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Biomedical subjects

L Philipson

Publications and source records attributed to L Philipson.

At least 73 records · Page 4Linked to original sources
PubMed1988

Evaluation of motor blockade by isometric force measurement and electromyographic recording during epidural anaesthesia--a methodological study.

Methods for assessing motor blockade by means of isometric force measurements and surface electromyographic (EMG) recordings in the lower extremities and abdominal wall were evaluated in 30 volunteers. The coefficients of variation were 10% for force measurements and 14% and 20% for average rectified EMG (RIEMG) recordings over the quadriceps muscle and abdominal muscles, respectively, and 8% overall for TURNS (the number of changes in the sign of the direction of the EMG signal). Seven of the 30 volunteers received epidural anaesthesia with 20 ml of mepivacaine 2% with adrenaline. The mean maximal cephalad analgesic level was T9. At that abdominal segment, RIEMG showed a reduction of 50% and TURNS of 20%. Isometric force and RIEMG recorded simultaneously in the quadriceps muscles during epidural anaesthesia displayed a linear relationship with a correlation coefficient of 0.91. TURNS was insensitive to force variations above 60% of maximum voluntary contraction. During the regression phase, 90% of both the initial force and RIEMG value was noted 180 min after the epidural injection. It is concluded that recording of RIEMG is a good method for quantitative assessment of motor blockade during epidural anaesthesia.

Abdominal Muscles↗
PubMed1988

The 89,000-Mr murine cytomegalovirus immediate-early protein stimulates c-fos expression and cellular DNA synthesis.

The immediate-early (IE) genes of murine cytomegalovirus (MCMV) are expressed in the absence of prior viral protein synthesis and regulate the transcription of MCMV early genes. The effect of MCMV IE genes on growth induction was studied. Different plasmids containing MCMV IE genes were microinjected into arrested NIH 3T3 mouse fibroblasts. Plasmids containing the ieI gene coding for the 89,000-Mr major IE protein pp89 were found to stimulate the expression of the c-fos protooncogene. Synthesis of pp89 and its transport to the nucleus appeared to be required for c-fos expression. DNA synthesis occurred in cells that were injected with MCMV IE genes and in neighboring cells that were not injected. The results suggest that the phosphoprotein pp89 stimulates cells to enter the cell cycle.

Animals↗
PubMed1987

Properties of a U1 RNA enhancer-like sequence.

The properties of a X.laevis U1B snRNA gene enhancer have been studied by microinjection in Xenopus oocytes. The enhancer-like sequence, defined as a short DNA stretch that is able to activate transcription in an orientation independent manner, is interchangeable between different U snRNA genes. The enhancer sequence alone does not, however, efficiently activate transcription from an SV40 pol II promoter but regains its activity when combined with the U-gene specific proximal sequence element. DNase I protection experiments show that the X.laevis U1B enhancer can interact specifically with a nuclear factor present in mammalian cells.

Animals↗
PubMed1987

A gene fusion system for generating antibodies against short peptides.

A novel method to obtain specific antibodies against short peptides is described, involving synthesis of the corresponding oligodeoxynucleotides followed by cloning into a new set of fusion vectors, pEZZ8 and pEZZ18, based on two synthetic IgG-binding domains (ZZ) of Staphylococcus aureus protein A. The soluble gene fusion product thus obtained, can be collected from the culture medium of Escherichia coli and rapidly recovered in a one-step procedure by IgG affinity chromatography. The system was used to express a fusion protein consisting of the two Z fragments and the C-terminal part [amino acids (aa) 57-70] of human insulin-like growth factor I (IGF-I). This 16-kDa protein was purified by affinity chromatography on IgG Sepharose and antibodies were raised in rabbits. The fusion protein elicited peptide-specific antibodies, as measured by solid-phase radioimmuno assay and Western blotting, reactive with both synthetic C-terminal peptide and the native human IGF-I protein. The results suggests that the gene fusion system can be used for efficient antibody production against short peptides encoded by synthetic oligodeoxynucleotides.

Amino Acid Sequence↗
PubMed1986

Cloning of the human cDNA for the U1 RNA-associated 70K protein.

Anti-RNP sera were used to isolate a cDNA clone for the largest polypeptide of the U1 snRNP, a protein of mol. wt 70 kd designated 70K, from a human liver cDNA library constructed in the expression vector pEX1. The cro-beta-galactosidase-70K fusion protein reacted with various anti-RNP patient sera, a rabbit anti-70K antiserum, as well as with a monoclonal antibody specific for this protein. The sequences of four 70K peptides were determined and they match parts of the deduced amino acid sequence of the 1.3 kb insert of p70.1 indicating that it is a genuine 70K cDNA. Screening of a new cDNA library constructed from polysomal mRNA of HeLa cells with the p70.1 clone yielded an overlapping clone, FL70K, which was 2.7 kb long and covered the complete coding and 3'-untranslated sequence of the 70K protein in addition to 680 nucleotides upstream of the putative initiation codon, The predicted mol. wt of the encoded protein is approximately 70 kd. Amino acid analysis of the purified HeLa 70K protein yielded values close or identical to those deduced from the nucleotide sequence of the full-length cDNA. The 70K protein is rich in arginine (20%) and acidic amino acids (18%). Extremely hydrophilic regions containing mixed-charge amino acid clusters have been identified at the carboxyl-terminal half of the protein, which may function in RNA binding. A sequence comparison with two recently cloned RNA binding proteins revealed homology with one region in the U1 RNP 70K protein. This domain may also be responsible for RNA binding.

Amino Acid Sequence↗
PubMed1986

Novel prolactin related mRNAs in rat pituitary cells.

From cytoplasm of rat pituitary GH4C1 tumour cells, anti prolactin anti-serum precipitates a polypeptide with apparent molecular weight of 75.000 in addition to prolactin. In vitro translation of size fractionated RNA shows that a 82.000 molecular weight PRL-like polypeptide is encoded by a mRNA larger than the 1 kb prolactin mRNA. Northern blot analysis shows that a rat prolactin cDNA probe hybridize to a 3.2 kb RNA and a 1.5 kb RNA in addition to the 1 kb PRL mRNA. The 82.000 molecular weight translation product and the 3.2 kb mRNA is also detected in rat anterior pituitary cytoplasm. We conclude that at least one high molecular weight mRNA which code for a prolactin-like polypeptide, is present in normal rat anterior pituitary gland and in GH4C1 cells.

Animals↗
PubMed1986

Production of specific antibodies against protein A fusion proteins.

The gene for Staphylococcal protein A was fused to the coding sequence of bacterial beta-galactosidase, alkaline phosphatase and human insulin-like growth factor I (IGF-I). The fusion proteins, expressed in bacteria, were purified by affinity chromatography on IgG-Sepharose and antibodies were raised in rabbits. All three fusion proteins elicited specific antibodies against both the inserted protein sequences and the protein A moiety. In the case of IGF-I, the protein A moiety in the fusion protein may act as an adjuvant since native IGF-I alone is a poor immunogen. The results suggest that the protein A fusion system can be used for efficient antibody production against peptides or proteins expressed from cloned or synthetic genes. To facilitate such gene fusions a set of optimized vectors have been constructed.

Alkaline Phosphatase↗
PubMed1986

Formation of the 3' end on U snRNAs requires at least three sequence elements.

The structural requirements for 3' end formation on the Xenopus laevis U1B snRNA gene have been studied. Three sequence elements are shown to be required. The first is a conserved sequence element found immediately 3' of all vertebrate U snRNA genes studied so far. The second is a gene internal sequence potentially capable of forming a stem-loop structure close to the 3' end of the RNA. The third element lies upstream of these, and may be part of the gene promoter. Experiments designed to investigate the mechanism of 3' end formation on primary U1B snRNA transcripts failed to find evidence for a processing event.

Acetyltransferases↗
PubMed1986

Primary structural relationships may reflect similar DNA replication strategies.

The primary structures of several proteins of bacterial and viral origin involved in the initiation of DNA synthesis and its subsequent elongation were compared. It was found that the known sequences of DNA polymerases and the single-stranded DNA binding proteins from phage T7 and Escherichia coli aligned well. Furthermore, segmental homologies were found in the phage phi 29 and adenovirus polymerases as well as in their DNA binding proteins. These results suggest similar mechanisms of DNA synthesis for E. coli and T7 on the one hand and for phi 29 and adenovirus on the other.

Adenoviruses, Human↗
PubMed1985

Efficient secretion and purification of human insulin-like growth factor I with a gene fusion vector in Staphylococci.

A novel approach for production of small polypeptides, using a staphylococcal protein A vector, is described. This system is used to express, secrete and purify human insulin-like growth factor I (IGF-I). A fusion protein consisting of protein A and IGF-I is recovered in high yield by passing the culture medium through an IgG affinity column. Using site-specific mutagenesis an acid labile asp-pro cleavage site was introduced at the fusion point between the two proteins. The protein A "tail" can thereby be removed from the affinity purified fusion protein by chemical cleavage releasing biologically active IGF-I molecules.

Escherichia coli↗
PubMed1985

Transcription signals in embryonic Xenopus laevis U1 RNA genes.

A genomic clone of the most abundant U1 RNA genes from Xenopus laevis was isolated from erythrocyte DNA and sequenced. Two different U1 RNA genes, U1A and U1B, are encoded in an HindIII 1.5-kb fragment and both are expressed after microinjection in Xenopus oocytes. Deletions and site-directed mutagenesis of the clones revealed two promoter elements in the U1B gene; one, located 250-220 nucleotides upstream from the 5' terminus of mature U1 RNA, functions as an activator, yielding a 10-fold promotion of transcription; the other, located 60-50 nucleotides upstream of the cap site, functions as an essential element for promotion of transcription. The U1A gene contained only the latter element in the cloned fragment. Homologous sequences can be identified in several U RNA genes of X. laevis.

Animals↗
PubMed1985

The release of growth arrest by microinjection of adenovirus E1A DNA.

The induction of DNA synthesis in growth-arrested mouse fibroblasts (NIH 3T3) was studied by microinjection of different constructs of adenovirus DNA using SV40 DNA and plasmid DNA as positive and negative controls. The E1A region of adenovirus types 2 and 12 appears to be sufficient to induce cellular DNA synthesis after growth arrest in approximately 30% of the cells and both 13S and 12S cDNA constructs mediate this effect. The presence of the E1A protein products as assayed by immunofluorescence does not strictly correlate with the induction of DNA synthesis in microinjected cells in contrast to the SV40 large T-antigen. Microinjection of truncated fragments of the Ad12 E1A region suggests, however, that the protein products of 12S and 13S may be involved in the induction process. A sequence comparison of the SV40 T-antigen and the adenovirus E1A products identified a region of significant homology providing a basis for a hypothesis concerning the evolution of T-antigen genes in DNA viruses.

Adenoviruses, Human↗