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Biomedical subjects

M Petersen

Publications and source records attributed to M Petersen.

138 records · Page 8Linked to original sources
PubMedDate not supplied

The conformations of locked nucleic acids (LNA).

We have used 2D NMR spectroscopy to study the sugar conformations of oligonucleotides containing a conformationally restricted nucleotide (LNA) with a 2'-O, 4'-C-methylene bridge. We have investigated a modified 9-mer single stranded oligonucleotide as well as three 9- and 10-mer modified oligonucleotides hybridized to unmodified DNA. The single-stranded LNA contained three modifications whereas the duplexes contained one, three and four modifications, respectively. The LNA:DNA duplexes have normal Watson-Crick base-pairing with all the nucleotides in anti-conformation. By use of selective DQF-COSY spectra we determined the ratio between the N-type (C3'-endo) and S-type (C2'-endo) sugar conformations of the nucleotides. In contrast to the corresponding single-stranded DNA (ssDNA), we found that the sugar conformations of the single-stranded LNA oligonucleotide (ssLNA) cannot be described by a major S-type conformer of all the nucleotides. The nucleotides flanking an LNA nucleotide have sugar conformations with a significant population of the N-type conformer. Similarly, the sugar conformations of the nucleotides in the LNA:DNA duplexes flanking a modification were also shown to have significant contributions from the N-type conformation. In all cases, the sugar conformations of the nucleotides in the complementary DNA strand in the duplex remain in the S-type conformation. We found that the locked conformation of the LNA nucleotides both in ssLNA and in the duplexes organize the phosphate backbone in such a way as to introduce higher population of the N-type conformation. These conformational changes are associated with an improved stacking of the nucleobases. Based on the results reported herein, we propose that the exceptional stability of the LNA modified duplexes is caused by a quenching of concerted local backbone motions (preorganization) by the LNA nucleotides in ssLNA so as to decrease the entropy loss on duplex formation combined with a more efficient stacking of the nucleobases.

Carbohydrates↗
PubMedDate not supplied

Modulation of calcium-currents by capsaicin in a subpopulation of sensory neurones of guinea pig.

The action of capsaicin (CAP) on the total Ca2+ current was examined in internally perfused voltage-clamped dorsal root ganglion (DRG) neurones of guinea pigs. CAP changed the total Ca2+ current in about 50% of the investigated DRG neurones ("CAP-sensitive" neurones) in the following way: (I) a transient increase of the current amplitude at potentials between -35 mV and about -10 mV was accompanied by a shift of the current-voltage relation towards negative potentials by 5-8 mV; (II) the current inactivation was accelerated at potentials positive to about -35 mV; and (III) the current activation of Ca2+ currents (time to peak values) was also accelerated. Separated low voltage-activated (T-type) currents at potentials negative to about -35 mV were either not affected or reduced. It remains undecided whether CAP increases T-type currents in a particular potential range or activates an N-type current. External application of 50 microM Ni2+ blocks the effect of CAP, but does not affect the acceleration of the high voltage-activated (L-type) current inactivation induced by menthol. This appears to exclude a CAP effect on L-type current inactivation. "CAP sensitive" and "CAP insensitive" neurones could be discriminated by their different Ca2+ currents: the former demonstrate both fast and slow inactivating currents while the latter have only L-type currents. The observed changes of fast-inactivating Ca2+ currents may be related to the specific action of CAP on peptidergic sensory neurones.

Animals↗
PubMedDate not supplied

In vivo cytogenetic studies on mice exposed to ethylene dibromide.

The pesticide, ethylene dibromide (EDB), was evaluated with in vivo cytogenetic assays to determine its genotoxicity. CD1 male mice were exposed to EDB through intraperitoneal injections. Bone marrow cells isolated from femora were analyzed for sister-chromatid exchange (SCE), chromosome aberration and micronucleus formation. The results showed that only certain concentrations of EDB tested caused a slight but significant increase in SCEs and chromosome aberrations. However, these increases were not dose-related. No increase in the polychromatic erythrocytes with micronuclei was observed following EDB exposure. Also, EDB did not cause cell-cycle delay in comparison with controls. Thus, it appears that EDB is not an effective genotoxic agent in vivo in mice.

Animals↗
PubMedDate not supplied

Prolonged neuromuscular blockade following vecuronium infusion.

Administration of vecuronium by infusion is an increasingly common technique, both in the operating room and in the intensive care unit (ICU), for patients requiring prolonged neuromuscular blockade and mechanical ventilation. The major advantage of vecuronium over older neuromuscular blocking agents is its rapid excretion and intermediate duration of action. Prior to the current case report, the longest reported continuous paralysis after the cessation of a vecuronium infusion was 90 hours. A case of an 81-year-old patient with renal failure and subclinical chronic cirrhosis of the liver, who remained paralyzed for 13 days following a vecuronium infusion, is described. Intensive monitoring of neuromuscular function is recommended whenever muscle relaxants are administered by continuous infusion.

Aged↗
PubMedDate not supplied

Solution structure of a DNA complex with the fluorescent bis-intercalator TOTO modified on the benzothiazole ring.

We have used two-dimensional 1H NMR spectroscopy to determine the solution structure of the DNA oligonucleotide d(5'-CGCTAGCG-3')2 complexed with the bis-intercalating dye 1,1'-(4,4,8,8-tetramethyl-4, 8-diazaundecamethylene)bis-4-[3-ethyl-2,3-dihydro(benzo-1, 3-thiazolyl)-2-methylidene]quinolinium tetraiodide (TOTOEt). The determination of the structure was based on a total relaxation matrix analysis of the NOESY cross-peak intensities. DQF-COSY spectra were used to obtain coupling constants for the deoxyribose ring protons. The coupling constants were transformed into angle estimates. The NOE-derived distance and dihedral restraints were applied in restrained molecular dynamics calculations. Twenty final structures each were generated for the TOTOEt complex from both A-form and B-form double-stranded (ds) DNA starting structures, giving a total of 40 final structures. Since many NOE contacts were observed between TOTOEt and dsDNA, the resulting structure has a fairly high resolution and allows determination of local features in the dsDNA structure after TOTOEt binding. The root-mean-square (rms) deviation of the coordinates for the 40 structures of the complex was 0.52 A. The local DNA structure is distorted in the complex. The helix is unwound by 80 degrees and has an overall helical repeat of 12 base pairs, caused by bis-intercalation of TOTOEt. The benzothiazole ring system is twisted relative to the quinoline in the uncomplexed TOTOEt molecule. The site selectivity of TOTOEt for the CTAG.CTAG site is explained by its ability to adapt to the base pair propeller twist of dsDNA to optimize stacking and the hydrophobic interaction between the thymidine methyl group and the benzothiazole ring. The polypropylene amine linker chain is located in the minor groove of dsDNA. The N-ethyl group on the benzothiazole of TOTOEt is placed in the major groove pointing toward the center of the oligonucleotide and the dyad symmetry axis of the complex. This orientation seems to make it feasible to create a TOTO analogue with a linker connecting the two chromophores in the major groove. The design of such an analogue and a macrocyclic analogue with a linker in both the major groove and the minor groove seems to be straightforward.

DNA↗
PubMedDate not supplied

Bis-intercalation of homodimeric thiazole orange dye derivatives in DNA.

The thiazole orange dye 1,1'-(4,4,8,8-tetramethyl-4, 8-diazaundecamethylene)-bis-4-[(3-methyl-2,3-dihydro-2(3H)-benzo-1 ,3-thiazolylidene)methyl]quinolinium tetraiodide (TOTO) binds to double-stranded DNA (dsDNA) in a sequence selective bis-intercalation. We have examined the binding of derivatives of TOTO with different substituents on the benzothiazole ring. The analogues are the following: 1,1'-(4,4,8,8-tetramethyl-4, 8-diazaundecamethylene)-[4-[3-(benzyl-2, 3-dihydro-2-(3H)-benzothiazolylidene)methyl]quinolinium]-[4-[3-(++ +methy l-2, 3-dihydro-2-(3H)-benzothiazolylidene)methyl]quinolinium]tetraio dide (TOTOBzl) and 1,1'-(4,4,8,8-tetramethyl-4, 8-diazaundecamethylene)-bis-4-[(3-ethyl-2,3-dihydro-2(3H)-benzo-1, 3-thiazole)methyl]quinolinium tetraiodide (TOTOEt). In this paper, we report the synthesis of TOTOBzl and TOTOEt together with the one- and two-dimensional 1H NMR investigations of complexes between these TOTO analogues and the dsDNA oligonucleotide d(CGCTAGCG)2. Both analogues yield extremely stable complexes in which each chromophore is sandwiched between two base pairs in a (5'-CpT-3'):(5'-ApG-3') site. The linker spans over two base pairs in the minor groove. The benzyl group in TOTOBzl and the ethyl groups in TOTOEt is pointing outward in the major groove.

Benzothiazoles↗
PubMedDate not supplied

Presence of stable coal radicals in autopsied coal miners' lungs and its possible correlation to coal workers' pneumoconiosis.

Stable coal radicals (SCRs) were detected by electron spin resonance (ESR) spectroscopy in the lung tissue of autopsied coal miners. The SCR concentrations were measured in the lung tissues from 98 coal miners with and without (a) coal workers' pneumoconiosis (CWP), (b) cancer, and (c) a history of cigarette smoking. Concentrations of SCRs were also determined in the lungs of nonminer controls. The SCR concentration was related to longer mining tenure, CWP disease severity, lung cancer, and cigarette smoking. The mean concentration of SCRs in the lung tissues of miners with 30 +/- 1.4 y of coal mining exposure was 5.3 +/- 1.3 x 10(17) spins/g versus controls who had a nondetectable level (less than 10(15) spins/g). An increase in disease severity was accompanied by a progressive increase in SCR concentration. A SCR concentration of 4.8 +/- 0.7 x 10(17) spins/g was found for simple CWP (with moderate coal macules) versus 7.8 +/- 4.6 spins/g lung tissue for complicated CWP (with progressive massive fibrosis). Significantly higher (i.e., 10 x 10(17] concentrations of SCR in the coal miners' lung tissues were associated with an exposure history in the anthracite regions of northeastern Pennsylvania. These results indicate a possible role for SCRs in the disease process. Furthermore, ESR appears to be an adequate methodology for the quantitation of coal dust retained in the lung and for distinguishing exposures to anthracite and/or bituminous coal.

Aged↗
PubMedDate not supplied

LNA (locked nucleic acid) and the diastereoisomeric alpha-L-LNA: conformational tuning and high-affinity recognition of DNA/RNA targets.

The remarkable binding properties of LNA (Locked Nucleic Acid) and alpha-L-LNA (the alpha-L-ribo configured diastereoisomer of LNA) are summarized, and hybridization results for LNA/2'-O-Me-RNA chimera and LNAs with a "dangling" nucleotide are introduced. In addition, results from NMR investigations on the furanose conformations of the individual nucleotide monomers in different duplexes are presented. All these data are discussed with focus on the importance of conformational steering of unmodified nucleotides in partly modified LNA and alpha-L-LNA sequences in relation to the unprecedented binding properties of LNA and alpha-L-LNA.

DNA↗
PubMedDate not supplied

Synthesis and NMR-analysis of tricyclic nucleosides.

Two anomeric tricyclic nucleosides have been synthesised from diacetone-D-glucose using oxidation, stereoselective Grignard-addition of a vinyl-group, a stereoselective dihydroxylation followed by a tandem ring closing reaction, and finally a nucleobase coupling. The main beta-configured product was examined and its configuration confirmed using NMR-spectroscopy in connection to ab initio calculations. The preferred conformation of this tricyclic nucleoside was described.

Hydrocarbons, Cyclic↗
PubMedDate not supplied

What are blood counts? A computer-assisted program for pediatric patients.

The diagnosis of cancer in a child leaves the parents and child faced with a life-threatening illness in addition to the need to learn about how the illness will impact their lives. Education about the disease process, treatment regimen, and possible side effects of therapy must occur. The educational process, often consisting of didactic teaching sessions, often does not lend itself well to the individual learning needs of the child. A more individualized and developmentally appropriate method of educating children was developed, consisting of the development of a computer-assisted instructional (CAI) program on blood counts.

Adolescent↗