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Biomedical subjects

M Salminen

Publications and source records attributed to M Salminen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Subtyping of human immunodeficiency virus type 1 strains by using antibodies specific for the third variable domain (V3) of gp120: results may be affected by divergent V3 sequences.

Human immunodeficiency virus type 1 serotype C was found in 545 of 712 Ethiopian patients by peptide enzyme immunoassay. Serotyping failed in 146 samples due to the absence of V3 antibodies or multiple reactivities. In 6 of 34 samples, discordant results were obtained by serotyping and genotyping, possibly due to divergent V3 sequences.

Amino Acid Sequence↗
PubMed1997

A combination of MEF3 and NFI proteins activates transcription in a subset of fast-twitch muscles.

The human aldolase A pM promoter is active in fast-twitch muscles. To understand the role of the different transcription factors which bind to this promoter and determine which ones are responsible for its restricted pattern of expression, we analyzed several transgenic lines harboring different combinations of pM regulatory elements. We show that muscle-specific expression can be achieved without any binding sites for the myogenic factors MyoD and MEF2 and that a 64-bp fragment comprising a MEF3 motif and an NFI binding site is sufficient to drive reporter gene expression in some but, interestingly, not all fast-twitch muscles. A result related to this pattern of expression is that some isoforms of NFI proteins accumulate differentially in fast- and slow-twitch muscles and in distinct fast-twitch muscles. We propose that these isoforms of NFI proteins might provide a molecular basis for skeletal muscle diversity.

Animals↗
PubMed1997

An ultrasound device in the diagnosis of acute maxillary sinusitis.

This multicenter study comprised 161 consecutive and unselected patients with suspected acute maxillary sinusitis (AMS). Altogether 322 maxillary sinuses were examined radiologically and by untrasound device (US). Of these, 234 antra were punctured, aspirated and irrigated. The volume of secretion coming out by irrigation was evaluated. The results of US, x-ray and irrigation were compared. For US, the proportion of correct positive results was 82.7% when the secretion volume was heavy, 78.6% when the secretion volume was moderate and 84.3% when the secretion volume was slight. When US finding was compared with the puncture result, the US gave false positive results in 8% of the cases and false negative results in 18.5% of the cases. Out of 187 positive irrigation findings, radiographs revealed fluid retention in 99 cases (score 3-6) (53%). Similarly, 11 radiographs showed fluid retention in 47 cases of negative irrigation findings (23.4%). Statistical calculation shows that both US and radiology were equally reliable in diagnosing fluid retention and sinusitis, when the results are compared with the findings of the sinus puncture. US and radiology gave false positive findings almost equally (p > 0.05). On the other hand, when the volume of secretion was slight (< 1 ml), US gave a fluid echo finding more often than radiology showed fluid retention.

Acute Disease↗
PubMed1997

Possible occurrence of a genetic bottleneck in dengue serotype 2 viruses between the 1980 and 1987 epidemic seasons in Bangkok, Thailand.

Cocirculation of two genetic subtypes of dengue serotype 2 viruses was first observed in the 1980 epidemic season in Thailand. To further delineate the evolutionary history and the contribution of these subtypes to subsequent epidemics, we determined the envelope glycoprotein gene sequence of 20 dengue serotype 2 viruses isolated from infected patients during 1987 and compared them with those derived from earlier years. Subtype IIIa strains represented the majority (18 of 19) of dengue type 2 viruses derived from Bangkok metropolitan area, whereas all three strains from a province in the northeastern region belonged to subtype IIIb, indicating uneven local distribution of dengue subtypes within the same year. Three types of sequence variation were identified in both subtypes: substitutions that were unique to individual strains; substitutions that were shared among all subtype IIIa or IIIb viruses of both the 1980 and 1987 epidemics; and those that were shared only among all subtypes IIIa or IIlb viruses of the 1987 epidemic, but were absent from the corresponding subtypes of 1980. While the first and second types of substitution were indicative of the most recent random mutations and previous mutations that had been fixed in virus populations, respectively, the third type suggested possible occurrence of a genetic bottleneck and subsequent expansion of one or a limited number of subtype IIIa strains in Bangkok between 1980 and 1987. Immunoblot analysis of intracellular NS1 antigen with anti-NS1 monoclonal antibodies also revealed antigenic heterogeneity of the NS1 protein that correlated with the subdivision based on envelope protein variation.

Amino Acid Sequence↗
PubMed1996

HIV-1 D subtype viruses in Finland.

BACKGROUND: Human immunodeficiency virus (HIV)-1 strains are divided into seven genetic subtypes based on their gag sequences (A, B, C, D, F, G and H). Strains that have appeared in Finland show unusual heterogeneity compared to most industrialized countries, up to 25% of the strains belong to non-B subtypes (Liitsola et al., 1996). Three D subtype viruses have so far been identified in Finland. All patients were men, one Kenyan immigrant and two Finnish men, who had been infected in Africa. Here we describe some of the characteristics of the genomic diversity of these strains. METHOD: The genotype was determined by direct solid-phase sequencing of the p7 gag region. Phylogenetic analysis was done using standard methods. RESULTS: The analysis showed that the D subtype sequences clustered clearly distinctly from the other non-B strains, but did not suggest any transmission links between the three cases. From one case both cerebrospinal fluid (CSF) and blood leukocyte virus isolates were studied. The analysis revealed significant differences between the blood and CSF viruses. A four amino acid duplication and other differences were observed between the strains. CONCLUSION: The results confirm that D subtype viruses do indeed occur in Finland and they represent quite heterogenic strains within the D cluster.

Journal Article↗
PubMed1996

Fast-muscle-specific DNA-protein interactions occurring in vivo at the human aldolase A M promoter are necessary for correct promoter activity in transgenic mice.

The human aldolase A tissue-specific M promoter (pM) has served as a model system for identifying pathways that lead to fast-muscle-specialized expression. The current study has delimited the sequences necessary and sufficient for fast-muscle-specific expression in transgenic mice to a short 209-bp fragment extending from bp -164 to +45 relative to the pM transcription start site. Genomic footprinting methods showed that in this proximal region, the same elements that bind muscle nuclear proteins in vitro are involved in DNA-protein interactions in intact muscle nuclei of transgenic mice. Furthermore, these experiments provided the first evidence that different DNA-binding activities exist between slow and fast muscles in vivo. Fast-muscle-specific interactions occur at an element named M1 and at a muscle-specific DNase I-hypersensitive site that was previously detected by in vitro methods. The formation of the muscle-specific DNase I-hypersensitive site reflects binding of proteins to a close element, named M2, which contains a binding site for nuclear factors of the NF1 family. Mutational analysis performed with transgenic mice confirmed the importance of the M1 element for high-level fast-muscle-specific pM activity and suggested that the M2/NF1 element is differently required for correct pM expression in distinct fast muscles. In addition, two other protein binding sites, the MEF3 motif and the USF site, seem to act as stage-specific activators and/or as participants in the establishment of an active chromatin configuration at pM.

Animals↗
PubMed1996

Improvement of insulin action in diabetic transgenic mice selectively overexpressing GLUT4 in skeletal muscle.

To investigate the role of glucose transporter expression in whole-body glucose homeostasis, we have created transgenic mice that have a 2.0- to 3.5-fold increase in GLUT4 glucose transporter level in skeletal muscle and heart. This increase is sufficient to significantly improve insulin action and to reduce basal blood glucose levels in transgenic streptozotocin-induced diabetic mice. These results provide the first evidence of a direct causality between skeletal muscle GLUT4 transporter level and overall insulin responsiveness.

Adipose Tissue↗
PubMed1995

Myotube-specific activity of the human aldolase A M-promoter requires an overlapping binding site for NF1 and MEF2 factors in addition to a binding site (M1) for unknown proteins.

The human aldolase A gene is expressed in several tissues through the use of three alternative promoters. The activity of one of the promoters, pM, is restricted to skeletal muscle. We reported previously that a proximal 280 bp pM fragment confers tissue-specific expression to a CAT reporter gene in transgenic mice. This small regulatory region directs expression to muscle composed mainly of fast-twitch fibers. Here we show that a minimal promoter fragment from base-pairs -164 to +45 is sufficient to highly active pM during myoblast differentiation in cell culture and demonstrate that two DNA elements play a major role in this activation. These elements consist of a binding site (M1) for unknown ubiquitous proteins and an overlapping binding site for MEF2 and NF1 families of transcription factors. The NF1 factor constitute the main binding activity on the MEF2/NF1 site and, interestingly, some of the DNA-protein complexes that form with muscle nuclear extracts on the NF1 element differ from those that form with non-muscular extracts.

Animals↗
PubMed1994

Genomic organization of the human catechol O-methyltransferase gene and its expression from two distinct promoters.

Human genomic DNA fragments containing catechol O-methyltransferase (COMT) sequences were isolated and the exon-intron structure analysed by sequencing, PCR and comparing to the human COMT cDNA sequences. The gene contains six exons, of which exons 1 and 2 are noncoding. MB-ATG and S-ATG codons, responsible for the initiation of translation of the membrane-bound (MB) and soluble (S) forms of the enzyme, are located in exon 3. Two distinct COMT-specific transcripts, 1.3 kb and 1.5 kb, were detected in various human tissues and cell lines. Different quantities of the shorter COMT-specific mRNA in the tissues studied suggest a tissue-specific regulation of the COMT gene at transcriptional level. Mapping of the 5' ends of the COMT mRNAs showed that transcription initiates at multiple sites in two separate DNA regions, which are preceded by functional promoter sequences. The proximal promoter (P1), located between the two translation initiation codons and extending approximately 200 bp upstream of the MB-ATG initiation codon, apparently gives rise to the 1.3-kb S-COMT mRNA (S-mRNA). The distal promoter (P2) is located in a DNA fragment in front of and partly overlapping the transcription-start region of the 1.5-kb transcript, suggesting that it controls the expression of this MB-mRNA. Similarities between the rat and human COMT gene promoters are analyzed.

Animals↗
PubMed1994

Morphological differentiation of human SH-SY5Y neuroblastoma cells inhibits human immunodeficiency virus type 1 infection.

We have studied human immunodeficiency virus type 1 (HIV-1) infection in human SH-SY5Y neuroblastoma cells at various stages of morphological differentiation. Two days' treatment of the cells with retinoic acid (RA) or dibutyryl cAMP (db-cAMP) resulted in the appearance of elongated neurites and enhanced production of 160K to 200K neurofilament proteins as shown by indirect immunofluorescence. DNA synthesis was reduced only in RA-treated cells as detected by 5-bromo-2'-deoxyuridine incorporation. The cells were infected with two T-lymphotropic virus strains (IIIB and NDK) and two fresh isolates (39001 and 46001) from bronchoalveolar lavage samples of AIDS patients. The latter two isolates were unable to form syncytia in infected CD4-positive T-lymphoblastoid C8166 cells which was in contrast to our T-lymphotropic virus strains. Interphase in situ hybridization showed that 14 to 16% of SH-SY5Y cells become positive for HIV-1 DNA. Regardless of the virus strain, morphological differentiation of the cells with RA or db-cAMP inhibited infection by 50% at a single cell in situ resolution. Nested PCR confirmed the presence of proviral DNA in the infected cells. These results show that human neuroblastoma cells, tumour cells of neuroectodermal origin, can be infected by different HIV-1 isolates and that the infection is inhibited by neurotypic cell differentiation.

Base Sequence↗
PubMed1994

Fast-muscle-specific expression of human aldolase A transgenes.

The expression of the human aldolase A gene is controlled by three alternative promoters. In transgenic mice, pN and pH are active in all tissues whereas pM is activated specifically in adult muscles composed mainly of fast, glycolytic fibers. To detect potential regulatory regions involved in the fast-muscle-specific activation of pM, we analyzed DNase I hypersensitivity in a 4.3-kbp fragment from the 5' end of the human aldolase A gene. Five hypersensitive sites were located near the transcription initiation site of each promoter in those transgenic-mouse tissues in which the corresponding promoter was active. Only one muscle-specific hypersensitive site was detected, mapping near pM. To functionally delimit the elements required for muscle-specific activity of pM, we performed a deletion analysis of the aldolase A 5' region in transgenic mice. Our results show that a 280-bp fragment containing 235 bp of pM proximal upstream sequences together with the noncoding M exon is sufficient for tissue-specific expression of pM. When a putative MEF-2-binding site residing in this proximal pM region is mutated, pM is still active and no change in its tissue specificity is detected. Furthermore, we observed a modulation of pM activity by elements lying further upstream and downstream from pM. Interestingly, pM was expressed in a tissue-specific way in all transgenic mice in which the 280-bp region was present (32 lines and six founder animals). This observation led us to suggest that the proximal pM region contains elements that are able to override to some extent the effects of the surrounding chromatin.

Animals↗
PubMed1993

Molecular epidemiology of HIV-1 based on phylogenetic analysis of in vivo gag p7/p9 direct sequences.

Viruses of different geographical origin are circulating in Finland. We wanted to test whether phylogenetic analysis of patient lymphocyte proviral quasispecies sequences could be used to group different strains into genetic lineages. The gag p7/p9 coding region was analyzed using solid-phase direct sequencing from 30 patients in Finland and Estonia. Proviral sequences were found to represent at least four, possibly even five, different, highly diverged major lineages. Different methods of phylogenetic analysis resulted in the same conclusion. Serial samples from the same patients, taken over a period of several years showed limited variation over time. Cases of potential patient-to-patient transmission or common source of infection were identified based on the sequence analysis. Compared to similar analyses of longer genome segments, the gag p7/p9 nucleic acid binding protein coding region produces analogous results in phylogenetic analysis. The method can be used as a rapid way of determining the genetic subtype of HIV-1 strains circulating in populations.

Capsid Proteins↗
PubMed1993

HIV-infection in Estonia.

Only a few cases of clinical AIDS have been diagnosed in the Baltic countries that previously were part of the Soviet Union. This suggests that the spread of HIV-infection has been much slower than in several other countries belonging to the previous Eastern Europe. To get a more precise picture of the situation, we have analyzed the data from seroepidemiological screening programs that have been conducted in Estonia since June 1987. Large population groups were tested according to a decree by the former soviet All-Union center on AIDS. On several occasions the tests were mandatory and probably had a coverage close to 100%. After more than a million serum samples were tested, 29 HIV-infected persons, 3 women and 26 men have been identified. One of them was HIV-2 positive. Most of them live in Tallinn, the capital city of Estonia. All cases probably have a sexually transmitted infection. In one the infection has proceeded to clinical AIDS. Analysis of the gene sequences of several strains suggests that the strains are closely related and that the number of sources of infection is quite small. The study suggests that the spread of HIV in Estonia is still quite limited. A contributing factor may be the restricted possibilities for travel to the Western countries during the Soviet era.

Journal Article↗
PubMed1993

Structure of the rat catechol-O-methyltransferase gene: separate promoters are used to produce mRNAs for soluble and membrane-bound forms of the enzyme.

The enzyme catechol-O-methyltransferase (COMT) catalyzes the inactivation of catechol-containing molecules by methylation. The cDNAs for the rat and human COMT have recently been cloned and recombinant proteins expressed in prokaryotic and eukaryotic cells. We describe here the structure of the rat COMT gene and its 5'-flanking sequences. The gene spans at least 13 kb and is composed of 5 exons, the first one noncoding. The two ATG codons for the initiation of translation of the membrane-bound (MB-COMT) and soluble (S-COMT) forms of the enzyme reside in the second exon. The gene expresses two mRNA species of 1.6 kb and 1.9 kb that have different tissue distributions. The expression of the transcripts is regulated by at least two promoters, P1 and P2. The P1 promoter expresses the shorter transcript in a tissue-specific manner and is located between the ATG codons in the coding region of the longer transcript. The P2 promoter is constitutive and responsible for the expression of the longer transcript. The shorter 1.6-kb mRNA (S-mRNA) produces only the S-COMT polypeptide, whereas the longer 1.9-kb mRNA (MB-mRNA) is able to direct synthesis of both forms of the COMT enzyme.

Animals↗
PubMed1993

An opportunistic promoter sharing regulatory sequences with either a muscle-specific or a ubiquitous promoter in the human aldolase A gene.

The human aldolase A gene is transcribed from three different promoters, pN, pM, and pH, all of which are clustered within a small 1.6-kbp DNA domain. pM, which is highly specific to adult skeletal muscle, lies in between pN and pH, which are ubiquitous but particularly active in heart and skeletal muscle. A ubiquitous enhancer, located just upstream of pH start sites, is necessary for the activity of both pH and pN in transient transfection assays. Using transgenic mice, we studied the sequence controlling the muscle-specific promoter pM and the relations between the three promoters and the ubiquitous enhancer. A 4.3-kbp fragment containing the three promoters and the ubiquitous enhancer showed an expression pattern consistent with that known in humans. In addition, while pH was active in both fast and slow skeletal muscles, pM was active only in fast muscle. pM activity was unaltered by the deletion of a 1.8-kbp region containing the ubiquitous enhancer and the pH promoter, whereas pN remained active only in fast skeletal muscle. These findings suggest that in fast skeletal muscle, a tissue-specific enhancer was acting on both pN and pM, whereas in other tissues, the ubiquitous enhancer was necessary for pN activity. Finally, a 2.6-kbp region containing the ubiquitous enhancer and only the pH promoter was sufficient to bring about high-level expression of pH in cardiac and skeletal muscle. Thus, while pH and pM function independently of each other, pN, remarkably, shares regulatory elements with each of them, depending on the tissue. Importantly, expression of the transgenes was independent of the integration site, as originally described for transgenes containing the beta-globin locus control region.

Animals↗
PubMed1992

Rapid and simple characterization of in vivo HIV-1 sequences using solid-phase direct sequencing.

Solid-phase direct sequencing was used to obtain in vivo sequence data of polymerase chain reaction (PCR)-amplified HIV-1 p25/p7 gene segments. The solid-phase sequencing method was compared to double-strand sequencing of preparative gel electrophoresis-purified amplification products and found to give more consistent results. Lysates of cells were compared to purified DNA as PCR template. HIV-1 sequences were as well amplified from lysates as from purified DNA and 7,780 bp of sequence from 41 samples were produced by direct sequencing. Sequence analysis revealed common sequence motifs relating the sequence to the Euroamerican and African groups of sequences previously described. The results indicate that many viruses of diverse origin circulate in Finland, although the majority seems to be of Euroamerican type. Solid-phase direct sequencing may provide a valuable tool for both epidemiological and pathogenic studies of in vivo HIV-1 infections.

Amino Acid Sequence↗