoding part of the bovine alpha 1(IV) procollagen. Using the polymerase chain reaction (PCR), we have amplified a sequence of approximately 400 bp from this gene within the recombinant phage DNA. The cloned sequence encodes 94 amino acids that form part of the protein's helical region. The sequence contains one interruption in the Gly-Xaa-Yaa repeat unit. The third base of the codon for glycine at several sites differs from those seen in murine and human genes, as does the third base of proline codons. The bovine cDNA also contains fewer thymine residues. Northern blot hybridization has shown that the mRNA for bovine procollagen to be 6.2 kb in size. We have used the cDNA clone to investigate the effect of all-trans retinoic acid (RA) on the gene expression of alpha 1(IV) procollagen in cultured bovine lens epithelial (LE) cells. We have also observed that RA decreases total protein production and concomitantly increases type IV procollagen in a concentration dependent manner. An increase in alpha 1(IV)mRNA as well as increase in type IV procollagen suggest that the regulation of alpha 1(IV) gene by RA in the LE cells is at the transcriptional level. Further, our results support the hypothesis that RA inhibition of lens epithelium transformation to fibroblast-like cells may be due to the ability of RA to stimulate the production of basement membrane components by epithelia.

Amino Acid Sequence↗
PubMed1993

cDNA cloning and chromosomal mapping of the mouse type VII collagen gene (Col7a1): evidence for rapid evolutionary divergence of the gene.

Type VII collagen is the major component of anchoring fibrils, critical attachment structures at the dermal-epidermal basement membrane zone. Genetic linkage analyses with recently cloned human type VII collagen cDNAs have indicated that the corresponding gene, COL7A1, is the candidate gene in the dystrophic forms of epidermolysis bullosa. To gain insight into the evolutionary conservation of COL7A1, in this study we have isolated mouse type VII collagen cDNAs by screening a mouse epidermal keratinocyte cDNA library with a human COL7A1 cDNA. Two overlapping mouse cDNAs were isolated, and Northern hybridization of mouse epidermal keratinocyte RNA with one of them revealed the presence of a mRNA transcript of approximately 9.5 kb, the approximate size of the human COL7A1 mRNA. Nucleotide sequencing of the mouse cDNAs revealed a 2760-bp open reading frame that encodes the 5' half of the collagenous domain and a segment of the NC-1, the noncollagenous amino-terminal domain of type VII collagen. Comparison of the mouse amino acid sequences with the corresponding human sequences deduced from cDNAs revealed 82.5% identity. The evolutionary divergence of the gene was relatively rapid in comparison to other collagen genes. Despite the high degree of sequence variation, several sequences, including the size and the position of noncollagenous imperfections and interruptions within the Gly-X-Y repeat sequence, were precisely conserved. Finally, the mouse Col7a1 gene was located by interspecific backcross mapping to mouse Chromosome 9, a region that corresponds to human chromosome 3p21, the position of human COL7A1. This assignment confirms and extends the relationship between the mouse and the human chromosomes in this region of the genome.

Amino Acid Sequence↗
PubMed1991

Primary mesenchyme cells of the sea urchin embryo require an autonomously produced, nonfibrillar collagen for spiculogenesis.

A collagen molecule in the sea urchin embryo was characterized by analysis of a 2.7-kb cDNA clone. This clone, Spcoll, was obtained by screening a gastrula stage Strongylocentrotus purpuratus cDNA library with a 237-bp genomic clone encoding a collagen-like sequence previously isolated by Venkatesan et al. (1986). DNA sequence analysis of the cDNA clone demonstrated the nonfibrillar nature of the encoded molecule--13 interruptions of the Gly-X-Y repeat motif were found in the 85-kDa open reading frame. The mRNA of approximately 9 kb accumulated specifically in mesenchyme cells of the embryo through development to the pluteus larva. Polyclonal antibodies generated against a Spcoll-beta-galactosidase fusion protein were utilized to identify and localize the native Spcoll. This collagen molecule of approximately 210 kDa was deposited into the blastocoel by the primary mesenchyme cells. When primary mesenchyme cells were cultured in vitro, Spcoll was secreted into the media and accumulated at sites of cell-substrate interaction. Addition of anti-Spcoll antibodies to primary mesenchyme cell cultures selectively inhibited spiculogenesis, whereas other antibodies had no inhibitory effect. Since collagen is not a component of the organic matrix of spicules (Benson et al., 1986), these results suggest that the autonomous production of Spcoll by differentiating mesenchyme cells in turn influences the point in differentiation at which these cell initiate biomineralization.

Amino Acid Sequence↗
PubMed1988

Habituation and dishabituation to repeated mild cold exposures in C57BL/6J mice.

Every two weeks for 12 weeks four groups of C57BL/6J male mice, initially 12 months old, were subjected to three-hour cold stress tests, which consisted of a partial physical restraint at an ambient temperature of 10 degrees C. The control group experienced six consecutive tests; one experimental group skipped the cold exposure during test No. 4 but was physically restrained at room temperature; the other two experimental groups omitted test No. 4. One of these groups spent the four weeks between test No. 3 and test No. 5 in their home cages, while the other was subjected to daily, 30-minute sessions of electrical stimulation of the hypothalamus through electrodes implanted in the "rewarding" area of the medial forebrain bundle. All animals in this group showed self-stimulating behavior in the test session which preceded cold stress test No. 1. During test No. 3, all four groups showed an improvement of cold tolerance relative to their first tests; body mass and colonic temperature prior to cold exposure remained unchanged. The two experimental groups that were not exposed to cold during test No. 4 and did not receive brain stimulation, demonstrated a significant worsening of cold tolerance during the subsequent test. Their body mass and baseline colonic temperatures did not change. The control group and the group which was subjected to brain stimulation during the interval between tests No. 3 and No. 5 did not demonstrate any changes in cold tolerance. These data demonstrated habituation to repeated mild cold exposures and dishabituation after interruption of cold exposures.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1982

Cloning yeast telomeres on linear plasmid vectors.

We have constructed a linear yeast plasmid by joining fragments from the termini of Tetrahymena ribosomal DNA to a yeast vector. Structural features of the terminus region of the Tetrahymena rDNA plasmid maintained in the yeast linear plasmid include a set of specifically placed single-strand interruptions within the cluster of hexanucleotide (C4A2) repeat units. An artificially constructed hairpin terminus was unable to stabilize a linear plasmid in yeast. The fact that yeast can recognize and use DNA ends from the distantly related organism Tetrahymena suggests that the structural features required for telomere replication and resolution have been highly conserved in evolution. The linear plasmid was used as a vector to clone chromosomal telomeres from yeast. One Tetrahymena end was removed by restriction digestion, and yeast fragments that could function as an end on a linear plasmid were selected. Restriction mapping and hybridization analysis demonstrated that these fragments were yeast telomeres, and suggested that all yeast chromosomes might have a common telomere sequence. Yeast telomeres appear to be similar in structure to the rDNA of Tetrahymena, in which specific nicks or gaps are present within a simple repeated sequence near the terminus of the DNA.

Animals↗
PubMed1991

A simple and multi-purpose "concentration-clamp" method for rapid superfusion.

A simple method for the rapid exchange of the medium used for a variety of electrophysiological experiments including patch-clamp experiments on cultured cells is described. The advantages of this method over the conventional ones are that this solution exchange system has a very simple structure and thus is inexpensive and can be easily installed in already existing experimental setups. The method involves the use of a fine double-barrelled polyethylene needle placed near the cell or other isolated preparations under recording. Electromagnetic valves are used to switch the solutions in the polyethylene tubes which enable a rapid and localized application of test solutions as well as their rapid washout. The latency of solution exchange, as measured by a change in the holding current under voltage-clamp experiments was fairly rapid (about 120 ms). Neither was the recording interrupted nor the sealing resistance affected during repeated exposure to test solutions. This method is proving to be useful, particularly for electrophysiological and pharmacological studies on immovable cells such as those in culture.

Animals↗
PubMed1986

Isolation of an alpha 1 type-IV collagen cDNA clone using a synthetic oligodeoxynucleotide.

We have isolated a cDNA clone (pCIV-1-225) for the alpha 1 subunit of basement membrane (type IV) collagen from a cDNA library made from Engelbreth-Holm-Swarm mouse tumor RNA. The cDNA library was screened with synthetic oligodeoxynucleotides derived from published amino acid (aa) sequences (Schuppan et al., 1982). Nucleotide sequence data established the identity of our cDNA clone to encode an alpha 1 type IV collagen. This clone contains 270 aa of the helical region and has three interruptions in the Gly-X-Y repeat unit.

Amino Acid Sequence↗
PubMed2001

Hypoxic enhancement of type IV collagen secretion accelerates adipose conversion of 3T3-L1 fibroblasts.

Hypoxic modulation of collagen metabolism appears to be related to pathogenesis of many diseases such as fibrosis of connective tissue after injury and scleroderma. Since most of our understanding of how procollagen assembles within the cell has come from studies on cells cultured under normoxia, it may not be helpful for the etiology of the diseases observed in peripheral tissues under hypoxic conditions. As an experimental model for the hypoxic modulation of collagen metabolism, we cultured 3T3-L1 fibroblasts under low partial oxygen pressure and found that hypoxia enhances secretion of type IV collagen 10-fold and accelerates adipose conversion of the cells. The enhanced secretion of type IV collagen was not accompanied by an appreciable increase of alpha1(IV) and alpha2(IV) mRNAs. Prolyl 4-hydroxylase alpha increased only 3-fold under hypoxia. We suggest that hypoxia creates an environment of prolyl 4-hydroxylase alpha(2)beta(2) tetramers favorable for the folding of type IV procollagen which has many interruptions of the Gly-Xaa-Yaa repeat.

3T3 Cells↗