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C Larsson

Publications and source records attributed to C Larsson.

At least 253 records · Page 14Linked to original sources
PubMed1995

Mutations of codon 918 in the RET proto-oncogene correlate to poor prognosis in sporadic medullary thyroid carcinomas.

The hereditary multiple endocrine neoplasia syndromes types 2A and B (MEN 2A and B) were recently linked to germline mutations in the RET proto-oncogene, altering one of five cysteine residues in exon 10 or 11 (MEN 2A), or substituting a methionine for a threonine at codon 918 in exon 16 (MEN 2B). The latter mutation also occurs somatically in some sporadic medullary thyroid carcinomas (MTC), and has in a previous study been correlated with a less favorable clinical outcome. In the present study, 46 MTCs were selected for investigation of the codon 918 mutation. The mutation was found in 29 tumors (63%), and was significantly correlated with a poor outcome, with regard to distant metastasis or tumor recurrence (p < 10(-4)). Two tumors showed multifocal growth and C-cell hyperplasia, and these patients were therefore also investigated for germline mutations in exons 10, 11 and 16. The codon 918 mutation was found only in the tumors, thus of somatic origin. The RET codon 918 mutation may have prognostic impact, and therefore preoperative assessment may influence decision-making in the treatment of patients suffering from MTC.

Base Sequence↗
PubMed1995

A murine replication protein accumulates temporarily in the heterochromatic regions of nuclei prior to initiation of DNA replication.

We have analyzed the expression of the murine P1 gene, the mammalian homologue of the yeast MCM3 protein, during the mitotic cell cycle. The MCM3 protein has previously been shown to be of importance for initiation of DNA replication in Saccharomyces cerevisiae. We found that the murine P1 protein was present in the nuclei of mammalian cells throughout interphase of the cell cycle. This is in contrast to the MCM3 protein, which is located in the nuclei of yeast cells only between the M and the S phase of the cell cycle. Detailed analysis of the intranuclear localization of the P1 protein during the cell cycle revealed that it accumulates transiently in the heterochromatic regions towards the end of G1. The accumulation of the P1 protein in the heterochromatic regions prior to activation of DNA replication suggests that the mammalian P1 protein is also of importance for initiation of DNA replication. The MCM2-3.5 proteins have been suggested to represent yeast equivalents of a hypothetical replication licensing factor initially described in Xenopus. Our data support this model and indicate that the murine P1 protein could function as replication licensing factor. The chromosomal localization of the P1 gene was determined by fluorescence in situ hybridization to region 6p12 in human metaphase chromosomes.

3T3 Cells↗
PubMed1995

Sequence-specific purification of nucleic acids by PNA-controlled hybrid selection.

Using an oligohistidine peptide nucleic acids (oligohistidine-PNA) chimera, we have developed a rapid hybrid selection method that allows efficient, sequence-specific purification of a target nucleic acid. The method exploits two fundamental features of PNA. First, that PNA binds with high affinity and specificity to its complementary nucleic acid. Second, that amino acids are easily attached to the PNA oligomer during synthesis. We show that a (His)6-PNA chimera exhibits strong binding to chelated Ni2+ ions without compromising its native PNA hybridization properties. We further show that these characteristics allow the (His)6-PNA/DNA complex to be purified by the well-established method of metal ion affinity chromatography using a Ni(2+)-NTA (nitrilotriactic acid) resin. Specificity and efficiency are the touchstones of any nucleic acid purification scheme. We show that the specificity of the (His)6-PNA selection approach is such that oligonucleotides differing by only a single nucleotide can be selectively purified. We also show that large RNAs (2224 nucleotides) can be captured with high efficiency by using multiple (His)6-PNA probes. PNA can hybridize to nucleic acids in low-salt concentrations that destabilize native nucleic acid structures. We demonstrate that this property of PNA can be utilized to purify an oligonucleotide in which the target sequence forms part of an intramolecular stem/loop structure.

Base Composition↗
PubMed1995

Rearrangement of proximal 11q13 band in a CMML in acute transformation.

Fluorescence in situ hybridization (FISH) was performed on bone marrow cells thought to contain a t(7;11)(p22;q13) from a patient with chronic myelomonocytic leukemia in transformation. FISH analysis using a panel of 10 probes previously mapped to 11q13 revealed a cytogenetically undetected complex rearrangement that involved chromosomes 7 and 11 as well as a chromosome 3 at band p24. Two distinct translocation breakpoints, both proximal to the BCL1 locus, were found in chromosome 11 that perforce separate it into three subregions. The two breakpoints appear distinct from the two previously described ones which involved the FAU and GSTP1 genes. Our observations add to the involvement of proximal 11q13 in myeloid malignancies.

Acute Disease↗
PubMed1995

Familial periodic cerebellar ataxia without myokymia maps to a 19-cM region on 19p13.

Familial periodic cerebellar ataxia (FPCA) is a heterogeneous group of rare autosomal dominant disorders characterized by episodic cerebellar disturbance. A potassium-channel gene (KCNA1) has been found to be responsible for one of its subgroups, familial periodic cerebellar ataxia with myokymia (FPCA/+M; MIM 160120). A different subgroup that is not associated with myokymia (FPCA/-M; MIM 108500) was recently mapped to chromosome 19p. Here we have performed linkage analysis in two large families with FPCA/-M that also demonstrated neurodegenerative pathology of the cerebellum. Three markers in 19p13 gave significant lod scores (> 3.0), while linkage to KCNA1 and three known loci for spinocerebellar ataxia (SCA1, SCA2, and SCA3) was excluded. The highest lod score was obtained with the marker D19S413 (4.4 at recombination fraction 0), and identification of meiotic recombinants in affected individuals placed the locus between the flanking markers D19S406 and D19S226, narrowing the interval to 19 cM. A CAG trinucleotide-repeat expansion was detected in one family but did not cosegregate with the disease.

Cerebellar Ataxia↗
PubMed1995

CT assessment of subarachnoid haemorrhage. A comparison between different CT methods of grading subarachnoid haemorrhage.

A number of different CT classifications of subarachnoid haemorrhage (SAH) were applied to a consecutive series of 50 patients with aneurysmal SAH. The best correlation with delayed ischaemic deficits (DID) was obtained with a score formed by the sum of the individual cisternal grades except that of the cortical subarachnoid space. The findings emphasize the significance of the extent of the SAH, rather than the presence of a localized cisternal clot with regard to the development of DID.

Aneurysm, Ruptured↗
PubMed1994

The human NOTCH1, 2, and 3 genes are located at chromosome positions 9q34, 1p13-p11, and 19p13.2-p13.1 in regions of neoplasia-associated translocation.

In Drosophila the Notch gene controls differentiation to various cell fates in many tissues. Three mammalian Notch homologs have recently been identified: Notch 1, 2, and 3. All three homologs are very highly conserved relative to the Drosophila Notch gene, which suggests that they are important for cell differentiation in mammals. This notion is supported by the previous finding of a truncated, translocated form of the human NOTCH1 gene (formerly TAN1) in three cases of leukemia. Given this genetic link between NOTCH1 and tumor formation, it is of interest to establish the chromosomal positions of the other two homologs. We report the identification of cosmid clones for the human NOTCH1, 2, and 3 genes. These clones were used as probes in fluorescence in situ hybridization to human metaphase chromosomes, and the results, combined with data from somatic cell hybrid panels, show that the NOTCH2 and 3 genes are located at positions 1p13-p11 and 19p13.2-p13.1, respectively, which are regions of neoplasia-associated translocation.

Amino Acid Sequence↗
PubMed1994

Activation of the Ig germ-line gamma 1 promoter. Involvement of C/enhancer-binding protein transcription factors and their possible interaction with an NF-IL-4 site.

Ig isotype switching in B lymphocytes is preceded by transcription of the corresponding unrearranged, or germ-line (GL), CH gene. The promoter of mouse GL C gamma 1 transcripts has been shown to be located within a 349-bp KpnI/Bg/II fragment, extending from -147 to +202 bp relative to the first transcription initiation site. By the electrophoretic mobility shift assay, we have analyzed nuclear extracts from three B cell lines and splenic B cells for the presence of proteins binding to this fragment. We show that they give different patterns of DNA binding, implying significant complexity in the regulation of this locus. We focused on the sIgM+ mouse B lymphoma line L10A6.2 that has been shown able to confer responsiveness of the GL gamma 1 promoter to phorbol ester plus IL-4. Activation of this cell line results in altered expression of several nuclear DNA-binding complexes involving two members of the C/enhancer-binding protein (EBP) family of transcription factors, namely C/EBP beta (nuclear factor (NF)-IL-6/LAP) and Ig/EBP-1 (C/EBP gamma). The complexes bind to two C/EBP elements, one at about -115 bp and one near the first RNA start site. In normal B cells stimulated by LPS or IL-4, new complexes appear that bind to C/EBP and NF-IL-4 elements, respectively, located within the -125/-101 region. The -125/-101 segment previously has been shown to be required for transcriptional activation. We discuss these findings in relation to the presence of consensus C/EBP binding sites in other IL-4-regulated promoters.

Animals↗
PubMed1994

Mechanisms of muscarinic receptor-stimulated expression of c-fos in SH-SY5Y cells.

In this study, the signal cascade transducing carbachol stimulation into c-fos expression in SH-SY5Y neuroblastoma cells was investigated. 1,2-Diacylglycerol formation and c-fos expression were mediated via stimulation of muscarinic M1 receptors and the first 5 min of receptor stimulation were critical for these events. Application of 1,2-dioctanoylglycerol induced c-fos expression and this, as well as carbachol-stimulated c-fos expression, was inhibited by protein kinase C inhibitors. Increasing the intracellular Ca2+ concentration had only small effects on c-fos expression. There was a dependency on extracellular Ca2+ for maximal c-fos expression and 1,2-diacylglycerol formation. The carbachol-stimulated c-fos expression was potentiated by application of the protein phosphatase inhibitor okadaic acid. These results demonstrate the importance of 1,2-diacylglycerol formation for muscarinic receptor-stimulated, protein kinase C-mediated c-fos expression in the SH-SY5Y cells and that this cascade is counteracted by an okadaic acid-sensitive protein phosphatase.

Carbachol↗
PubMed1994

Characterization of the chromosomal gene and promoter for human insulin-like growth factor binding protein-5.

To better understand the regulation of insulin-like growth factor binding protein-5 (IGFBP-5) expression, we cloned the IGFBP-5 gene from human genomic libraries and identified a region in the 5' flanking sequence which functions as a promoter. The human IGFBP-5 gene is divided into four exons which, primarily due to a first intron of approximately 25 kilobases, span approximately 33 kilobases of DNA. Southern analysis identified a single copy of the IGFBP-5 gene in the haploid human genome, and several independent mapping strategies found this gene tightly linked with, and in opposite transcriptional orientation to, the IGFBP-2 gene at chromosomal region 2q33-34. Primer extension studies identified the IGFBP-5 mRNA cap site 772 base pairs (bp) 5' to the first nucleotide of the translation start codon. Analysis of the 5'-flanking sequence identified a potential TATA element beginning 33 bp 5' to the mRNA cap site. When a DNA fragment containing this cap site and 461 bp of upstream sequence was placed 5' to the chloramphenicol acetyltransferase reporter gene and transfected into MDA-MB-468 human breast cancer cells, it directed chloramphenicol acetyltransferase expression in an orientation-specific manner, suggesting that this region contains elements essential for IGFBP-5 promoter activity.

Amino Acid Sequence↗
PubMed1994

Effects of morphine on prolactin receptors in the rat brain.

The effect of chronically given morphine on the binding of ovine prolactin (oPRL) to specific areas in the male rat brain was studied. The drug was delivered through subcutaneously implanted miniosmotic pumps. The results indicated that the density of prolactin binding sites in the hypothalamus and the choroid plexus was significantly decreased in the acute phase of morphine administration but restored to control levels when tolerance to morphine was developed. The decrease in prolactin binding was contrasted by elevated plasma levels of the hormone. A negative correlation was found between the hormone concentration in plasma and the density of its binding sites in the hypothalamus and choroid plexus. The hormone-binding sites in these two regions were further characterized with regard to binding constants and molecular sizes. The relevance of the present results with respect to the hypothalamic control of prolactin secretion is discussed.

Animals↗
PubMed1994

Fine mapping of Best's macular dystrophy localizes the gene in close proximity to but distinct from the D11S480/ROM1 loci.

The Best's macular dystrophy (BMD) gene has previously been mapped to the 11q13 region. In this study, recombination data localizes the BMD gene to the 6-cM genetic interval between the markers Fc epsilon RI and D11S480/ROM1 in a large Swedish 12-generation BMD family. Mutation analyses of the candidate gene ROM1 did not reveal any mutations that could explain the disease phenotype. However, one recombination event between intragenic ROM1 polymorphisms and the BMD phenotype was detected. Therefore, it is highly unlikely that mutations in the ROM1 gene cause BMD. Identification of the disease gene will elucidate the pathophysiological mechanism in BMD, which may also be of importance in other retinopathies such as age-related macular degeneration.

Alleles↗
PubMed1994

Adaptation of signal transduction in brain.

Cell culture models were used to study the effects of long-term ethanol exposure on neuronal cells. Effects on phospholipase C and phospholipase D mediated signal transduction were investigated by assaying receptor-binding, G protein function, activities of lipases, formation of second messengers and c-fos mRNA. The signal transduction cascades displayed abnormal activities from 2 to 7 days of exposure which differed from the acute effects. Phosphatidylethanol formed by phospholipase D is an abnormal lipid that may harmfully affect nerve cell function.

Acclimatization↗
PubMed1994

Bone response to surface modified titanium implants: studies on electropolished implants with different oxide thicknesses and morphology.

In a series of experimental studies, bone formation was analysed around systematically modified titanium implants. In the present study, machined, electropolished and anodically oxidized implants were prepared, surface characterized and inserted in the cortical bone of rabbits (7 wks and 12 wks). SEM, scanning Auger electron spectroscopy and atomic force microscopy revealed no differences in surface composition but marked differences in oxide thickness, surface topography and roughness. Light microscopic morphology and morphometry showed that all implants were in contact with bone, and had a large proportion of bone within the threads. The smooth, electropolished implants were surrounded by less bone than the machined implants with similar oxide thickness, (4-5 nm) and the anodically oxidized implants with thicker oxides (21 nm and 180 nm, respectively) after 7 wks. These studies show that a high degree of bone contact and bone formation can be achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, it appears that a reduction of surface roughness may influence the rate of bone formation in rabbit cortical bone.

Animals↗
PubMed1994

Molecular characterization of a recurring complex chromosomal translocation in two human extragonadal germ cell tumors.

The molecular characterization of a recurring complex chromosomal translocation involving 6p21, 6p22, 6q23, and 11q13 in two independent but similar extragonadal human germ cell tumors was initiated using fluorescence in situ hybridization (FISH) and pulse field gel electrophoresis (PFGE) techniques. By using a series of specific probes from the 11q13 region, the translocation breakpoint in this chromosomal band could be located within a long-range restriction enzyme map in between the markers D11S457 and D11S546. In addition, aberrantly hybridizing restriction fragments were revealed by PFGE in both tumors, indicating that the breakpoint region must be located within a distance of at maximum 200 kilobase pairs (kbp) from the nearest DNA marker (D11S546).

Blotting, Southern↗
PubMed1994

Somatic and MEN 2A de novo mutations identified in the RET proto-oncogene by screening of sporadic MTC:s.

Since germline mutations in the RET proto-oncogene (RET) predisposing to tumor development in Familial Medullary Thyroid Carcinoma (FMTC), Multiple endocrine neoplasia type 2A (MEN 2A), and Multiple endocrine neoplasia type 2B (MEN 2B) were reported, it has become possible to identify gene carriers with a very high degree of accuracy. Mutations in FMTC and MEN 2A exclusively affect cysteine residues in exon 10 and 11 of RET, whereas in MEN 2B codon 918 in exon 16 is involved. This latter mutation has also been described in a subset of apparently sporadic medullary thyroid carcinomas (MTC). Mutations in MEN 2B often occur as de novo germline mutations, whereas de novo mutations have not yet been described in FMTC or MEN 2A. We analyzed ten MTC:s and ten pheochromocytomas, all clinically judged to be sporadically occurring, by direct DNA sequencing of exons 10, 11, and 16 of RET. This analysis revealed a de novo germline mutation of codon 634 in exon 11 in a patient with MTC. In addition, somatic mutations of codon 918 in exon 16 in six of the remaining MTC:s were found. Interestingly, the presence of this somatic mutation was associated with a significantly less favorable clinical outcome.

Adult↗