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Biomedical subjects

L Wieslander

Publications and source records attributed to L Wieslander.

At least 37 records · Page 2Linked to original sources
PubMed1993

Long-term effect of treatment with the headgear-Herbst appliance in the early mixed dentition. Stability or relapse?

In this investigation of the long-term effect of mandibular protrusive function in children with severe Class II malocclusions, a group of children age 8 years 8 months were initially treated for 5 months with a headgear-Herbst appliance followed by a 3- to 5-year period of activator retention. The patients were studied out of retention at the mean age of 17 years 4 months and compared with an untreated control group. Part of the sagittal correction relapsed. As compared with the control group, the average 3.9 mm protrusive effect of treatment on the mandible decreased to a nonsignificant 1.5 mm out of retention. The significant 2.0 mm therapeutic increase of the condylion-gnathion distance decreased to 1.3 mm and was not significantly different from control values at age 17 years 4 months. However, the 1.5 mm posterior effect of treatment on the maxilla continued to increase during activator retention and the difference compared with the control group was 2.3 mm postretention. This effect on the maxilla partly compensated the relapse tendency observed in the mandible so that 3.8 mm of the 5.4 mm posttreatment sagittal improvement still remained out of retention. Because of the sample size and individual variability, the results should be interpreted cautiously, but the findings indicate that maxillary sutural remodeling might be more receptive long-term to orthopedic treatment than the mandibular condylar growth process.

Case-Control Studies↗
PubMed1992

Balbiani ring 1 gene in Chironomus tentans. Sequence organization and dynamics of a coding minisatellite.

Balbiani ring (BR) genes in diptera encode large secretory proteins and are classical model systems for studies of gene expression. In Chironomus tentans, four closely related BR genes, BR 1, BR 2.1, BR 2.2 and BR 6 form a gene family. The BR genes have been partially characterized and are known to contain long arrays of tandemly arranged repeat units with an hierarchical repeat organization. Here, we report the sequence organization of the complete transcribed part of the BR 1 gene in C. tentans. The gene contains five exons and four introns. Three of the introns are located at the 5' end and the fourth at the 3' end of the gene. Exon 4 is approximately 35,000 bases long and is built completely from tandemly organized repeats. We show that this long repeat block contains two types of related repeat units, beta and gamma. Each type forms a large uninterrupted array, a 5' beta array and a 3' gamma array with a sharp border between them. In the hierarchical repeat structure in each repeat array, all repeats are virtually identical at one level of repetition, but shown differences at the next level. The whole repeat block in the BR 1 gene fluctuates in size between different alleles, but not by more than 10%. In contrast, within the block, the beta and gamma arrays vary in length between 8000 and 29,000 bases in an inverse fashion, together keeping the overall length requirement. We propose that the length of exon 4 is conserved by selection of cross-over products of a given length, and that the internal hierarchical sequence organization in the BR 1 gene is a consequence of the combined action of several different sequence turnover mechanisms, all dependent on the unequal pairing of homologous sequences at different, competing levels of repetition.

Amino Acid Sequence↗
PubMed1992

Sequence organization of the Balbiani ring 2.1 gene in Chironomus tentans.

Balbiani rings are giant chromosomal puffs, containing related genes that provide unique possibilities for in vivo analysis of gene expression at the chromatin and ribonucleoprotein levels. Here, the 5' end of the Balbiani ring 2.1 gene in the dipteran Chironomus tentans has been isolated and the sequence organization of the entire Balbiani ring gene is presented. The gene contains five exons, one being extremely small, only 6 base pairs, and one being extremely large, approximately 30 kilobase pairs. Three introns are located at the 5' end and a fourth one is located at the 3' end. The central 30-kilobase-pair exon is entirely built from tandemly organized repeats. All repeats are virtually identical except for a few variant repeats at both ends of the repeat array. The number of repeats may vary between alleles and the length of the gene therefore changes between 30 and 35 kilobase pairs.

Amino Acid Sequence↗
PubMed1992

Secretory proteins of Chironomus salivary glands: structural motifs and assembly characteristics of a novel biopolymer.

Salivary glands of Chironomus synthesize a family of at least ten secretory proteins that can be grouped into three size classes: the large (about 1000 kDa), intermediate (100- to 200 kDa), and small (less than 100 kDa). After synthesis, secretory proteins undergo a dramatic transformation to form a novel biopolymer. Secretory proteins accumulate in the central lumen of the gland, forming dissociable complexes that appear as a network of smooth fibrils and multistranded beaded fibers. When secretory protein complexes are extruded through the secretory duct, the fibers become oriented in parallel arrays; when these parallel arrays of fibers emerge from the mouth of larvae they are an insoluble, silk-like thread. Regulation of secretory protein-coding gene expression determines which secretory proteins are synthesized, thus, the composition of silk threads. At least two types of threads are produced: larval silk is used to construct tubes for protective housing and assist with feeding; prepupal silk is used to construct tubes for larval/pupal ecdysis (pupation). Variations in composition presumably contribute to different mechanical properties of larval and prepupal silk threads. Since the macroscopic physical properties of polymerized silk most likely reflect the microscopic structure and interaction of secretory proteins, it becomes important to learn the principles which govern secretory protein assembly at the molecular level. Which secretory proteins interact and what are the sites used for intraportein and protein-protein interactions during the assembly of this biopolymer? All eight secretory proteins characterized thus far contain tandemly repeated peptide sequences (ranging from 14-90 amino acids in length) and/or a periodic distribution of Cys residues. These motifs appear to be unique; no other biopolymer has either the repeated peptide sequences or composite structure of chironomid silk threads. The evolutionary conservation of motifs within repeats and among different secretory proteins suggests that the sequences and three-dimensional structures of the motifs may be important for assembly of secretory proteins into complexes, oriented fibers, and silk threads. Further study of secretory protein assembly will bring us closer to understanding how this silk assembles in vivo. By learning principles that nature employs to construct such a novel composite biopolymer, it may become feasible to design and produce new classes of fibers or biomolecular materials with distinctive properties that are currently unavailable.

Amino Acid Sequence↗
PubMed1992

Conserved and variable repeat structures in the Balbiani ring gene family in Chironomus tentans.

The four Balbiani ring (BR) genes, BR1, BR2.1, BR2.2, and BR6 in the midge Chironomus tentans constitute a gene family encoding secretory proteins with molecular weights of approximately 10(6) daltons. The major part of each gene is known to consist of tandemly organized composite repeat units resulting in a hierarchic repeat arrangement. Here, we present the sequence organization of the 5' part of the BR2.2 and BR6 genes and describe the entire transcribed part of the two genes. As the BR1 and BR2.1 genes were also fully characterized recently, this allows the comparison of all genes in the BR gene family. All four genes share the same exon-intron structure and have evolved by gene duplications starting from a common ancestor, having the same overall organization as the BR genes of today. The genes encode proteins that have an approximately 10,000-amino acid residue extended central domain, flanked by a highly charged, approximately 200-residue amino-terminal domain and a globular 110-residue carboxy-terminal domain. Exons 1-3 and the beginning of exon 4 encode the amino-terminal domain, which throughout contains many regions built from short repeats. These repeats are often degenerate as to repeat unit and sequence and are present in different numbers between the genes. In several instances these repeat structures, however, are conserved at the protein level where they form positively or negatively charged regions. Each BR gene has a 26-38-kb-long exon 4, which consists of an array of 125-150 repeat units and encodes the central domain. The number of repeat units appears to be largely preserved by selection and all repeat units in the array are very efficiently homogenized. Occasionally variant repeats have been introduced, presumably from another BR gene by gene conversion, and spread within the array. Introns 1-3 at the 5' end of the genes have diverged extensively in sequence and length between the genes. In contrast, intron 4 at the 3' end is virtually identical between three of the four genes, suggesting that gene conversion homogenizes the 3' ends of the genes, but not the 5' ends.

Amino Acid Sequence↗
PubMed1990

[Methods of studying genes and gene function].

In several fields, such as immunology, biochemistry, and structural biology, but particularly in molecular genetics, modern methods enable genes and their protein products to be analysed and described. The tools are now available to study any physiological process or disease at the molecular level. As a result, genetic diseases and viral infections can be better identified and understood. Basic cellular and physiological mechanisms are beginning to be elucidated, the disturbance of which is a factor involved in cancerogenesis, for instance, or the development of hypercholesterolaemia. The article is intended as a brief review of current methods of studying genes and their function. The isolation and characterisation of genes by means of recombinant DNA technology, the identification of defective genes, and the analysis of gene function, both in vitro and in vivo are presented.

Chromosome Mapping↗
PubMed1990

The Balbiani ring 3 gene in Chironomus tentans has a diverged repetitive structure split by many introns.

A set of approximately 15 secretory proteins is synthesized by the salivary gland cells in the midge Chironomus tentans. These proteins are secreted but do not form insoluble fibers until they are transported out of the gland lumen. A Balbiani ring (BR) gene family consisting of four genes (BR1, BR2.1, BR2.2 and BR6) have previously been shown to encode four of these proteins, sp-I a to d, with relative molecular weights of 1 x 10(6). Each BR gene contains an uninterrupted block in which about 100 repeats are tandemly arranged. The repeats are virtually identical and efficient homogenization mechanisms must operate within each block. Here we describe a new BR gene, the BR3 gene, which according to structural similarities may belong to the BR gene family, but at the same time exhibits a strikingly different structure. The gene encodes a 10.9 kb transcript that contains 38 introns and is spliced into a 5.5 kb mRNA. The mRNA is translated into a cysteine-rich 185 kDa major component of the gland secretion. The coding sequence in the gene is built from diverged repeats in which mainly the cysteine codons are preserved and the sequence is split by the introns into 17 to 678-bp long exons. The introns are located at defined positions in relation to the repeat structure. In sharp contrast to the uninterrupted array of identical repeats in the BR1-BR6 genes, the repeats in the BR3 gene are not efficiently homogenized and have diverged extensively from each other. We propose that the splitting of the repeat structure into variable sized exons prevents homogenizations dependent on unequal aligning of homologous sequences.

Amino Acid Sequence↗
PubMed1990

A new member of a secretory protein gene family in the dipteran Chironomus tentans has a variant repeat structure.

We describe the structure of a gene expressed in the salivary gland cells of the dipteran Chironomus tentans and show that it encodes 1 of the approximately 15 secretory proteins exported by the gland cells. This sp115,140 gene consists of approximately 65 copies of a 42-bp sequence in a central uninterrupted core block, surrounded by short nonrepetitive regions. The repeats within the gene are highly similar to each other, but divergent repeats are present in a pattern which suggests that the repeat structure has been remodeled during evolution. The 42-bp repeat in the gene is a simple variant of the more complex repeat unit present in the Balbiani ring genes, encoding four of the other secretory proteins. The structure of the sp115,140 gene suggests that related repeat structures have evolved from a common origin and resulted in the set of genes whose secretory proteins interact in the assembly of the secreted protein fibers.

Amino Acid Sequence↗
PubMed1990

[Soft-tissue profile changes through therapy with the Herbst hinge appliance].

The posttreatment tissue profile changes that can be observed after treatment with the Herbst therapy were investigated in a class II malocclusion mixed dentition group. Profile photographs of two groups of 18 patients were compared. One group was treated with the Herbst appliance, the other served as an untreated control. The treated cases were retained by means of an activator after the active treatment period. After this retention period, new profile photographs were taken and compared to the controls. All treated patients displayed a significant improvement of the soft tissue profile at the end of the active treatment period. After retention a relapse tendency could be observed. Due to the large range of observed treatment effects, no correlation between soft tissue profile and skeletal changes could be found.

Activator Appliances↗
PubMed1989

[Acceleration of orthodontically induced tooth movement through the local application of prostaglandin (PGE1)].

A preliminary study was designed to assess the effect of prostaglandin E1 on tooth movement. In 5 patients palatal attachments were bonded on corresponding upper left and right premolars which were to be extracted later in the course of routine orthodontic treatment. A transpalatal elastic exerted reciprocal force on the teeth. Following local anaesthesia, 0.1 ml of a 0.01% (w/v) PGE1 solution in saline was injected under the mucoperiosteum palatal to the test tooth and 0.1 ml saline palatal to the contralateral control tooth. Injections were repeated at weekly intervals. On average, the PGE1-treated teeth moved 3 times faster than the controls but the rate of movement differed individually. Clinical and x-ray examinations of the teeth involved in the study as well as the surrounding tissues showed no evidence of pathologic changes. No negative side effects were noticed by the patients. Despite positive experiences, this treatment is not to be recommended for use in dental offices yet.

Adolescent↗
PubMed1988

Terminal repeats in long repeat arrays are likely to reflect the early evolution of Balbiani ring genes.

Balbiani ring (BR) genes in Chironomus tentans are 35 to 40 kb (1 kb = 10(3) bases or basepairs) in length and encode secretory proteins of exceptional size. Each gene contains a large homogeneous core block consisting of approximately 100 tandemly arranged, highly homologous repeat units. The repeat unit has a constant (C) region and a subrepeat (SR) region. The various BR genes exhibit similar C regions, while the SR regions differ as to sequence, length and number of subrepeats. To study early steps in the evolution of the coding repeat arrays of the BR genes we have analyzed the 3' ends of the four BR genes in C. tentans: BR1, BR2.1, BR2.2 and BR6. In each gene the very end of the core block consists of two or three repeat unit variants; in each variant repeat the C region is linked to a Cys region, replacing the SR region. Sequence comparisons between the C regions of the closely related BR1 and BR2 genes show that during evolution the terminal repeat unit variants have to a large extent been isolated from the remainder of the core block and have probably been more conserved than the interior repeat units. Detailed analysis of the structure of the variant repeat units further supports this latter notion and suggests that the BR core blocks have evolved from an array of a simple 36 base-pair long sequence; larger, more complex repeat units containing subrepeats were gradually formed and spread in the block, mainly by homologous unequal recombination events. During this evolution the interior of the core blocks evolved as a homogeneous repetitive structure, while ancestor repeat units remained as sequence relicts in the terminal parts.

Animals↗
PubMed1986

A BR 1 gene in Chironomus tentans has a composite structure: a large repetitive core block is separated from a short unrelated 3'-terminal domain by a small intron.

The large Balbiani ring (BR) genes in the dipteran genus Chironomus have been considered to be homogeneous repetitive structures. Analysis of a genomic DNA segment now reveals that a BR 1 gene in C. tentans is a composite gene, consisting of two different types of sequences. A 15-20 kb core block of tandemly arranged repeat units extends close to the 3' end of the BR 1 gene and ends in repetitive structures partly different from the repeat units in the core block. A 55 bp long intron separates the core block, which probably constitutes a single exon, from a non-related 3'-exon, comprising the final 332 bp of the translated part of the gene. According to hydrophobicity and secondary structure predictions, the 3'-exon encoded peptide is distinctly different from the repetitive core block domain and attains a globular structure. The carboxyl-terminal peptide domain is likely to be a general feature of BR encoded proteins and may have important functions in the excretion and polymerisation of the secretory proteins.

Amino Acid Sequence↗
PubMed1985

Detection of IgA heavy chain constant region genes in IgA deficient donors: evidence against gene deletions.

Sixty-six donors with selective IgA deficiency and one patient with selective IgA2 deficiency were investigated for immunoglobulin gene defects using restriction enzyme digestions and Southern blot analysis. All patients carried alpha 1 and alpha 2 genes in their genome, suggesting that large deletions are uncommon causes for IgA deficiency. Digestion with Bam HI, Pst I and Pvu II, did not reveal any polymorphism in the studied samples.

Chromosome Deletion↗
PubMed1984

Conserved and nonconserved structures in the secretory proteins encoded in the Balbiani ring genes of Chironomus tentans.

The large, repetitive Balbiani ring (BR) genes, BR 1, 2, and 6, in Chironomus tentans originated from a short ancestral sequence and have all evolved according to analogous amplification schemes. We analyzed the structures of the BR-encoded secretory proteins and defined the parts that have been conserved during the evolutionary process. The BR products show striking similarities, with the BR 1 and BR 2 products being more similar to each other than to the BR 6 product. In the constant (C) region of the repeat units, 7 of the 30 amino acid residues are strictly conserved; 4 of these are the cysteine residues. The subrepeat (SR) regions of all the BR products are dominated by repeated tripeptide elements rich in proline and charged amino acid residues. Most of the amino acid replacements in both regions are conservative. Secondary structure predictions suggested that the C regions of the BR 1 and BR 2 products have several elements of secondary structure: an alpha-helix, a beta-strand, and one or two reverse turns, as in "globular structures." The prediction for the C region of the BR 6 product is similar but lacks a beta-strand. The predictions for the intervening SR regions appear less conclusive, but are clearly different from those for the C regions, and suggest regular structures not differing in their conformational elements. The SR regions evolved from an ancestor sequence similar to the C region; thus, the BR products seem to represent an example of evolution from one structure to two differently folded products.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗