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Biomedical subjects

A Kraszewski

Publications and source records attributed to A Kraszewski.

46 records · Page 3Linked to original sources
PubMed1978

Comparative effects of oestrogen and a progestogen on bone loss in postmenopausal women.

1. The value of progestogen therapy in the prevention of postmenopausal bone loss was assessed in 30 women, by a preliminary randomized controlled trial of gestronol or mestranol, in comparison with a placebo. 2. When the skeletal response was measured by photon absorptiometry, bone mineral loss was prevented by both the oestrogen and the progestogen. 3. We confirm that mestranol significantly reduced the urinary output of hydroxyproline-containing peptide, but this did not occur during gestronol therapy, suggesting that progestogen has a different action on bone, perhaps stimulating bone formation.

Adult↗
PubMed1978

Chemical synthesis of genes for human insulin.

A rapid chemical procedure has been developed and used for the synthesis of 29 oligodeoxyribonucleotides to build synthetic genes for human insulin. The gene for insulin B chain, 104 base pairs, and the one for A chain, 77 base pairs, were designed from the amino acid sequence of human polypeptides. They bear single-stranded cohesive termini for the EcoRI and BamHI restriction endonucleases and are designed to be inserted separately into a pBR322 plasmid. The synthetic fragments, deca- to pentadecanucleotides, were synthesized by a block phosphotriester method with trinucleotides as building blocks. Final purification was by high-performance liquid chromatography. All 29 oligonucleotides were pure and had the correct sequences.

DNA↗
PubMed1978

The chemical synthesis of the anticodon loop of an eukaryotic initiator tRNA containing the hypermodified nucleoside N6-/N-threonylcarbonyl/-adenosine/t6A/1.

In this work, the first example of chemical synthesis of oligoribonucleotide containing the hypermodified nucleoside N6-/N-threonylcarbonyl/-adenosine /t6A/ is presented. Synthesis of the heptamer C-C-C-A-U-t6A-A IX, the sequence of which is related to the anticodon loop of the initiator tRNA from yellow lupine, was achieved by: /i/ phosphotriester block synthesis of suitably protected heptamer VI containing an adenosine unit with a free exo-NH2 group, /ii/ highly effective "one-flask" procedure for the transformation of the free exo-NH2 group of adenosine unit of heptamer VI into a N,N'-disubstituted urea system of t6A of heptamer VII /hypermodification/, and /iii/ final deprotection of VIII /32% total yield/ with the use of a new approach for simultaneous hydrogenolysis /PdO-hydrogen-pyridine/ of the p-nitrobenzyl group and 2,2,2-trichloroethyl groups from carboxyl function of t6A and internucleotide phosphates respectively.

Adenosine↗
PubMed1977

Nucleoside 3'-phosphotriesters as key intermediates for the oligoribonucleotide synthesis. IV. New method for removal of 2,2,2-trichloroethyl group and 31P NMR as a new tool for analysis of deblocking of internucleotide phosphate protecting groups.

Zinc/acetylacetone/pyridine treatment has been designed as a very efficient method for removal of 2,2,2,-trichloroethyl group from phosphoesters. Internucleotide and terminal 2,2,2-trichloroethylphosphotriesters were transformed to corresponding diesters quantitatively. Much less reactive 2,2,2-trichloroethylphosphodiesters produced monoesters with ca. 90% yield. 31P NMR spectroscopy has been proposed as a new tool for analysis of removal of internucleotide phosphate protecting groups-a crucial step in oligonucleotides synthesis via phosphotriester approach.

Chromatography, Thin Layer↗
PubMed1976

Nucleoside-3'-phosphotriesters as key intermediates for the oligoribonucleotide synthesis. III. An improved preparation of nucleoside 3'-phosphotriesters, their 1H NMR characterization and new conditions for removal of 2-cyanoethyl group.

An improved procedure for the transformation of 5'-O-monomethoxytrityl-2'-O-acetyl-3'-phosphates of uridine la, inosine ib and 6-N-benzoyladenosine lc into corresponding 3'/2,2,2-trichloroethyl, 2-cyanoethyl/-phosphates iiaic is reported. H NMR characterization of nucleoside 3'-phosphotriesters is presented. New conditions i.e. anhydrous triethylamine-pyridine treatment have been found for the selective removal of 2-cyanoethyl group from nucleoside 3'-phosphotriesters in the presence of neighbouring 2'-O-acetyl one.

Adenosine↗
PubMed1971

Intestinal spirochaetosis.

An abnormal condition of the large intestine is described in which the surface epithelium is infested by short spirochaetes. Diagnosis can be made by light microscopy. A review of 14 cases diagnosed by rectal biopsy and 62 cases involving the appendix shows no consistent symptom complex. The possible significance is discussed.

Adult↗
PubMedDate not supplied

Studies on reactions of nucleoside H-phosphonates with bifunctional reagents. Part VI. Reaction with diols.

Reactions of nucleoside H-phosphonates with various diols using different types of condensing agents have been studied. Depending on the coupling procedure and the length of a polymethylene chain of the diol, acyclic H-phosphonate diesters or cyclic phosphite triesters were formed. The course of oxidation with iodine to produce cyclic nucleoside alkyl phosphotriesters or hydroxyalkyl nucleoside phosphodiesters can be controlled by the amount of water present in the reaction medium.

Indicators and Reagents↗