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Biomedical subjects

K Nath

Publications and source records attributed to K Nath.

At least 55 records · Page 3Linked to original sources
PubMed1981

Cleavage properties of site-specific restriction endonucleases.

Among the various restriction sites present on a DNA molecule, the restriction endonucleases prefer specific ones. This site preference may be an inherent property of the restriction endonucleases or may reflect the complexities inherent in the DNA molecule. The site preference of restriction endonucleases can be amplified by the use of intercalators that bind to DNA. This can lead to the production of large and partially cleaved DNA fragments. General protein inhibitors that react with sulfhydryl groups can affect the activities of some restriction endonucleases. This can result in the formation of partially digested DNA fragments. Another approach leading to the formation of large DNA fragments involves base substitution or modification of DNA molecules. New restriction sites can be exposed by relaxing the specificity of some restriction endonucleases. Under conditions of relaxed specificity, the recognition sequence shrinks to the core sequence, which is usually two nucleotides shorter than the normal recognition sequence. When the core restriction sequences are unmasked by relaxation of restriction-endonuclease specificity, the normal restriction sequences inaccessible in some DNAs can be exposed by the prevention of DNA modification. All manipulations described here lead to the formation of DNA fragments that are different (large or new) from normal restriction-endonuclease digestion products. These DNA fragments have potential applications in the mapping of DNA, gene-cloning experiments, and genetic experiments on deletion or substitution.

DNA Restriction Enzymes↗
PubMed1979

Ring prosthesis.

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Eye Burns↗
PubMed1978

Effect of dibutyryl cyclic AMP and analogs on the rate of contractions of myocytes in culture.

2O, 6N-butyryl, 3', 5'-cyclic monophosphate (dibu cAMP) when added to fetal rat heart cells in culture inhibits myocyte contraction. This inhibition is 100, 84 and 51% complete when the dibu cAMP concentration used is 2, 0.2 and 0.02 mM, respectively. The potency of dibu cAMP derivatives in myocyte contraction inhibition follows the order, dibu cAMP greater than 6N-bu cAMP greater than 2O-bu cAMP = AMP greater than butyrate. The inhibition caused by the first three chemicals is greater than 70%.

Animals↗
PubMed1978

Relationship between dibutyryl cyclic AMP and microtubule organization in contracting heart muscle cells.

Rhythmic and synchronous contractions of interconnecting myocyte cultures prepared from fetal rat hearts are arrested upon the addition of 0.2--2.0 mM N6, O2'-dibuturyladenosine 3':5'-cyclic monophosphate (Bt2cAMP). The contractions arrested by Bt2cAMP are restored either by diluting the Bt2cAMP from the media or by adding colchicine. While colchicine restores Bt2cAMP-arrested myocyte contractions at concentrations as low as 1.0 micron, the inactive isomer lumicolchicine shows no effect. Morphologically, Bt2cAMP treatment of myocyte cultures results in the appearance of numerous elongated cellular processes not present in control cultures. Ultrastructural examination indicates that in Bt2cAMP-treated cells the intracellular distribution of microtubules is altered such that these organelles appear to accumulate in parallel arrays. In cells not treated with Bt2cAMP, the microtubules appear randomly oriented, while in cells treated with only colchicine, intact microtubules are not observed. The relationship between microtubules an heart cell contraction is discussed.

Animals↗