Search PubMed⌕ Search

Biomedical subjects

L Philipson

Publications and source records attributed to L Philipson.

At least 127 records · Page 7Linked to original sources
PubMed1981

Structure and restriction enzyme maps of the circularly permuted DNA of staphylococcal bacteriophage phi 11.

One restriction enzyme map of Staphylococcus aureus bacteriophage phi 11 DNA was established by reciprocal double digestions with the enzymes EcoRI, HaeII, and KpnI. The sequential order of the EcoRI fragments was thereafter established by a novel approach involving blotting of DNA partially cleaved with EcoRI and the probing the blots with nick-translated terminal fragments. A circular map of the phi 11 DNA was established, and the phage genome was circularly permuted based on the failure to end label mature viral DNA, restriction maps of replicating DNA, and finally, homoduplex analysis in the electron microscope. A restriction enzyme map of the prophage form of phi 11 DNA was obtained by analysis of chromosomal DNA from a lysogenic strain.

Chromosome Mapping↗
PubMed1981

Cloning of restriction fragments of DNA from staphylococcal bacteriophage phi 11.

EcoRI fragments of Staphylococcus aureus bacteriophage phi 11 DNA were cloned in vector plasmid pSA2100 in S. aureus. The clones were analyzed in marker rescue experiments with suppressor- and temperature-sensitive mutants of phi 11 to correlate the genetic and physical map. Several mutants could be identified on the physical map, and a clone containing fragment EcoRI-B of phi 11 DNA expressed immunity to phage infection. In addition, it was found that recombinant plasmids containing phi 11 DNA sequences can be transferred by high-frequency transduction after phage phi 11 infection of host cells.

Chromosome Mapping↗
PubMed1981

Control of adenovirus early gene expression: accumulation of viral mRNA after infection of transformed cells.

We studied the accumulation of viral mRNA in the presence of inhibitors of protein synthesis in an adenovirus type 5-transformed cell line (line 293 cells). An analysis of the endogenous viral mRNA's and proteins revealed that only early regions 1A and 1B were expressed in uninfected 293 cells. However, viral mRNA's from early regions 2, 3, and 4, as well as mRNA's from early regions 1A and 1B, accumulated in 293 cells after infection with adenovirus type 2. Cells treated with anisomycin before infection showed a drastic enhancement of mRNA from early region 4 compared with drug-free controls, This increase in viral mRNA was detected by using filter hybridization, S1 endonuclease mapping, and in vitro translation. The rate of transcription of early region 4 nuclear RNA also increased significantly in the presence of anisomycin. In contrast to the results with early region 4, the levels of cytoplasmic mRNA's from early regions 2 and 3 did not increase in cells treated with inhibitors. These results suggested that multiple virus encoded controls operate on the early regions of the adenovirus genome.

Adenoviruses, Human↗
PubMed1981

Control of adenovirus early gene expression: posttranscriptional control mediated by both viral and cellular gene products.

An adenovirus type 5 host range mutant (hr-1) located in region E1A and phenotypically defective in expressing viral messenger ribonucleic acid (RNA) from other early regions (Berk et al., Cell 17:935-944, 1979) was analyzed for accumulation of viral RNA in the presence of protein synthesis inhibitors. Nuclear RNA was transcribed from all early regions at the same rate, regardless of whether the drug was present or absent. As expected, low or undetectable levels of RNA were found in the cytoplasm of hr-1-infected cells compared with the wild-type adenovirus type 5 in the absence of drug. When anisomycin was added 30 min before hr-1 infection, cytoplasmic RNA was abundant from early regions E3 and E4 when assayed by filter hybridization. In accordance, early regions E3 and E4 viral messenger RNA species were detected by the S1 endonuclease mapping technique only in hr-1-infected cells that were treated with the drug. Similar results were obtained by in vitro translation studies. Together, these results suggest that this adenovirus type 5 mutant lacks a viral gene product necessary for accumulation of viral messenger RNA, but not for transcription. It is proposed that a cellular gene product serves as a negative regulator of viral messenger RNA accumulation at the posttranscriptional level.

Adenoviridae↗
PubMed1981

Myoelectric elbow and hand prosthesis controlled by signals from 2 muscles only, in a 9 year old girl.

A nine year old girl with a congenital above-elbow amputation was supplied with a myoelectrically controlled arm prosthesis at the Regional Hospital, Orebro, Sweden, in May 1978. The prosthesis was equipped with an artificial hand as well as an elbow joint. The latter was designed at New York University, for switch control but adapted to myoelectric control in the Department of Clinical Neurophysiology at the Regional Hospital, Orebro. The electric signals from the biceps and triceps muscles were used for the control of hand closing and opening as well as elbow flexion and extension. Two different control methods have been applied and clinically tested. The first is a three-level method in which slight contraction of biceps/triceps gives closing/opening motions of the hand and a higher contraction level in these muscles gives flexion/extension of the elbow. The second is a contraction-rate detection method in which slow contraction of biceps/triceps gives closing/opening of the hand and faster contraction of these muscles gives flexion/extension of the elbow. Both methods have been tested on the patient in a laboratory set-up and in a clinical trial which is still going on. Small electronic control circuits have been designed and placed inside the socket of the prosthesis, which is completely self contained. From the different tests performed, the second control method seems to be the most suitable for the actual patient. She is using her prosthesis every day, continuously improving her controlling ability.

Arm↗
PubMed1981

Digital approaches to myoelectric state control of prostheses.

The design of a new three-state myoelectric control system is presented. This controller determines its operating state from the initial rate of increase of the myoelectric signal, and the concept is realized in great measure through digital logic techniques. Proportional control of both active states (same dynamic range) is a unique feature of the controller. A microcomputer was interfaced in a simple way with myoelectric potentials to simulate the three-state controller described and to simulate various other state-determined control methods (some multifunctional). This was found to be a valuable method of evaluating control schemes without building the actual devices.

Adult↗
PubMed1980

Normal sleep pattern analyzed statistically and studied by color "dormograms".

Polygraphic sleep recordings were made from 46 healthy adult volunteers during 159 nights and evaluated visually. Sleep stages for each 30 sec epoch were entered into a computer data base from which plots of individual nights, as well as color "dormograms" and/or statistical parameters for a set of nights, could be produced. The total mean dormogram in which all the nights were synchronized at sleep onset revealed a dominant sleep pattern, which was found to be very stable even for subgroups. Synchronizing at the beginning of the second REM period allowed the pattern for the last half of the nights to appear more clearly. A large number of different sleep parameters were calculated for each night and statistically analyzed. On the basis of these results a normal "mean" sleep pattern could be reconstructed and related to other studies of normal sleep patterns.

Adult↗
PubMed1980

Further characterization of the phosphate moiety of the adenovirus type 2 DNA-binding protein.

The adenovirus type 2 DNA-binding protein is phosphorylated. Alkaline phosphatase treatment removes phosphate groups resulting in a decrease in molecular weight from 72000 to 70000. The dephosphorylated protein binds to single-stranded and double-stranded DNA as well as the phosphorylated protein does. Controlled chymotrypsin treatment cleaves the DNA-binding protein into two subspecies of Mr about 45000 and 25000. The 45000-Mr polypeptide contains most of the methionine residues but no phosphate and binds to DNA. The 25000-Mr polypeptide contains all the phosphate groups and shows no binding to DNA. Isoelectric focusing gels show heterogeneity of the DNA-binding protein and 15 subspecies with different charges can be observed after partial dephosphorylation by alkaline phosphatase. After extensive dephosphorylation two or three basic species with a molecular weight around 70000 are observed. Quantitative immunoprecipitation from cells labeled to equilibrium with inorganic 32PO4 gives a molar ratio of phosphate to protein of 4--7 and direct chemical determination of the phosphate residues yields 4 mol Pi/mol protein. These results suggest that there exist subspecies of the protein moiety of the adenovirus DNA-binding protein. The DNA-binding protein isolated from infected cells after a short 'pulse' of [35S]methionine has a molecular weight which corresponds to that of the dephosphorylated protein. After a 'chase' period the molecular weight increases to 72000, but alkaline phosphatase treatment converts it to a species with the same molecular weight as the newly synthesized DNA-binding protein, indicating that the modification of the protein is due to phosphorylation.

Adenoviruses, Human↗
PubMed1980

Limited proteolysis and a reactive cysteine residue define accesible regions in the native conformation of the adenovirus hexon protein.

The sulfhydryl group of one cysteine residue in the adenovirus hexon protein is accessible to alkylation in the absence of denaturating agents. This residue was [14C]carboxymethylated and characterized in peptides after proteolytic treatments. It was identified in two different types of digest and corresponded to the cysteine residue most accessible to oxidation. It is located close to residue 670 in the tentative amino acid sequence of the entire polypeptide. Trypsin has a highly limited action on the native hexon protein. Only three peptide bonds are fully susceptible to cleavage. These were found to occur in the N-terminal third of the protein, and were characterized as cleavages close to positions 150, 180 and 320 in the tentative structure of the polypeptide. Trypsin therefore liberates four fragments in major yield, with approximate Mr of 3000, 15000, 17000 and 78000. The smallest fragment corresponds to a highly acidic region. A limited, but less restricted susceptibility of hexon to chymotryptic cleavage was also found, and four major sites were characterized. The cysteine labelling and the proteolytic treatments define accessible regions in the native conformation of hexon. Together with previously assigned residue distributions, they suggest the subdivision of the entire polypeptide chain into three approximately equal parts, with accessible sites in the border regions, as well as in the middle of at least the N-terminal third. One model compatible with all data is presented.

Adenoviruses, Human↗
PubMed1980

Synthesis and processing of Semliki Forest virus-specific nonstructural proteins in vivo and in vitro.

A large short-lived virus-specific nonstructural protein with an apparent molecular weight of about 250000 (nsp250) has been isolated from cells infected with the temperature-sensitive mutants ts-4 and ts-6 of the Semliki Forest virus. nsp250 contained all peptides characteristic of the two previously identified nonstructural precursor proteins, nsp155 and nsp135, as revealed by limited proteolysis with Staphylococcus aureus V8 protease. Thus nsp250 is probably the translational product of the 5' two-thirds of the 42-S RNA genome which codes for the virus-specific nonstructural proteins. A second viral nonstructural precursor protein, nsp220, was also characterized by peptide mapping. This protein contained all the peptides of nsp155, and several but not all of the peptides of nsp135. Some peptides were demonstrated which possibly are derived from ns60, the only nonstructural protein not yet isolated. Small amounts of proteins with identical mobility to nsp250 and nsp220 were synthesized at 38 degrees C in micrococcal-nuclease-treated rabbit reticulocyte lysate in response to virion 42-S RNA from the ts-6 mutant. The product of the wild-type 42-S RNA in vitro contained, in addition to nsp220 and nsp155, polypeptides which comigrated with ns86, ns72 and ns70, indicating processing of the translational product. The authenticity of nsp220, nsp155 and ns70 synthesized in vitro was confirmed by limited proteolysis with V8 protease.

Animals↗
PubMed1979

A DRB (5,6 dichloro-beta-D-ribofuranosylbenzimidazole)-resistant adenovirus mRNA.

5,6-Dichloro-beta-D ribofuranosyl benzimidazole (DRB) inhibits transcription from the major late adenovirus promoter, located on the r-strand at map position 16.3 on the viral genome. 100-500 nucleotides long RNA chains with capped 5'-termini are transcribed from this promoter in the presence of 70 muM DRB. Synthesis of the mRNA for polypeptide IX which is unspliced and maps on the r-strand between positions 9.7 and 10.9 appears, however, to be DRB-resistant although it is transcribed by polymerase II and capped. Translatable mRNA for polypeptide IX is synthesized in the presence of DRB while the mRNAs for the other viral structural proteins are not synthesized. This differential DRB-inhibition of polymerase II transcription suggests either that short mRNAs may escape inhibition or that unspliced mRNAs are insensitive to the drug.

Adenoviruses, Human↗
PubMed1979

Purification of RNA-DNA hybrids by exclusion chromatography.

A simple method for selection of RNA-DNA hybrids has been developed and applied to the purification of adenovirus-specific messenger RNA. Cytoplasmic RNA prepared from adenovirus type 2 (ad2)-infected HeLa cells or from an ad2-transformed rat cell line was hybridized in solution to the complementary strands of ad2 DNA. The hybridization mixture was subsequently fractionated by chromatography on a Sepharose 2B column. The intact probe DNA as well as the RNA-DNA hybrids are excluded from the gel matrix and elute with the void volume. Nonhybridized RNA, in contrast, is included into the gel matrix and elutes as a broad peak well separated from the excluded fractions. Fractions corresponding to the void volume, were collected and the RNA-DNA hybrids were denatured in 90% formamide. The selected RNA was separated from the DNA by affinity chromatography on poly(U)-Sepharose. Restriction endonuclease fragments of DNA with a large enough size to make them excluded from the agarose column were also used for hybridization. In these experiments hybridizations were carried out under conditions which would allow R-loop formation (Thomas, M., White, R.L., and Davis, R.W. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2294-2298) and the hybridized RNA was separated from unhybridized RNA by Sepharose chromatography. The validity of the method was demonstrated by programming an in vitro protein-synthesizing system with selected RNA.

Adenoviruses, Human↗
PubMed1979

Parental adenovirus DNA accumulates in nucleosome-like structures in infected cells.

Micrococcal-nuclease digestion of adenovirus 2(ad 2) infected HeLa cell nuclei early after infection has been used to investigate the nucleoprotein nature of parental viral DNA. Viral DNA is more susceptible to nuclease digestion than cellular DNA. The pattern of digestion products changes as digestion proceeds from an indistinct pattern 1 hour post infection(pi) to a nucleosome-like pattern at 6 hours pi. The major differences between viral and cellular nucleoprotein products were i) a subnucleosome fraction from viral DNA and ii) the repeat size of DNA in viral nucleosomes was 165 base pairs and in cellular nucleosomes, 195 base pairs. Up to 50% viral DNA in nuclei 6 hours pi seems to be in nucleosome-like structures. Such patterns are not seen on digestion of partially-uncoated virus or isolated cores.

Adenoviruses, Human↗